Dimetacrine is a useful antidepressant which can be used for the treatment of various types of depression. Dimetacrine in the highest concentration, 10 μM, decreases the contractile force to 36.5±9.1%. Dimetacrine, 0.3 μM, causes no statistically significant decline in contractile force from the controls. Tachycardia is observed after the administration of Dimetacrine, 1 to 3 mg/kg i.v., and the maximum response is obtained in dose of 3 mg/kg i.v.. The administration of Dimetacrine, 30 mg/kg i.v., causes an abrupt fall in blood pressure with tachycardia or bradycardia followed by cardiac arrest. Respiratory rate increases 40 min after the onset of infusion of Dimetacrine. Arterial blood pressure falls 50 min after the onset of infusion of Dimetacrine.