Two or more drugs administred at the same time may interact with each other. The interactions may be potentiation or antagonism of one drug by another or occasionally some other effect. Drug interactions may be of pharmacokinetic or pharmacodynamic type. The pharmacokinetic interactions can be because of absorption mechanism, competition of two drugs at the protein binding sites, metabolizing enzyme system or excretion. When two or more drugs are concomitantly administered there is always a possibility of pharmacokinetic or pharmacodynamic interaction. The pharmacodynamic interactions can be at the receptor level for competition at same drug target (enzyme/receptor) acting synergistically or antagonizing the effect of each other. The drugs which have narrow therapeutic window have greater potential to cause unexpected adverse effect when their pharmacokinetics or pharmacodynamics is altered. In such situation, the following precautions are advisable:
Antiepileptics, anticoagulants, anticancers, xanthenes, antide pressants, antiarrhythmics etc.
Some representative clinically relevant drug–drug interactions are listed below:
ABCIXIMAB |
|
Anticoagulant |
Increased risk of bleedin |
Antiplatelet agents |
Increased risk of bleedin |
ACETAZOLAMIDE |
|
Carbamazepine |
Increased risk of hyponatraemia; acetazolamide increases plasma–carbamazepine concentration |
Digoxin |
Cardiac toxicity of digoxin increased if hypokalaemia occurs |
Furosemide |
Increased risk of hypokalaemia |
Nifedipine |
Enhanced hypotensive effect |
Phenytoin |
Increased risk of osteomalacia |
ACETYLSALICYLIC ACID |
|
Corticosteroids |
Increased risk of gastrointestinal bleeding and ulceration; corticosteroids reduce plasma–salicylate concentration |
Heparin |
Enhanced anticoagulant effect |
Methotrexate |
Reduced excretion of methotrexate (increased toxicity) |
Warfarin |
Increased risk of bleeding due to antiplatelet effect |
ALENDRONATE |
|
Calcium supplements |
Reduced absorption of alendronate |
Antacids |
Reduced absorption of alendronate |
ALLOPURINOL |
|
Azathioprine |
Effects of azathioprine enhanced with increased toxicity; reduce dose when given with allopurinol |
Mercaptopurine |
Effects of 6-mercaptopurine enhanced with increased toxicity; reduce dose when given with allopurinol |
ALTEPLASE |
|
Prostacyclin, nitrates |
Increased plasma–alteplase clearance |
Abciximab |
Additive effect |
Nitroglycerin |
Decreased thrombolytic effect of alteplase |
Warfarin, Antiplatelet agents |
Increased risk of bleeding |
NSAIDs |
Increased risk of GI bleeding |
AMILORIDE |
|
Artemether + Lumefantrine |
Increased risk of ventricular arrhythmias if electrolyte disturbance occurs |
Cisplatin |
Increased risk of nephrotoxicity and ototoxicity |
Cyclosporine |
Increased risk of hyperkalaemia |
Enalapril |
Enhanced hypotensive effect; risk of severe hyperkalaemia |
AMINOPHYLLINE |
|
Febuxostat |
Increased effect of aminophylline |
Rifamycin |
Decreased effect of aminophylline |
AMITRIPTYLINE |
|
Artemether + Lumefantrine |
Increased risk of ventricular arrhythmias |
Carbamazepine |
Antagonism of anticonvulsant effect |
Haloperidol |
Increased plasma–amitriptyline concentration; increased risk of ventricular arrhythmias |
Phenobarbital |
Antagonism of anticonvulsant effect |
Phenytoin |
Antagonism of anticonvulsant effect |
Valproic acid |
Antagonism of anticonvulsant effect |
AMOXYCILLIN |
|
Methotrexate |
Reduced excretion of methotrexate; increased risk of toxicity |
AMOXYCILLIN + CLAVULANIC ACID |
|
Probenecid |
Increased concentrations of amoxycillin in serum and bile |
Allopurinol |
Occurrence of allergic cutaneous reactions |
Digoxin |
Increased absorption |
Warfarin |
Increased incidence of bleeding |
AMPHOTERICIN B |
|
Corticosteroids |
Increased risk of hypokalaemia |
Cyclosporine |
Increased risk of nephrotoxicity |
Digoxin |
Increased digoxin toxicity if hypokalaemia occurs |
Tacrolimus |
Synergistic effect of amphotercin |
AMPICILLIN |
|
Methotrexate |
Reduced excretion of methotrexate; increased risk of toxicity |
Warfarin |
Studies have failed to demonstrate an interaction, but common experience in anticoagulant clinics is that INR can be altered by a course of ampicillin |
ANTACIDS (Aluminium Hydroxide; Magnesium Hydroxide) |
|
Note: Antacids should preferably not be taken at the same time as other drugs since they may impair absorption |
|
Ciprofloxacin |
Reduced absorption of ciprofloxacin |
Digoxin |
Reduced absorption of digoxin |
Isoniazid |
Reduced absorption of isoniazid |
Phenytoin |
Reduced absorption of phenytoin |
Rifampicin |
Reduced absorption of rifampicin |
ARTEMETHER + LUMEFANTRINE |
|
Amitriptyline |
Increased risk of ventricular arrhythmias |
Azithromycin |
Avoid concomitant use |
Chloroquine |
Increased risk of ventricular arrhythmias |
Ciprofloxacin |
Avoid concomitant use |
Fluconazole |
Avoid concomitant use |
Furosemide |
Increased risk of ventricular arrhythmias if electrolyte disturbance occurs |
Mefloquine |
Increased risk of ventricular arrhythmias |
Ofloxacin |
Avoid concomitant use |
Pyrimethamine |
Avoid concomitant use |
Quinine |
Increased risk of ventricular arrhythmias |
Sulfadoxine + Pyrimethamine |
Avoid concomitant use |
ATENOLOL |
|
Glibenclamide |
Masking of warning signs of hypoglycaemia such as tremor |
Insulins |
Enhanced hypoglycaemic effect; masking of warning signs of hypoglycaemia such as tremor |
Lidocaine |
Increased risk of myocardial depression |
Nifedipine |
Severe hypotension and heart failure occasionally |
Verapamil |
Asystole, severe hypotension and heart failure |
ATORVASTATIN |
|
Ketoconazole |
Increased plasma concentration of atorvastatin and risk of myotoxicity in frequent |
Itraconazole |
Increased plasma concentration of atorvastatin and risk of myotoxicity in frequent |
Ritonavir |
Increased plasma concentration of atorvastatin and risk of myotoxicity in frequent |
Erythromycin |
Increased plasma concentration of atorvastatin and risk of myotoxicity in frequent |
Fibrates |
Increased risk of rhabdomyolysis |
AZATHIOPRINE |
|
Allopurinol |
Effects of azathioprine enhanced |
Phenytoin |
Reduced absorption of phenytoin |
Rifampicin |
Transplants rejected |
Sulfamethoxazole + Trimethoprim |
Increased risk of haematological toxicity |
Vaccines, Live |
Avoid use of live vaccines with azathioprine (impairment of immune response) |
Warfarin |
Reduced effect of anticoagulant |
AZITHROMYCIN |
|
Cyclosporine |
Plasma concentration of cyclosporine increased |
Digoxin |
Effect of digoxin enhanced |
Digoxin |
Effect of digoxin enhanced |
Warfarin |
Enhanced anticoagulant effect of warfarin |
BACLOFEN |
|
Tricyclic antidepressents |
Risk of muscle weakness |
MAO inhibitors |
Depression of brain function as well as low blood pressure |
Antidiabetic drugs |
Increased blood sugar level |
BENZATHINE BENZYLPENICILLIN |
|
Aminoglycosides |
Reduced effect of aminoglycosides in patient with renal impairment |
Methotrexate |
Reduced excretion of methotrexate |
BLEOMYCIN |
|
Vaccines, Live |
Avoid use of live vaccines with bleomycin (impairment of immune response) |
Vinblastine |
Increased risk of cardiovascular toxicity |
BROMOCRIPTINE |
|
Ergot derivatives |
Additive dopamine agonistic activity |
BUDESONIDE |
|
Ketoconazole |
Plasma concentration of orally administered budesonide increased |
Itraconazole |
Metabolism of budesonide inhibited |
Clarithromycin |
Metabolism of budesonide inhibited |
Erythromycin |
Metabolism of budesonide inhibited |
BUPIVACAINE |
|
Lidocaine |
