Investigation of the orthostatic reaction after intravenous administration of imipramine,chlorimipramine, and imipramine-N-oxide

Three age- and sex-matched groups of 10 patients were treated intravenously with imipramine, chlorimipramine, and imipramine-N-oxide, respectively, in increasing doses from 25 mg to 150–175 mg given as single daily infusions during 1 hour. No systemic changes of heart frequency and blood pressure were found during the infusions in spite of the high dosage of tricyclic antidepressants given in such a short period as 1 hour. The patients were examined regarding orthostatic reactions as well as ECG changes before, after 4–5 infusions and after 8–10 infusions. There were more orthostatic abnormalities and ECG changes in the patients treated with imipramine than in those treated with imipramine-N-oxide and there were practically no changes in the chlorimipramine group. However, no statistically significant orthostatic changes were found.