Quinidine Amantadine

Amantadine is used cautiously in patients with seizure disorders, psychiatric problems, renal impairment, and cardiac disease. Amantadine is a Pregnancy Category B drug and is used cautiously during pregnancy and lactation. Concurrent use of antihistamines, phenothiazines, tricyclic antidepressants, disopyramide, and quinidine may increase the anticholinergic effects (dry mouth, blurred vision, constipation) of amantadine... 

Amantadine, amiodarone, barbiturates, benzodiazepines, carbamazepine, chlorpromazine, fluoroquinolones, furosemide, NSAIDs, promethazine, psoralens, quinidine, simvastatin, sulfonamide antimicrobials, sulfonylureas, tetracyclines, and thiazides... 

Drugs that may affect triamterene include ACE inhibitors, cimetidine, and indomethacin. Drugs that may be affected by triamterene include amantadine and potassium preparations. Triamterene will interfere with the fluorescent measurement of quinidine serum levels. 

Drugs that may affect amantadine include anticholinergic drugs, triamterene and thiazide diuretics, quinidine, quinine, and trimethoprim/sulfamethoxazole. 

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. 

Memantine is not a major substrate for hepatic cytochrome P450 isoenzymes and has not been shown to significantly inhibit or induce these enzymes. However, memantine is partially excreted by renal tubular secretion. Thus, concomitant use of other medications that use the same renal system (i.e., triampterene, hydrochlorothiazide, digoxin, cimetidine, ranitidine, metformin, and quinidine) may affect plasma levels of both drugs (Namenda 2005). Memantine should not be used in combination with other NMDA receptor antagonists, such as amantadine or dextromethorphan, because these combinations have not been formally studied. The clearance of memantine can be reduced when the urine is alkalinized, such as with the concomitant use of sodium bicarbonate or carbonic anhy-... 

In a single-dose study, quinidine and quinine modestly reduced the loss of amantadine in the urine in men, but not women. However, the absence of any clinical reports suggest that a significant interaction is unlikely. 

Single-dose studies into the renal exeretion of amantadine in healthy sub-jeets found that quinine sulfate 200 mg and quinidine sulfate 200 mg re-dueed the renal clearance of oral amantadine 3 mg/kg by about 30%, but only in male subjects. Whether long-term use of these drugs would therefore eause a clinically relevant rise in serum amantadine levels is uncertain. However, the absenee of any elinieal reports suggests it is unlikely. 

Gaudry SE, Sitar DS, Smyth DD, McKenzie JK, Aoki FY. Gender and age as factws in the inhibition of renal clearance of amantadine by quinine and quinidine. Clin Pharmacol Ther (1993) 54,23-7. 

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