Increased myocardial depression |
Procainamide |
Increased myocardial depression |
Quinidine |
Increased myocardial depression |
BUSULPHAN |
|
Itraconazole |
Increased level of busulphan |
Metronidazole |
Increased level of busulphan |
Nalidixic acid |
Risk of gastrointestinal toxicity |
Thioguanine |
Risk of portal hypertension and espohageal varices |
CALCIUM CARBONATE + VITAMIN D3 |
|
Quinolones |
Risk of decreased absorption into the body |
Tetracycline |
Risk of decreased absorption into the body |
Mycophenolate mofetil |
Decreased effectiveness of mycophenolate mofetil |
CALCIUM SALTS |
|
Digoxin |
Large intravenous doses of calcium can precipitate arrhythmias |
Tetracyclines |
Reduced absorption of tetracyclines |
CAPREOMYCIN |
|
BCG vaccine |
May make the vaccine ineffective |
Neuromuscular blocking agents |
Increase in neuromuscular blocking effects |
Typhoid vaccine |
May make the vaccine ineffective |
CARBAMAZEPINE |
|
Acetazolamide |
Increased risk of hyponatraemia; acetazolamide increases plasma–carbamazepine concentration |
Amitriptyline |
Antagonism (convulsive threshold lowered); accelerated metabolism of amitriptyline; reduced plasma concentration; reduced effect antidepressant |
Chloroquine |
Convulsive threshold occasionally lowered |
Chlorpromazine |
Antagonism of anticonvulsant effect (convulsive threshold lowered) |
Corticosteroids |
Accelerated metabolism of corticosteroids |
Cyclosporine |
Accelerated metabolism (reduced plasma–cyclosporine concentration) |
Diltiazem |
Increased carbamazepine level |
Erythromycin |
Increased plasma–carbamazepine concentration |
Fluphenazine |
Antagonism of anticonvulsant effect (convulsive threshold lowered) |
Haloperidol |
Antagonism of anticonvulsant effect |
Isoniazid |
Increased plasma–carbamazepine concentration (also isoniazid hepatotoxicity increased) |
Lopinavir |
Reduced plasma-lopinavir concentration |
Progestins |
Accelerated metabolism of progestins |
Sulfamethoxazole + Trimethoprim |
May be enhanced toxicity without corresponding increase in antiepileptic effect; plasma concentration of carbamazepine often lowered |
Phenytoin |
May be enhanced toxicity without corresponding increase in antiepileptic effect; plasma concentration of phenytoin often lowered |
Ritonavir |
Plasma concentration increased by ritonavir |
Valproic acid |
Plasma concentration of valproic acid often lowered; plasma concentration of active metabolite of carbamazepine often raised |
Verapamil |
Enhanced effect of carbamazepine |
Warfarin |
Accelerated metabolism of warfarin (reduced anticoagulant effect) |
CEFAZOLIN |
|
Oral anticoagulants |
Increased hypoprothrombinemic effect of anticoagulant. |
CEFIXIME |
|
Carbamazepine |
Elevated carbamazepine levels |
Anticoagulants |
Increased prothrombin time |
CEFTAZIDIME |
|
Furosemide |
Nephrotoxicity of ceftazidime increased |
Warfarin |
Enhanced anticoagulant effect |
CEFTRIAXONE |
|
Warfarin |
Enhanced anticoagulant effect |
CHLORAMPHENICOL |
|
Cyclosporine |
Plasma concentration of cyclosporine increased |
Iron |
Avoid as can cause bone marrow depression which appears treatment of anaemia |
Phenobarbital |
Metabolism of chloramphenicol accelerated (reduced chloramphenicol concentration) |
Phenytoin |
Plasma–phenytoin concentration increased (risk of toxicity) |
Vitamin B12 |
Avoid concomitant use, can cause bone marrow depression |
CHLOROQUINE |
|
Artemether + Lumefantrine |
Increased risk of ventricular arrhythmias |
Carbamazepine |
Convulsive threshold occasionally lowered |
Cyclosporine |
Increased plasma–cyclosporine concentration (increased risk of toxicity) |
Digoxin |
Plasma–digoxin concentration increased |
Mefloquine |
Increased risk of convulsions |
Phenytoin |
Convulsive threshold occasionally lowered |
Valproic acid |
Convulsive threshold occasionally lowered |
CHLORPROMAZINE |
|
Amitriptyline |
Increased antimuscarinic adverse effects; increased plasma-amitriptyline concentration; increased risk of ventricular arrhythmias |
Artemether + Lumefantrine |
Increased risk of ventricular arrhythmias |
Clomipramine |
Increased antimuscarinic adverse effects; increased plasma-clomipramine concentration; increased risk of ventricular arrhythmias |
Ether, Anaesthetic |
Enhanced hypotensive effect |
Halothane |
Enhanced hypotensive effect |
Ketamine |
Enhanced hypotensive effect |
Nitrous oxide |
Enhanced hypotensive effect |
Phenobarbital |
Antagonism of anticonvulsant effect (convulsive threshold lowered) |
Phenytoin |
Antagonism of anticonvulsant effect (convulsive threshold lowered) |
Procainamide |
Increased risk of ventricular arrhythmias |
Propranolol |
Concomitant administration may increase plasma concentration of both drugs; enhanced hypotensive effect |
Quinidine |
Increased risk of ventricular arrhythmias |
Ritonavir |
Plasma concentration increased by ritonavir |
Thiopental |
Enhanced hypotensive effect |
Valproic acid |
Antagonism of anticonvulsant effect (convulsive threshold lowered) |
CINNARIZINE |
|
CNS depressants (alcohol, barbiturates, hypnotics, narcotic analgesics, tricyclic antidepressants, sedatives and tranquillizers) |
Additive sedation |
Zolpidem |
Additive toxicity |
CIPROFLOXACIN |
|
Artemether + Lumefantrine |
Avoid concomitant use |
Cyclosporine |
Increased risk of nephrotoxicity |
Glibenclamide |
Enhanced effect of glibenclamide |
Ibuprofen |
Increased risk of convulsions |
Warfarin |
Enhanced anticoagulant effect |
CISPLATIN |
|
Aminoglycoside antibiotics |
Increased risk of nephrotoxicity and ototoxicity |
Furosemide |
Increased risk of nephrotoxicity and ototoxicity |
Hydrochlorothiazide |
Increased risk of nephrotoxicity and ototoxicity |
Vancomycin |
Increased risk of nephrotoxicity and ototoxicity |
CLARITHROMYCIN |
|
Oral anticoagulants |
Increased anticoagulant effect. |
Carbamazepine |
Increased serum concentration of carbamazepine. |
Digoxin |
Increased concentration of digoxin. |
Lovastatin |
Avoid concomitant use |
Sildenafil |
Dose reduction of sildenafil may be required. |
Simvastatin |
Avoid concomitant use |
Sirolimus |
Elevation in serum sirolimus level |
Tacrolimus |
Elevation in serum sirolimus level |
Tadalafil |
Dose reduction of tadalafil may be required. |
CLINDAMYCIN |
|
Erythromycin |
Antagonist activity |
Pancuronium |
Neuromuscular blockade exaggerated |
Kaoli-pectin |
Reduced absorption rate |
Gentamycin |
Synergistic effect |
CLOBAZAM |
|
Cimetidine |
Increased effect of clobazam |
Barbiturates |
Decreased serum level of clobazam |
CLONAZEPAM |
|
Carbamazepine |
Decreased level of carbamazepine |
Ketoconazole |
Inhibition of metabolism of clonazepam |
CLOPIDOGREL |
|
Omeprazole |
Plasma concentration of active metabolite of clopidogrel is decreased |
NSAIDs |
Increased risk of gastrointestinal bleeding |
CLONIDINE |
|
Beta blockers |
Sinus bradycardia, monitor heart rate |
Clomipramine |
Risk of hypertensive crisis |
CLONIDINE |
|
Diazepam |
Enhanced sedative effect |
Ritonavir |
Ritonavir increases plasma concentration of codeine |
CORTICOSTEROIDS |
|
Acetylsalicylic acid |
Increased risk of gastrointestinal bleeding and ulceration; hydrocortisone reduces plasma-salicylate concentration |
Amphotericin B |
Increased risk of hypokalaemia |
Atenolol |
Antagonism of hypotensive effect |
Carbamazepine |
Accelerated metabolism of hydrocortisone (reduced effect) |
Digoxin |
Increased risk of hypokalaemia |
Enalapril |
Antagonism of hypotensive effect |
Furosemide |
Antagonism of diuretic effect; increased risk of hypokalaemia |
Glibenclamide |
Antagonism of hypoglycaemic effect |
