Cimetidine drug interactions

Cimetidine Drug Interactions (Decreased Hepatic Metabolism)... 

Bauer LA, Black D, Gensler A. Procainamide-cimetidine drug interaction in elderly male patients. J Am Geriatr Soc 1990 38(4) 467-9. 

Smith SR, Kendall MJ, Lobo J, Beerahee A, Jack DB, Wilkins MR. Ranitidine and cimetidine drug interactions with single dose and steady-state nifedipine administration. Br J Chn Pharmacol 1987 23(3) 311-15. 

Assess for potential drug interactions whenever there is a change in the patient s medications, particularly for patients taking cimetidine, omeprazole, or sucralfate. 

Assess the potential for drug interactions, particularly in patients taking regimens containing metronidazole, clarithromycin, and/or cimetidine. 

Caution is needed to avoid potential drug interactions. Tamsulosin decreases metabolism of cimetidine and diltiazem. Carbamazepine and phenytoin increase catabolism of a-adrenergic antagonists. 

Drugs that may affect amiodarone include hydantoins, cholestyramine, fluoroquinolones, rifamycins, ritonavir, and cimetidine. Drugs that may be affected by amiodarone include anticoagulants, beta-blockers, calcium channel blockers, cyclosporine, dextromethorphan, digoxin, disopyramide, fentanyl, flecainide, hydantoins, lidocaine, methotrexate, procainamide, quinidine, and theophylline. Drug/Lab test interactions Amiodarone alters the results of thyroid function tests, causing an increase in serum T4 and serum reverse T3 levels and a decline in... 

Concomitant cimetidine- Give an initial dose of 5 mg to patients concomitantly taking cimetidine (see Drug Interactions). 

Because trimetrexate is metabolized by a P450 enzyme system, drugs that induce or inhibit this drug metabolizing enzyme system may elicit important drug interactions that may alter trimetrexate plasma concentrations, which include erythromycin, rifampin, rifabutin, ketoconazole, fluconazole, cimetidine, nitrogen substituted imidazole drugs (eg, clotrimazole, ketoconazole, miconazole). 

As it inhibits microsomal cytochrome P450 cimetidine has a high potential for drug interactions not shared by the other H2 receptor antagonists. The oxidative metabolism of agents such as anticoagulants, most antiepileptics, some beta-blockers, warfarin, theophylline and many hypnotics, neuroleptics and antidepressants may be reduced, leading to increased effects. 

Several drug interactions involving amantadine and rimantadine are clinically significant. Anticholinergic drugs can potentiate the toxicity of amantadine. Thiazide-triamterene, trimethoprim-sulfamethoxazole, quinine, and quinidine increase plasma amantadine levels. Cimetidine decreases rimantadine clearance, and aspirin and acetaminophen decrease rimantadine plasma levels. 

Eto, K., Y. Gomita, K. Furuno, K. Yao, M. Moriyama, and Y. Araki. Influences of cigarette smoke inhalation on pharmacokinetics of cimetidine in rats. DrugMetab Drug Interact 1991 9(2) 103-114. 

Clinicians should be aware of a few drug interactions with Zolpidem. Flumazenil acts as an antagonist to the hypnotic effects of zolpidem. There is decreased alertness when zolpidem is combined with cimetidine. There is an increase in anterograde amnesia in volunteers treated with a combination of imipramine and zolpidem. Haloperidol, ranitidine, chlorpromazine, warfarin, and digoxin, along with cimetidine and flumazenil, do not alter the pharmacokinetics of zolpidem (Salva and Costa, 1995). 

Drug Interactions Other antihypertensive agents Carbamazepine (vasodilators, ACE inhibitors, Rifampin diuretics, and beta-blockers) Phenobarbital Digoxin Cyclosporine Disopyramide Theophylline Flecainide Inhalation anesthetics Quinidine Neuromuscular blocking agents Cimetidine Lithium ... 

Drug Interactions Cyclosporine Gemfibrozil Niacin Erythromycin Cholestyramine/Colestipol Warfarin Cimetidine Digoxin ... 

Drug Interactions Gemfibrozil Niacin Erythromycin Cholestyramine Digoxin Cimetidine/ranitidine/ omeprazole Rifampicin Warfarin Itraconazole Gemfibrozil Niacin Erythromycin Propranolol Digoxin Warfarin Antacids Colestipol Digoxin Erythromycin Oral contraceptives Fibrates Niacin Azole antifungals... 

Hatorp V, Thomsen MS. Drug interaction studies with repaglinide repaglinide on digoxin or theophylline pharmacokinetics and cimetidine on repaglinide pharmacokinetics. J Clin Pharmacol 2000 40(2) 184-92. 

Potential drug interactions include an increased AUC of zalcitabine when administered in combination with probenecid or cimetidine and decreased bioavailability when zalcitabine is coadministered with antacids or metoclopramide. Lamivudine inhibits the phosphorylation of zalcitabine in vitro, potentially interfering with its efficacy. 

Problems of combining cimetidine with hypertension drugs were soon apparent. In 1981, ranitidine (Zantac, 8.91), another H2-receptor antagonist, reached the market. Ranitidine also inhibits metabolism, but only CYP2D6. Isoform 2D6 is less crucial in the metabolism of common drugs. Ranitidine took much market share from cimetidine because of cimetidine s relatively large number of drug interactions. 

Drug interactions include rise in plasma concentration when concomittant administration with cimetidine and lowering of the concentration with barbiturates, phenytoin, rifampin. Digoxin levels may be variably affected, can rise. 

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