n. a conventional antipsychotic of the piperidine phenothiazine class. Mesoridazine is a low-potency agent that is a metabolic product of thioridazine. Like the latter drug, its use is associated with life-threatening disturbances in heart rhythm (prolongation of the Q-T interval potentially leading to torsades de pointes syndrome; see electrocardiographic effect). It should not be administered to individuals taking other drugs that prolong the Q-T interval or who have a history of heart rhythm disturbances, and it is appropriate for the treatment of schizophrenia only in individuals who have not responded to other antipsychotic agents. U.S. trade name: Serentil.