Patterns of plasma imipramine-desipramine concentrations in patients receiving concomitant fluphenazine decanoate.

Plasma levels of imipramine and desipramine were monitored in a series of 13 patients with postpsychotic depressions who had a fixed dose of imipramine (150 mg/day) added to their clinically adjusted, stable dose of fluphenazine decanoate. Despite the potential for metabolic inhibition of the tricyclic drug by the neuroleptic drug, no relationship was found between the fluphenazine dose and the subsequent plasma concentrations of imipramine and desipramine. However, plasma antidepressant levels after 1 week at a low dose (50 mg/day) identified patients who later generated high plasma antidepressant levels at the full antidepressant dosage. The clinical implications of these observations are discussed.