Hydrochlorothiazide |
Antagonism of diuretic effect; increased risk of hypokalaemia |
Insulins |
Antagonism of hypoglycaemic effect |
Levonorgestrel |
Levonorgestrel increases plasma concentration of corticosteroids |
Methotrexate |
Increased risk of haematological toxicity |
Nifedipine |
Antagonism of hypotensive effect |
Phenobarbital |
Metabolism of hydrocortisone accelerated (reduced effect) |
Phenytoin |
Metabolism of hydrocortisone accelerated (reduced effect) |
Rifampicin |
Accelerated metabolism of corticosteroids (reduced effect) |
Salbutamol |
Increased risk of hypokalaemia if high doses of corticosteroids given with high doses of salbutamol |
Warfarin |
Anticoagulant effect altered |
CYCLOPHOSPHAMIDE |
|
Vaccines, Live |
Avoid use of live vaccines with cyclophosphamide (impairment of immune response) |
CYCLOSPORINE |
|
Amphotericin B |
Increased risk of nephrotoxicity |
Ciprofloxacin |
Increased risk of nephrotoxicity |
Digoxin |
Reduced clearance of digoxin (risk of toxicity) |
Enalapril |
Increased risk of hyperkalaemia |
Erythromycin |
Increased plasma-cyclosporine concentration |
Methotrexate |
Increased toxicity |
Metoclopramide |
Plasma-cyclosporine concentration increased |
Ofloxacin |
Increased risk of nephrotoxicity |
Phenobarbital |
Metabolism of cyclosporine accelerated |
Phenytoin |
Accelerated metabolism |
Rifampicin |
Accelerated metabolism (reduced plasma-cyclosporine concentration) |
Ritonavir |
Plasma concentration increased by ritonavir |
Rosuvastatin |
Marked rise in serum rosuvastatin level |
Sulfonamides and Trimethoprim |
Increased toxicity |
Vaccines, Live |
Avoid use of live vaccines with cyclosporine |
Vancomycin |
Increased risk of nephrotoxicity |
DANAZOL |
|
Anticoagulants (warfarin ) |
Danazol inhibits metabolism of coumarins |
Cyclosporine |
Danazol inhibits metabolism of cyclosporine |
Lovastatin |
Increased risk of myopathy |
Simvastatin |
Increased risk of myopathy |
Tacrolimus |
Danazol increases plasma concentration of tacrolimus |
DAPSONE |
|
Rifampicin |
Reduced plasma-dapsone concentration |
Sulfamethoxazole + Trimethoprim |
Plasma concentration of both dapsone and trimethoprim increased with concomitant use |
DESFERRIOXAMINE MESYLATE |
|
Ascorbic acid |
May worsen iron toxicity |
DEXAMETHASONE |
|
Acetazolamide |
Increased risk of hypokalaemia; antagonism of diuretic effect |
Acetylsalicylic acid |
Increased risk of gastrointestinal bleeding and ulceration; dexamethasone reduces plasma-salicylate concentration |
Albendazole |
Plasma-albendazole concentration increased |
Amiloride |
Antagonism of diuretic effect |
Amphotericin B |
Increased risk of hypokalaemia (avoid concomitant use unless dexamethasone needed to control reactions) |
Atenolol |
Antagonism of hypotensive effect |
Carbamazepine |
Accelerated metabolism of dexamethasone (reduced effect) |
Digoxin |
Increased risk of hypokalaemia |
Enalapril |
Antagonism of hypotensive effect |
Ephedrine |
Metabolism of dexamethasone accelerated |
Erythromycin |
Erythromycin inhibits metabolism of dexamethasone |
Furosemide |
Antagonism of diuretic effect; increased risk of hypokalaemia |
Glibenclamide |
Antagonism of hypoglycaemic effect |
Glyceryl trinitrate |
Antagonism of hypotensive effect |
Hydralazine |
Antagonism of hypotensive effect |
Hydrochlorothiazide |
Antagonism of diuretic effect; increased risk of hypokalaemia |
Ibuprofen |
Increased risk of gastrointestinal bleeding and ulceration |
Indinavir |
Reduced plasma-indinavir concentration |
Insulins |
Antagonism of hypoglycaemic effect |
Isosorbide dinitrate |
Antagonism of hypotensive effect |
Levonorgestrel |
Levonorgestrel increases plasma concentration of dexamethasone |
Lopinavir |
Reduced plasma-lopinavir concentration |
Medroxyprogesterone |
Medroxyprogesterone increases plasma concentration of dexamethasone |
Metformin |
Antagonism of hypoglycaemic effect |
Methotrexate |
Increased risk of haematological toxicity |
Methyldopa |
Antagonism of hypotensive effect |
Nifedipine |
Antagonism of hypotensive effect |
Norethisterone |
Norethisterone increases plasma concentration of dexamethasone |
Phenobarbital |
Metabolism of dexamethasone accelerated (reduced effect) |
Phenytoin |
Metabolism of dexamethasone accelerated (reduced effect) |
Praziquantel |
Plasma-praziquantel concentration reduced |
Propranolol |
Antagonism of hypotensive effect |
Rifampicin |
Accelerated metabolism of dexamethasone (reduced effect) |
Ritonavir |
Increased plasma concentration by ritonavir |
Salbutamol |
Increased risk of hypokalaemia if high doses of dexamethasone given with high doses of salbutamol |
Saquinavir |
Reduced plasma-saquinavir concentration |
Sodium nitroprusside |
Antagonism of hypotensive effect |
Spironolactone |
Antagonism of diuretic effect |
Theophylline |
Increased risk of hypokalaemia |
Vaccines, Live |
High doses of dexamethasone impair immune response; avoid use of live vaccines |
Verapamil |
Antagonism of hypotensive effect |
Warfarin |
Anticoagulant effect altered |
DEXTRAN 40 |
|
Abciximab |
Additive effect |
DEXTROMETHORPHAN |
|
MAO Inhibitors |
Risk of hypotension, hyperpyrexia, sedation etc. |
Sibutramine |
Risk of serotonin syndrome |
DIAZEPAM |
|
Atenolol |
Enhanced hypotensive effect |
Enalapril |
Enhanced hypotensive effect |
Furosemide |
Enhanced hypotensive effect |
Glyceryl trinitrate |
Enhanced hypotensive effect |
Ritonavir |
Plasma concentration increased by ritonavir |
DICLOFENAC |
|
Cyclosporine |
Decreased renal function |
Methotrexate |
Increased levels of methotrexate. |
DICYCLOMINE |
|
Antidepressants |
Increased risk of antimuscarinic side effects |
Antipsychotics |
Antimuscarinics reduce effects of haloperidol; increased risk of antimuscarinic side-effects when antimuscarinics given with clozapine; antimuscarinics reduce plasma concentration of phenothiazines, but risk of antimuscarinic side effects increased |
DIDANOSINE |
|
Divalproex |
Risk of additive toxicity |
Ganciclovir |
Increased didanosine concentration |
Metronidazole |
Risk of additive toxicity |
Pentamidine |
Risk of additive toxicity |
Stavudine |
Risk of additive toxicity |
Vinblastine |
Risk of additive toxicity |
DIGOXIN |
|
Acetazolamide |
Cardiac toxicity of digoxin increased if hypokalaemia occurs |
Amphotericin B |
Increased digoxin toxicity if hypokalaemia occurs |
Atenolol |
Increased AV block and bradycardia |
Corticosteroids |
Increased risk of hypokalamia |
Cyclosporine |
Reduced clearance of digoxin (risk of toxicity) |
Furosemide |
Cardiac toxicity of digoxin increased if hypokalaemia occurs |
Hydrochlorothiazide |
Cardiac toxicity of digoxin increased if hypokalaemia occurs |
Nifedipine |
Increased plasma concentration of digoxin |
Timolol |
Increased AV block and bradycardia |
Verapamil |
Increased plasma concentration of digoxin; increased AV block and bradycardia |
DIHYDROERGOTAMINE |
|
Amiodarone |
Increased cardiac depressant effects |
Azoles antifungal |
Increased level of alkoloid |
Buspirone |
Increased serum level of buspirone |
Macrolide antibiotics |
Increased plasma level of unchanged alkaloid and peripheral vasoconstriction |
Protease inhibitors |
Elevated levels of ergot alkaloids |
Sumatriptan |
Additive effect with dihydroergotamine |
DILTIAZEM |
|
Carbamazepine |
Increased serum level of carbamazepine |
Rifampin |
Decreased diltiazem plasma concentration |
DOBUTAMINE |
|
Beta-blockers |
Risk of peripheral resistance |
DOMPERIDONE |
|
Amiodarone |
Additive toxicity with amiodarone |
DOPAMINE |
|
