Cimetidine interaction with amitriptyline

The interaction of cimetidine with amitriptyline was assessed by means of amitriptyline and nortriptyline plasma concentration measurements, standing blood pressure and pulse rate, digit symbol substitution, and visual analogue scales. Cimetidine increased plasma amitriptyline concentrations and decreased plasma nortriptyline concentrations, apparently by inhibiting presystemic metabolism. The changes in blood pressure, pulse rate and digit symbol substitution correlated with changes in concentrations of amitriptyline in plasma and expected changes based on a dose ranging preliminary experiment. Changes in subjective ratings of effects correlated with changes in nortriptyline concentrations in plasma.