Amantadine-dyazide interaction.

To document an interaction between amantadine hydrochloride and Dyazide that had apparently produced amantadine toxicity, a patient was given amantadine alone for 1 week, followed by amantadine plus Dyazide for another week, under controlled conditions. A diuretic effect was observed after Dyazide was added to the regimen, but the urine amantadine excretion fell, and the drug's plasma concentration increased. It was concluded that one or both of the components of Dyazide (hydrochlorothiazide and triamterene) reduce the clearance of amantadine and can produce higher plasma concentrations and toxic effects.