Ergometrine |
Increased risk of ergotism |
Haloperidol |
Antagonism of pressor action |
DOXORUBICIN |
|
Cyclosporine |
Increased risk of neurotoxicity |
Cyclophosphamide |
Chances of exacerbation of cyclophosphamide-induced hemorrhagic cystitis |
Digoxin |
Decreased digoxin levels |
Paclitaxel |
Increased risk of cardiotoxicity |
Progesterone |
Increased risk of doxorubicin-induced neutropenia |
Quinidine |
Increases the levels of doxorubicin |
Stavudine |
Decreased level and effectiveness of stavudine |
Vaccines, Live |
Avoid use of live vaccines with doxorubicin |
Zidovudine |
Decreased effect of zidovudine |
DOXYCYCLINE |
|
Cyclosporine |
Increased plasma-cyclosporine concentration |
Ergotamine |
Increased risk of ergotism |
Warfarin |
Anticoagulant effect enhanced |
EFAVIRENZ |
|
Ergot derivatives |
Increased chance of ergotism |
Itraconazole |
Decreased plasma level of itraconazole |
Lopinavir |
Plasma concentration of lopinavir reduced |
Ritonavir |
Increased risk of toxicity |
ENALAPRIL |
|
Acetylsalicylic acid |
Antagonism of hypotensive effect; increased risk of renal impairment |
Antacids |
Absorption of enalapril reduced |
Cyclosporine |
Increased risk of hyperkalaemia |
Glibenclamide |
Hypoglycaemic effect enhanced |
Heparin |
Increased risk of hyperkalaemia |
Lithium |
Increased plasma-lithium concentration |
Spironolactone |
Enhanced hypotensive effect, risk of severe hyperkalaemia |
EPINEPHRINE (ADRENALINE) |
|
Halothane |
Risk of arrhythmias |
ERYTHROMYCIN |
|
Artemether + Lumefantrine |
Avoid concomitant use |
Carbamazepine |
Increased plasma-carbamazepine concentration |
Corticosteroids |
Inhibits metabolism of corticosteroids |
Cyclosporine |
Increased plasma-cyclosporine concentration |
Digoxin |
Enhanced effect of digoxin |
Warfarin |
Enhanced anticoagulant effect |
ERYTHROPOIETIN |
|
Haematinics |
Enhanced efficiency of erythropoietin |
ESCITALOPRAM |
|
Carbamazepine |
Carbamazepine toxicity may be precipitated |
ESMOLOL |
|
Verapamil |
Chances of cardiac arrest |
ETHINYL ESTRADIOL |
|
Hydantoin |
Reduced effect of estrogen |
ETOPOSIDE |
|
Vaccines, Live |
Avoid use of live vaccines with etoposide |
EZETIMIBE |
|
Bile Acid Sequestrants |
Decreased levels and clinical effectiveness of ezetimibe |
Fibrates |
Elevated levels of ezetimibe leading to toxicity |
Cyclosporine |
Increased ezetimibe levels in patients with severe renal insufficiency |
FACTOR IX |
|
Acetylsalicylic acid |
Risk of bleeding |
FAMOTIDINE |
|
Antacids |
Reduced absorption of famotidine |
Ketoconazole, itraconazole |
Reduced absorption of ketoconazole and itraconazole |
Ethanol |
Gastric mucosal irritation may occur |
FENOFIBRATE |
|
Anticoagulants |
Increased effect of anticoagulants |
Statins |
Increased risk of kidney and muscle problems |
Cyclosporine |
Increased risk of nephrotoxicity |
IRON SALTS |
|
Ciprofloxacin |
Absorption of ciprofloxacin reduced by oral ferrous salts |
Doxycycline |
Reduced absorption of oral ferrous salts by doxycycline; reduced absorption of doxycycline by oral ferrous salts |
Methyldopa |
Reduced hypotensive effect of methyldopa |
FEXOFENADINE |
|
Antacids |
Decreased absorption of fexofenadine |
Erythromycin |
Increased plasma concentration of fexofenadine |
Ketoconazole |
Increased plasma concentration of fexofenadine |
FLUCONAZOLE |
|
Artemether + Lumefantrine |
Avoid concomitant use |
Cyclosporine |
Metabolism of cyclosporine inhibited |
Glibenclamide |
Plasma concentration of glibenclamide increased |
Rifampicin |
Accelerated metabolism of fluconazole |
Warfarin |
Enhanced anticoagulant effect |
Zidovudine |
Increased plasma concentration of zidovudine (increased risk of toxicity) |
FLUCYTOSINE |
|
Amphotericin B |
Renal excretion of flucytosine decreased and cellular uptake increased (flucytosine toxicity increased) |
5-FLUOROURACIL |
|
Metronidazole |
Metabolism of 5-fluorouracil inhibited |
Phenytoin |
Reduced absorption of phenytoin |
Warfarin |
Anticoagulant effect enhanced |
FLUOXETINE |
|
Benzodiazepines |
Increased level of benzodiazepines |
Clozapine |
Increased levels of clozapine |
Selected MAO inhibitors |
Risk of serotonin syndrome |
FLUPHENAZINE |
|
Amitriptyline |
Increased antimuscarinic adverse effects; increased plasma-amitriptyline concentration; increased risk of ventricular arrhythmias |
Artemether + Lumefantrine |
Increased risk of ventricular arrhythmias |
Atenolol |
Enhanced hypotensive effect |
Carbamazepine |
Antagonism of anticonvulsant effect |
Enalapril |
Enhanced hypotensive effect |
Lithium |
Increased risk of extrapyramidal effects and neurotoxicity |
Methyldopa |
Enhanced hypotensive effect; increased risk of extrapyramidal effects |
Metoclopramide |
Increased risk of extrapyramidal effects |
Nifedipine |
Enhanced hypotensive effect |
Phenobarbital |
Antagonism of anticonvulsant effect (convulsive threshold lowered) |
Phenytoin |
Antagonism of anticonvulsant effect (convulsive threshold lowered) |
Valproic acid |
Antagonism of anticonvulsant effect (convulsive threshold lowered) |
FOLIC ACID AND FOLINIC ACID |
|
Phenobarbital |
Plasma concentration of phenobarbital reduced |
Phenytoin |
Plasma-phenytoin concentration reduced |
FORMOTEROL + FLUTICASONE PROPIONATE |
|
Ritonavir |
Systemic corticosteroid effects including cushing syndrome and adrenal suppression |
Ketoconazole |
Increased plasma fluticasone propionate concentrations |
MAO inhibitors |
Increased risk of cardiovascular adverse effects |
FOSPHENYTOIN |
|
Albendazole |
Efficacy is impaired by phenytoin |
Antipsychotics |
Efficacy is impaired by phenytoin |
Furosemide |
Efficacy is impaired by phenytoin |
Quinidine |
Efficacy is impaired by phenytoin |
Theophylline |
Efficacy is impaired by phenytoin |
Vitamin D |
Efficacy is impaired by phenytoin |
FRAMYCETIN |
|
Capreomycin |
Additive toxicity with capreomycin |
FURAZOLIDONE |
|
SSRIs |
Risk of serotonin syndrome |
FUROSEMIDE |
|
Amphotericin B |
Increased risk of hypokalaemia |
Artemether + Lumefantrine |
Increased risk of ventricular arrhythmias if electrolyte disturbance occurs |
Cisplatin |
Increased risk of nephrotoxicity and ototoxicity |
Digoxin |
Cardiac toxicity of digoxin increased if hypokalaemia occurs |
Enalapril |
Enhanced hypotensive effect |
Glibenclamide |
Antagonism of hypoglycaemic effect |
Corticosteroids |
Antagonism of diuretic effect; increased risk of hypokalaemia |
Lithium |
Increased plasma-lithium concentration and risk of toxicity |
Salbutamol |
Increased risk of hypokalaemia with high doses of salbutamol |
Streptomycin |
Increased risk of ototoxicity |
Vancomycin |
Increased risk of ototoxicity |
GEMCITABINE |
|
Live vaccines |
Serum antibody response may not be obtained |
Zidovudine |
Additive toxicity |
GENTAMICIN |
|
Cyclosporine |
Increased risk of nephrotoxicity |
Cisplatin |
Increased risk of nephrotoxicity and ototoxicity |
Suxamethonium |
Enhanced muscle relaxant effect |
Vancomycin |
Increased risk of nephrotoxicity and ototoxicity |
Vecuronium |
Enhanced muscle relaxant effect |
GLIBENCLAMIDE |
|
Ciprofloxacin |
Enhanced effect of glibenclamide |
Corticosteroids |
Antagonism of hypoglycaemic effect |
Enalapril |
Hypoglycaemic effect enhanced |
Fluconazole |
Plasma concentration of glibenclamide increased |
Hydrochlorothiazide |
Antagonism of hypoglycaemic effect |
Levonorgestrel |
Antagonism of hypoglycaemic effect |
Sulfadoxine + Pyrimethamine |
Effect of glibenclamide may be enhanced |
Sulfamethoxazole + Trimethoprim |
Effect of glibenclamide may be enhanced |
Warfarin |
