Effect of intravenous infusion of amitriptyline on total blood serotonin content

18 female patients with primary depression received a slow intravenous infusion of amitriptyline and a good therapeutic response was observed in 15 patients as early as after 6 days. A highly significant correlation was found between improvement scores following the first and last infusions, which suggests that intravenous infusion of amitriptyline may serve as a prognostic test for prediction of drug efficacy. Total blood serotonin content prior to treatment was significantly lower than in normal controls. Amitriptyline infusion caused variable changes in blood serotonin and the changes were inversely correlated with pretreatment levels. A series of six infusions caused a gradual increase in baseline levels, together with a rapid decrease in the magnitude of the amitriptyline-induced changes in serotonin content.