Rimantadine Cimetidine

Drugs that may affect rimantadine include acetaminophen, aspirin, and cimetidine. 

Rimantadine (Flumadine) [Antiviral] Uses Prophylaxis Rx of influenza A viral Infxns but not for HlNl swine flu Action Antiviral Dose Adults Feds >9 y. 100 mg PO bid Feds 2-9 y. 5 mg/kg/d PO, 150 mg/d max daily w/ severe renal/hepatic impair elderly initiate w/in 48 h of Sx onset Caution [C, -] w/ cimetidine avoid w/ PRG, breast-feeding Contra Component amantadine allergy Disp Tabs SE Orthostatic X BP, edema, dizziness, GI upset, X Sz threshold Interactions T Effects W/ cimetidine i effects W/ acetaminophen, ASA EMS Concurrent EtOH usage may result in light-headedness, confusion, syncope, and hypotension OD May cause N/V, tremors, Szs, anticholinergic Sxs, ventricular arrhythmias give IV fluids... 

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. 

Following oral administration, rimantadine is extensively metabolized in the liver, with <25% of the dose excreted in the urine as unchanged drug. Three hydroxy-lated metabolites have been found in plasma. These metabolites, an additional conjugated metabolite, and parent drug account for 74% of a single 200 mg dose excreted in urine over 72 hours. Acetaminophen and aspirin reduce, whereas cimetidine increases, the plasma level of rimantadine. 

Cimetidine causes a small but probably clinically unimportant rise in the plasma levels of rimantadine. 

In 23 healthy subjects the AUC of a single 100-mg dose of rimantadine was increased by 20% and the apparent total clearance reduced by 18% when it was taken one hour after the first dose of cimetidine 300 mg four times daily for 6 days. The authors of the study suggest that these changes are likely to have little, if any, clinical consequences. The effects of multiple dose concurrent use are not known. 

Holazo AA, Choma N, Brown S Y, Lee LF, Wills RJ. Effect of cimetidine on the disposition of rimantadine inheallhy subjects. AnUmicrob Agents Chemo r( 9 ) 33 820-3. 

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