Enhanced hypoglycaemic effects and changes to anticoagulant effect |
GLICLAZIDE |
|
Acetylsalicylic acid |
Effect of gliclazide is potentiated |
Clofibrate |
Effect of gliclazide is potentiated |
Sulphonamides |
Effect of gliclazide is potentiated |
Oral anticoagulants |
Effect of gliclazide is potentiated |
MAO inhibitors |
Effect of gliclazide is potentiated |
Rifampicin |
Effect of gliclazide is antagonized |
Barbiturates |
Effect of gliclazide is antagonized |
Diuretics |
Effect of gliclazide is antagonized |
Diazoxide |
Effect of gliclazide is antagonized |
Glucocorticoids |
Effect of gliclazide is antagonized |
Sympathomimetics |
Effect of gliclazide is antagonized |
GLIMEPIRIDE |
|
Corticosteroids |
Reduced hypoglycaemic action |
Phenytoin |
Reduced hypoglycaemic action |
Thiazides |
Reduced hypoglycaemic action |
GLUCAGON |
|
Anticoagulants |
Excess hypoprothrombinemia and bleeding complications |
GLYCERYL TRINITRATE |
|
Atenolol |
Enhanced hypotensive effect |
Corticosteroids |
Antagonism of hypotensive effect |
GRISEOFULVIN |
|
Levonorgestrel |
Accelerated metabolism of levonorgestrel (reduced contraceptive effect) |
Warfarin |
Metabolism of warfarin accelerated (reduced anticoagulant effect) |
HALOPERIDOL |
|
Amitriptyline |
Increased plasma-amitriptyline concentration; increased risk of ventricular arrhythmias |
Carbamazepine |
Antagonism of anticonvulsant effect; metabolism of haloperidol accelerated |
Lithium |
Increased risk of extrapyramidal effects and neurotoxicity |
Metoclopramide |
Increased risk of extrapyramidal effects |
Phenobarbital |
Antagonism of anticonvulsant effect; metabolism of haloperidol accelerated |
Phenytoin |
Antagonism of anticonvulsant effect (convulsive threshold lowered) |
Rifampicin |
Accelerated metabolism of haloperidol (reduced plasma-haloperidol concentration) |
Valproic acid |
Antagonism of anticonvulsant effect (convulsive threshold lowered) |
HALOTHANE |
|
Amitriptyline |
Increased risk of arrhythmias and hypotension |
Atenolol |
Enhanced hypotensive effect |
Diazepam |
Enhanced sedative effect |
Levodopa |
Risk of arrhythmias |
Vancomycin |
Hypersensitivity-like reactions can occur with concomitant intravenous vancomycin |
Verapamil |
Enhanced hypotensive effect and AV delay |
HEPARIN |
|
Acetylsalicylic acid |
Enhanced anticoagulant effect |
Enalapril |
Increased risk of hyperkalaemia |
HYDRALAZINE |
|
Corticosteroids |
Antagonism of hypotensive effect |
HYDROCHLOROTHIAZIDE |
|
Amitriptyline |
Increased risk of postural hypotension |
Amphotericin B |
Increased risk of hypokalaemia |
Artemether + Lumefantrine |
Increased risk of ventricular arrhythmias if electrolyte disturbance occurs |
Carbamazepine |
Increased risk of hyponatraemia |
Cisplatin |
Increased risk of nephrotoxicity and ototoxicity |
Digoxin |
Cardiac toxicity of digoxin increased if hypokalaemia occurs |
Glibenclamide |
Antagonism of hypoglycaemic effect |
Ibuprofen |
Risk of nephrotoxicity of ibuprofen increased; antagonism of diuretic effect |
Insulins |
Antagonism of hypoglycaemic effect |
Lithium |
Reduced lithium excretion (increased plasma-lithium concentration and risk of toxicity); furosemide safer than hydrochlorothiazide |
Salbutamol |
Increased risk of hypokalaemia with high doses of salbutamol |
IBUPROFEN |
|
Acetylsalicylic acid |
Avoid concurrent administration (increased adverse effects including gastrointestinal damage); antiplatelet effect of acetylsalicylic acid reduced |
Atenolol |
Antagonism of hypotensive effect |
Cyclosporine |
Increased risk of nephrotoxicity |
Ciprofloxacin |
Increased risk of convulsions |
Corticosteroids |
Increased risk of gastrointestinal bleeding and ulceration |
Digoxin |
Exacerbation of heart failure, reduced GFR, and increased plasma-digoxin concentration |
Enalapril |
Antagonism of hypotensive effect, increased risk of renal impairment |
Glibenclamide |
Enhanced effect of glibenclamide |
Hydrochlorothiazide |
Risk of nephrotoxicity of ibuprofen increased; antagonism of diuretic effect |
Lithium |
Reduced excretion of lithium |
Methotrexate |
Excretion of methotrexate reduced |
Nifedipine |
Antagonism of hypotensive effect |
Warfarin |
Anticoagulant effect enhanced |
Zidovudine |
Increased risk of haematological toxicity |
IMATINIB |
|
Rifampin |
Increased clearance of imatinib |
Warfarin |
Imatinib may inhibit metabolism of warfarin |
IMIPENEM + CILASTATIN |
|
Ganciclovir |
May result in generalised seizures |
INDINAVIR |
|
Carbamazepine |
Reduced plasma concentration of indinavir |
Efavirenz |
Reduced plasma concentration of indinavir |
Ergotamine |
Increased risk of ergotism (avoid concomitant use) |
Nelfinavir |
Combination may lead to increased plasma concentration of either drug (or both) |
Nevirapine |
Reduced plasma concentration of indinavir |
Phenobarbital |
Reduced plasma concentration of indinavir |
Rifampicin |
Metabolism enhanced by rifampicin |
INSULINS |
|
Atenolol |
Enhanced hypoglycaemic effect; masking of warning signs of hypoglycaemia such as tremor |
Corticosteroids |
Antagonism of hypoglycaemic effect |
Enalapril |
Hypoglycaemic effect enhanced |
Furosemide |
Antagonism of hypoglycaemic effect |
Hydrochlorothiazide |
Antagonism of hypoglycaemic effect |
Levonorgestrel |
Antagonism of hypoglycaemic effect |
Nifedipine |
Occasionally impaired glucose tolerance |
IODINE |
|
Lithium |
Synergistic toxicity |
IOPANOIC ACID |
|
Atenolol |
Iopanoic acid toxicity may occur |
Methotrexate |
Methotrexate toxicity may occur |
ISONIAZID |
|
Carbamazepine |
Increased plasma-carbamazepine concentration |
Diazepam |
Metabolism of diazepam inhibited |
Phenytoin |
Metabolism of phenytoin inhibited |
ISOSORBIDE DINITRATE |
|
Sildenafil |
Serious hypotension; MI may be precipitated |
ISOTRETINOIN |
|
Vitamin A |
Additive toxicity |
Progesterone |
Decreased efficacy of microdosed progesterone |
Corticosteroids, phenytoin |
Increased risk of osteoporosis |
Carbamazepine |
Decreased plasma levels of carbamazepine |
Tetracyclines |
Increased risk of pseudotumor cerebri |
ISPAGHULA |
|
Lithium |
decreased effect of lithium |
IVERMECTIN |
|
Vitamin K Antagonists (e.g., warfarin) |
Enhanced anticoagulant effect |
KETOCONAZOLE |
|
Amphotericin B |
Increased adverse effect |
Cyclosporine |
Increased level of cyclosporine |
Tolbutamide |
Reduces blood glucose level |
LAMIVUDINE |
|
Foscarnet |
Concurrent use not recommended |
LATANOPROST |
|
Thiomersal |
Risk of precipitate formation |
LEFLUNOMIDE |
|
Acenocoumarol |
Increased anticoagulant effect |
Warfarin |
Increased anticoagulant effect |
Methotrexate |
Increased risk of hepatotoxicity |
Cholestyramine |
Enhanced leflunomide excretion and increased total clearance by approximately 50% |
LEVOCETIRIZINE |
|
Alcohol or CNS depressants |
Additive sedation |
Theophylline |
Increases the levels of levocetirizine in blood |
LEVODOPA |
|
Metoclopramide |
Antagonism of effects of levodopa |
Ether, Anaesthetic |
Risk of arrhythmias |
Ferrous salts |
Absorption of levodopa may be reduced |
Halothane |
Risk of arrhythmias |
Methyldopa |
Enhanced hypotensive effect; antagonism of antiparkinsonian effect |
Nifedipine |
Enhanced hypotensive effect |
Propranolol |
Enhanced hypotensive effect |
Pyridoxine |
Antagonism of levodopa unless carbidopa also given |
LEVOTHYROXINE |
|
Phenobarbital |
Metabolism of levothyroxine accelerated (may increase levothyroxine requirements in hypothyroidism) |
Theophylline |
Metabolism of theophylline is increased; larger doses are required |
Warfarin |
Enhanced anticoagulant effect |
LIDOCAINE |
|
Acetazolamide |
Action of lidocaine antagonised by hypokalaemia |
Atenolol |
Increased risk of myocardial depression |
Bupivacaine |
Increased myocardial depression |
Furosemide |
Action of lidocaine antagonised by hypokalaemia |
Hydrochlorothiazide |
Action of lidocaine antagonised by hypokalaemia |
Procainamide |
Increased myocardial depression |
Propranolol |
Increased risk of myocardial depression; increased risk of lidocaine toxicity |
Quinidine |
Increased myocardial depression |
Timolol |
Increased risk of myocardial depression |
Verapamil |
Increased risk of myocardial depression |
LITHIUM |
|
Acetazolamide |
Excretion of lithium increased |
Amiloride |
Reduced lithium excretion (increased plasma-lithium concentration and risk of toxicity) |
Enalapril |
Enalapril reduces excretion of lithium (increased plasma-lithium concentration) |
Furosemide |
Reduced lithium excretion (increased plasma-lithium concentration and risk of toxicity); furosemide safer than hydrochlorothiazide |
Haloperidol |
Increased risk of extrapyramidal effects and possibility of neurotoxicity |
Hydrochlorothiazide |
Reduced lithium excretion (increased plasma-lithium concentration and risk of toxicity); furosemide safer than hydrochlorothiazide |
Ibuprofen |
Reduced excretion of lithium (risk of toxicity) |
Methyldopa |
Neurotoxicity may occur without increased plasma-lithium concentration |
Spironolactone |
Reduced lithium excretion (increased plasma-lithium concentration and risk of toxicity) |
Suxamethonium |
Enhanced muscle relaxant effect |
LOPERAMIDE |
|
Quinidine |
Increased CNS level of loperamide |
MEBENDAZOLE |
|
Carbamazepine |
Reduced plasma-mebendazole concentration (increase mebendazole dose for tissue infection) |
Phenytoin |
Reduced plasma-mebendazole concentration (increase mebendazole dose for tissue infection) |
MEFENAMIC ACID |
|
Warfarin |
Risk of serious GI bleeding higher than users of either drug alone. |
Lithium |
Reduced renal clearance and increased risk of lithium toxicity. |
Methotrexate |
Reduced excretion of methotrexate and possible increased risk of toxicity |
Phenobarbital |
Reduced plasma-mebendazole concentration (increase mebendazole dose for tissue infection) |
6-MERCAPTOPURINE |
|
Allopurinol |
Effects of 6-mercaptopurine enhanced with increased toxicity, reduce dose when given with allopurinol |
Phenytoin |
Reduced absorption of phenytoin |
Sulfamethoxazole + Trimethoprim |
Increased risk of haematological toxicity |
Sulfasalazine |
Increased risk of leukopenia |
Trimethoprim |
Increased risk of haematological toxicity |
Vaccines, Live |
Avoid use of live vaccines with 6-mercaptopurine (impairment of immune response) |
Warfarin |
Anticoagulant effect reduced |
MEROPENEM |
|
Probenecid |
Renal excretion of meropenem is inhibited |
Valproic acid |
Serum valproic acid concentration is decreased |
METFORMIN |
|
Atenolol |
Masking of warning signs of hypoglycaemia such as tremor |
Corticosteroids |
Antagonism of hypoglycaemic effect |
Enalapril |
Hypoglycaemic effect enhanced |
Levonorgestrel |
Antagonism of hypoglycaemic effect |
Lithium |
May occasionally impair glucose tolerance |
Medroxyprogesterone |
Antagonism of hypoglycaemic effect |
Norethisterone |
Antagonism of hypoglycaemic effect |
METHADONE |
|
Cimetidine |
Effect of methadone may be increased |
MAO Inhibitors |
Risk of hypotension, hyperexia etc. |
METHOTREXATE |
|
Acetylsalicylic acid |
Reduced excretion of methotrexate (increased toxicity) |
Amoxycillin |
Reduced excretion of methotrexate (increased risk of toxicity) |
Cyclosporine |
Increased toxicity |
Ibuprofen |
Excretion of methotrexate reduced (increased risk of toxicity) |
Nitrous oxide |
Increased antifolate effect (avoid concomitant use) |
Phenytoin |
Reduced absorption of phenytoin; antifolate effect of methotrexate increased |
Pyrimethamine |
Antifolate effect of methotrexate increased |
Sulfadoxine + Pyrimethamine |
Antifolate effect of methotrexate increased; risk of methotrexate toxicity increased |
Sulfamethoxazole + Trimethoprim |
Antifolate effect of methotrexate increased (avoid concomitant use); risk of methotrexate toxicity increased |
Trimethoprim |
Antifolate effect of methotrexate increased (avoid concomitant use) |
Vaccines, Live |
Avoid use of live vaccines with methotrexate (impairment of immune response) |
METHYLDOPA |
|
Ferrous salts |
Reduced hypotensive effect of methyldopa |
Propranolol |
Enhanced hypontensive effect |
METHYL PREDNISOLONE |
|
Amphotericin B |
Chances of potentiation of K+ concentration |
Cyclosporine |
Levels increased upto 2 fold |
METRONIDAZOLE |
|
Phenytoin |
Metabolism of phenytoin inhibited (increased plasma-phenytoin concentration) |
Warfarin |
Enhanced anticoagulant effect |
MMR vaccine |
See vaccines, live |
MIDAZOLAM |
|
Ketoconazole |
Increased levels of midazolam |
Verapamil |
Increased levels of midazolam |
MIFEPRISTONE |
|
Dexamethasone |
Decreased serum levels of mifepristone |
MOMETASONE |
|
Anticoagulants |
Increased or decreased effects of anticoagulants |
Bupropion |
Increased risk of seizures |
Quinolones |
Increased risk of tendonitis and/or tendon rupture |
Quetiapine |
Decreased levels of quetiapine |
MORPHINE |
|
Ciprofloxacin |
Avoid premedication with morphine (reduced plasma-ciprofloxacin concentration) |
Quinidine |
Decreased analgesic effect |
Ritonavir |
Ritonavir increases plasma concentration of morphine |
MYCOPHENOLATE |
|
Bile acid sequestrants |
Decreased level and clinical effect of mycophenolate |
Antacids |
Decreased effect |
NALIDIXIC ACID |
|
Cyclosporine |
Increased risk of nephrotoxicity |
Ibuprofen |
Increased risk of convulsions |
Theophylline |
Increased risk of convulsions |
Warfarin |
Enhanced anticoagulant effect |
NELFINAVIR |
|
Ergotamine |
Increased risk of ergotism (avoid concomitant use) |
Phenobarbital |
Plasma concentration of nelfinavir reduced |
Quinidine |
Increased risk of ventricular arrhythmias (avoid concomitant use) |
Rifampicin |
Plasma concentration of nelfinavir significantly reduced (avoid concomitant use) |
NEOSTIGMINE |
|
Gentamicin |
Antagonism of effect of neostigmine |
Streptomycin |
Antagonism of effect of neostigmine |
NEVIRAPINE |
|
Lopinavir |
Plasma concentration of lopinavir reduced |
Rifampicin |
Reduced plasma concentration of nevirapine (avoid concomitant use) |
Saquinavir |
Plasma concentration of saquinavir reduced (avoid concomitant use) |
NICOTINIC ACID |
|
Ganglionic blocking agents and vasoactive drugs |
Potentiates the effects of ganglionic blocking agents and vasoactive drugs resulting in postural hypotension |
Bile acid sequest (for example, cholestyramine) |
Bind and prevent absorption of niacin; should be separated by 4 to 6 h. |
NIFEDIPINE |
|
Atenolol |
Severe hypotension and heart failure occasionally |
Cyclosporine |
Increased plasma-nifedipine concentration (increased risk of adverse effects such as gingival hyperplasia) |
Digoxin |
Increased plasma concentration of digoxin |
Magnesium (parenteral) |
Profound hypotension reported with nifedipine and intravenous magnesium sulphate in pre-eclampsia |
Phenobarbital |
Effect of nifedipine reduced |
Phenytoin |
Reduced effect of nifedipine |
Propranolol |
Severe hypotension and heart failure occasionally |
Ritonavir |
Plasma concentration increased by ritonavir |
Rifampicin |
Accelerated metabolism of nifedipine (plasma concentration significantly reduced) |
Theophylline |
Enhanced theophylline effect (increased plasma-theophylline concentration) |
Timolol |
Severe hypotension and heart failure occasionally |
NITROUS OXIDE |
|
Chlorpromazine |
Enhanced hypotensive effect |
Fluphenazine |
Enhanced hypotensive effect |
Haloperidol |
Enhanced hypotensive effect |
Methotrexate |
Increased antifolate effect (avoid concomitant use) |
Verapamil |
Enhanced hypotensive effect and AV delay |
NORADRENALINE |
|
Guanethidine + methyldopa + reserpine + tricyclic antidepressants |
Pressor response to norepinephrine may be increased |
Cocaine |
Increased risk of arrhythmias |
MAOIs |
Hypertensive crisis occurs |
Nonselective β-blockers |
Increased hypertensive effects |
OMEPRAZOLE |
|
Cilostazol |
Increased levels of cilastazole |
Nelfinavir |
Decreased level of nelfinavir |
Raltegravir |
Increased levels of raltigavir |
ONDANSETRON |
|
Tramadol |
Decreased effectiveness of tramadol |
OXCARBAMAZEPINE |
|
Lamotrigine |
Decreased levels of lamotrigine |
OXYTETRACYCLINE |
|
Calcium and Iron dextran |
Formation of non-absorbable complexes |
Penicillins |
Antagonism of effect of oxytetracycline |
Etritenate and isotretinoin |
Associated with increased risk of intracranial hypertension |
Oral contraceptives |
May decrease the effect of oral contraceptives |
PHENOBARBITONE |
|
Amitriptyline |
Antagonism of anticonvulsant effect (convulsive threshold lowered); metabolism of amitriptyline accelerated (reduced plasma concentration) |
Carbamazepine |
Enhanced toxicity without corresponding increase in antiepileptic effect; plasma concentration of carbamazepine often lowered |
Cyclosporine |
Metabolism of cyclosporine accelerated (reduced effect) |
Haloperidol |
Antagonism of anticonvulsant effect (convulsive threshold lowered); metabolism of haloperidol accelerated (reduced plasma concentration) |
Nifedipine |
Effect of nifedipine reduced |
Phenytoin |
Enhanced toxicity without corresponding increase in antiepileptic effect; plasma concentration of phenytoin often lowered but may be raised; plasma concentration of phenobarbital often raised |
Valproic acid |
Enhanced toxicity without corresponding increase in antiepileptic effect; plasma concentration of valproic acid often lowered; phenobarbital concentration often raised |
Warfarin |
Metabolism of warfarin accelerated (reduced anticoagulant effect) |
PHENOXYMETHYL PENICILLIN |
|
Methotrexate |
Reduced excretion of methotrexate (increased risk of toxicity) |
PHENYTOIN |
|
Amitriptyline |
Antagonism (convulsive threshold lowered); reduced plasma-amitriptyline concentration |
Carbamazepine |
Enhanced toxicity without corresponding increase in antiepileptic effect; plasma concentration of phenytoin often lowered but may be raised; plasma concentration of carbamazepine often lowered |
Chloramphenicol |
Plasma-phenytoin concentration increased (risk of toxicity) |
Chloroquine |
Convulsive threshold occasionally lowered |
Cyclosporine |
Accelerated metabolism (reduced plasma-cyclosporine concentration) |
Clonazepam |
Enhanced toxicity without corresponding increase in antiepileptic effect; plasma concentration of clonazepam often lowered |
Fluconazole |
Effect of phenytoin enhanced; plasma concentration increased |
Haloperidol |
Antagonism of anticonvulsant effect (convulsive threshold lowered) |
Isoniazid |
Metabolism of phenytoin inhibited (enhanced effect) |
Mefloquine |
Antagonism of anticonvulsant effect |
Metronidazole |
Metabolism of phenytoin inhibited (increased plasma-phenytoin concentration) |
Nifedipine |
Reduced effect of nifedipine |
Pyrimethamine |
Antagonism of anticonvulsant effect; increased antifolate effect |
Rifampicin |
Accelerated metabolism of phenytoin (reduced plasma concentration) |
Sulfadoxine + Pyrimethamine |
Plasma-phenytoin concentration increased; increased antifolate effect |
Sulfamethoxazole + Trimethoprim |
Antifolate effect and plasma-phenytoin concentration increased |
Valproic acid |
Enhanced toxicity without corresponding increase in antiepileptic effect; plasma concentration of valproic acid often lowered; plasma concentration of phenytoin often raised (but may also be lowered) |
Warfarin |
Accelerated metabolism of warfarin (reduced anticoagulant effect, but enhancement also reported) |
PIOGLITAZONE |
|
NSAID |
Increased risk of fluid retention |
Rifampicin |
Decreased plasma concentration. |
Ketoconazole |
Increased plasma concentration. |
PIPERACILLIN + TAZOBACTAM |
|
Aminoglycosides |
Inactivation of aminoglycosides |
Methotrexate |
Reduced clearance of methotrexate |
PREDNISOLONE |
|
Amphotericin B |
Increased risk of hypokalaemia (avoid concomitant use unless prednisolone needed to control reactions) |
Carbamazepine |
Accelerated metabolism of prednisolone (reduced effect) |
Phenobarbital |
Metabolism of prednisolone accelerated (reduced effect) |
Phenytoin |
Metabolism of prednisolone accelerated (reduced effect) |
Rifampicin |
Accelerated metabolism of prednisolone (reduced effect) |
Vaccines, Live |
High doses of prednisolone impair immune response; avoid use of live vaccines |
Warfarin |
Anticoagulant effect altered |
PROPOFOL |
|
Fentanyl |
Concomitant use in paediatric patients may result in serious bradycardia |
CNS depressants |
Increased sedative, anaesthetic and cardiorespiratory effects |
PYRIDOXINE |
|
Levodopa |
Antagonism of levodopa unless carbidopa also given |
PYRIMETHAMINE |
|
Artemether + Lumefantrine |
Avoid concomitant use |
Methotrexate |
Antifolate effect of methotrexate increased |
Phenytoin |
Antagonism of anticonvulsant effect; increased antifolate effect |
Sulfonamides + Trimethoprim |
Increased antifolate effect |
RALOXIFENE |
|
Estrogen |
Increased risk of adverse effects |
RAMIPRIL |
|
Diuretics |
Excessive reduction of blood pressure |
Potassium supplements/Potassium sparing diuretics |
Increased risk of hyperkalemia |
Lithium |
Increased serum lithium levels and lithium toxicity |
RIFAMPICIN |
|
Azathioprine |
Transplants rejected |
Cyclosporine |
Accelerated metabolism (reduced plasma-cyclosporine concentration) |
Dapsone |
Reduced plasma-dapsone concentration |
Fluconazole |
Accelerated metabolism of fluconazole (reduced plasma concentration) |
Glibenclamide |
Accelerated metabolism (reduced effect) of glibenclamide |
Haloperidol |
Accelerated metabolism of haloperidol (reduced plasma-haloperidol concentration) |
Nifedipine |
Accelerated metabolism of nifedipine (plasma concentration significantly reduced) |
Phenytoin |
Accelerated metabolism of phenytoin (reduced plasma concentration) |
Corticosteroids |
Accelerated metabolism of corticosteroids |
Verapamil |
Accelerated metabolism of verapamil (plasma concentration significantly reduced) |
Warfarin |
Accelerated metabolism of warfarin (reduced anticoagulant effect) |
RITONAVIR |
|
Carbamazepine |
Plasma concentration increased by ritonavir |
Cyclosporine |
Plasma concentration increased by ritonavir |
Diazepam |
Plasma concentration increased by ritonavir (risk of extreme sedation and respiratory depression-avoid concomitant use) |
Fluconazole |
Plasma concentration increased by ritonavir |
Verapamil |
Plasma concentration increased by ritonavir |
Warfarin |
Plasma concentration increased by ritonavir |
SALBUTAMOL |
|
Methyldopa |
Acute hypotension reported with salbutamol infusion |
SILDENAFIL |
|
Protease inhibitors |
Sildenafil metabolism is inhibited |
Alpha blockers |
Avoid concomitant use (may lead to low blood pressure) |
Ketoconazole |
Increased action of sildenafil |
Erythromycin |
Increased action of sildenafil |
Verapamil |
Increased action of sildenafil |
Nitrates |
Vasoconstrictor activity of nitrates is potentiated |
STREPTOMYCIN |
|
Amphotericin B |
Increased risk of nephrotoxicity |
Cyclosporine |
Increased risk of nephrotoxicity |
Cisplatin |
Increased risk of nephrotoxicity and ototoxicity |
Furosemide |
Increased risk of ototoxicity |
Neostigmine |
Antagonism of effect of neostigmine |
Suxamethonium |
Enhanced muscle relaxant effect |
STRONTIUM RENELATE |
|
Calcium products |
Reduced biovailability of strontium ranelate. |
Tetracycline |
Reduced absorption of oral tetracycline |
Quinolone antibiotics |
Reduced absorption of quinolone antibiotics |
Almunium and Magnesium Hydroxides |
Decreased absorption of strontium ranelate |
SULFADOXINE + PYRIMETHAMINE |
|
Artemether + Lumefantrine |
Avoid concomitant use |
Cyclosporine |
Increased risk of nephrotoxicity |
Glibenclamide |
Effect of glibenclamide rarely, enhanced |
Methotrexate |
Antifolate effect of methotrexate increased; risk of methotrexate toxicity increased |
Phenytoin |
Plasma-phenytoin concentration increased; increased antifolate effect |
Warfarin |
Enhanced anticoagulant effect |
SULFASALAZINE |
|
Azathioprine |
Increased risk of leukopenia |
Mercaptopurine |
Increased risk of leukopenia |
TACROLIMUS |
|
Aminoglycosides |
Increased risk of renal dysfunction |
Carbamazepine |
Decreased tacrolimus blood concentration |
Cisplatin |
Increased risk of renal dysfunction |
Clarithromycin |
Increased tacrolimus blood concentration |
Chloramphenicol |
Increased tacrolimus blood concentration |
Clotrimazole |
Increased tacrolimus blood concentration |
Phenytoin |
Decreased tacrolimus blood concentration |
Rifampin |
Decreased tacrolimus blood concentration |
Diltiazem |
Increased tacrolimus blood concentration |
Nifedipine |
Increased tacrolimus blood concentration |
Verapamil |
Increased tacrolimus blood concentration |
TELMISARTAN |
|
Lithium |
Increased in serum lithium concentration and toxicity |
THALIDOMIDE |
|
Barbiturates |
Enhanced sedative activity |
Alcohol |
Enhanced sedative activity |
Chlorpromazine |
Enhanced sedative activity |
Reserpine |
Enhanced sedative activity |
Vincristine |
Potential to cause peripheral neuropathy |
Bortezomib |
Potential to cause peripheral neuropathy |
THEOPHYLLINE |
|
Ciprofloxacin |
Increased plasma-theophylline concentration; increased risk of convulsions |
Erythromycin |
Inhibition of theophylline metabolism (increased plasma-theophylline concentration resulting in theophylline toxicity) |
Fluconazole |
Plasma-theophylline concentration increased |
TIMOLOL |
|
Epinephrine |
Severe hypertension |
Verapamil |
Asystole, severe hypotension and heart failure |
Note: Systemic absorption may follow topical application of timolol to the eye |
|
TOPIRAMATE |
|
Carbamazepine |
Reduced plasma level of topiramate |
Phenytoin |
Reduced plasma level of topiramate |
Rifampin |
Reduced plasma level of topiramate |
TRANEXAMIC ACID |
|
Clotting factor complexes |
Increased risk of thrombotic complications |
Hormonal contraception |
Exacerbate the increased thrombotic risk associated with combination hormonal contraceptives |
all-trans Retinoic acid |
Concomitant use in women with acute promyelocytic leukemia taking all-trans retinoic acid for remission induction may cause exacerbation of the procoagulant effect of all-trans retinoic acid |
TRIMETHOPRIM |
|
Mercaptopurine |
Increased risk of haematological toxicity |
Methotrexate |
Antifolate effect of methotrexate increased (avoid concomitant use) |
Phenytoin |
Antifolate effect and plasma-phenytoin concentration increased |
Pyrimethamine |
Increased antifolate effect |
Sulfadoxine + Pyrimethamine |
Increased antifolate effect |
VALPROIC ACID |
|
Carbamazepine |
Enhanced toxicity without corresponding increase in antiepileptic effect; plasma concentration of valproic acid often lowered; plasma concentration of active metabolite of carbamazepine often raised |
Chloroquine |
Convulsive threshold occasionally lowered |
Mefloquine |
Antagonism of anticonvulsant effect |
Phenobarbital |
Enhanced toxicity without corresponding increase in antiepileptic effect; plasma concentration of valproic acid often lowered; phenobarbital concentration often raised |
Phenytoin |
Enhanced toxicity without corresponding increase in antiepileptic effect; plasma concentration of valproic acid often lowered; plasma concentration of phenytoin often raised (but may also be lowered) |
VANCOMYCIN |
|
Cyclosporine |
Increased risk of nephrotoxicity |
Furosemide |
Increased risk of ototoxicity |
VARICELLA VACCINE |
|
Salicylates |
Increased risk of Reye’s syndrome |
VERAPAMIL |
|
Atenolol |
Asystole, severe hypotension and heart failure |
Carbamazepine |
Enhanced effect of carbamazepine |
Digoxin |
Increased plasma concentration of digoxin; increased AV block and bradycardia |
Halothane |
Enhanced hypotensive effect and AV delay |
Ketamine |
Enhanced hypotensive effect and AV delay |
Lidocaine |
Increased risk of myocardial depression |
Rifampicin |
Accelerated metabolism of verapamil (plasma concentration significantly reduced) |
VINBLASTINE |
|
Bleomycin |
Increased risk of cardiovascular toxicity |
WARFARIN |
|
Acetylsalicylic acid |
Increased risk of bleeding due to antiplatelet effect |
Azathioprine |
Anticoagulant effect reduced |
Azithromycin |
Enhanced anticoagulant effect of warfarin |
Carbamazepine |
Accelerated metabolism of warfarin (reduced anticoagulant effect) |
Ceftazidime |
Enhanced anticoagulant effect |
Ceftriaxone |
Enhanced anticoagulant effect |
Chloramphenicol |
Enhanced anticoagulant effect |
Ciprofloxacin |
Enhanced anticoagulant effect |
Corticosteroids |
Anticoagulant effect altered |
Doxycycline |
Anticoagulant effect enhanced |
Erythromycin |
Enhanced anticoagulant effect |
Fluconazole |
Enhanced anticoagulant effect |
5-Fluorouracil |
Anticoagulant effect enhanced |
Glibenclamide |
Enhanced hypoglycaemic effects and changes to anticoagulant effect |
Griseofulvin |
Metabolism of warfarin accelerated (reduced anticoagulant effect) |
Ibuprofen |
Anticoagulant effect enhanced |
Levamisole |
Anticoagulant effect enhanced |
Levonorgestrel |
Antagonism of anticoagulant effect |
Levothyroxine |
Enhanced anticoagulant effect |
Medroxyprogesterone |
Antagonism of anticoagulant effect |
Mercaptopurine |
Anticoagulant effect reduced |
Metronidazole |
Enhanced anticoagulant effect |
Nalidixic acid |
Enhanced anticoagulant effect |
Norethisterone |
Antagonism of anticoagulant effect |
Ofloxacin |
Enhanced anticoagulant effect |
Phenobarbital |
Metabolism of warfarin accelerated (reduced anticoagulant effect) |
Phenytoin |
Accelerated metabolism of warfarin (reduced anticoagulant effect, but enhancement also reported) |
Phytomenadione |
Antagonism of anticoagulant effect by phytomenadione |
Proguanil |
Isolated reports of enhanced anticoagulant effect |
Quinidine |
Anticoagulant effect may be enhanced |
Rifampicin |
Accelerated metabolism of warfarin (reduced anticoagulant effect) |
Ritonavir |
Plasma concentration increased by ritonavir |
Sulfadiazine |
Enhanced anticoagulant effect |
Sulfadoxine + Pyrimethamine |
Enhanced anticoagulant effect |
Sulfamethoxazole + Trimethoprim |
Enhanced anticoagulant effect |
Tamoxifen |
Enhanced anticoagulant effect |
ZIDOVUDINE |
|
Fluconazole |
Increased plasma concentration of zidovudine (increased risk of toxicity) |
Stavudine |
May inhibit effect of stavudine (avoid concomitant use) |
ZOLPIDEM |
|
Rifampin |
Pharmacodynamic effects of zolpidem are decreased |
Ketoconazole |
Pharmacodynamic effects of zolpidem are increased |