One factor having great influence on the success of drug therapy is patient adherence to the prescribed dosage schedule. In a review of patient compliance studies, Stewart and Cluff found that 25% to 59% of patients with various diagnoses failed to take drugs as prescribed. l Ayd reported that 60% of chronic medical and psychiatric outpatients instructed to take a single drug three times daily omitted between 25% and 50% of the prescribed doses.2 Patient compliance to dosage schedules declined further as the number of drugs prescribed increased. When Willcox et al. studied chlorpromazine and imipramine in 125 psychiatric outpatients, approximately half of the study group departed from the prescribed regimen. 3 Depressed patients were found to be considerably less reliable than those with other psychiatric disorders. In a series of crossover studies designed to compare patient adherence to single and divided doses of fluphenazine, 15 physician-members of the General Practitioner Research Group reported that patients were more likely to deviate from multiple dose treatment programs than from single dose schedules:l The Ayd survey further revealed that many psychiatric patients are typically treated with a variety of drugs including neuroleptics, antidepressants, antiparkinson agents, minor tranquilizers, and hypnotics.2 Also, many such patients may receive medication for other co-existing physical illnesses. Based on these and other studies,5.6 efforts to decrease the number and dosage frequency of drugs to be taken by psychiatric patients might be expected to result in greater patient compliance to the prescribed dosage schedule. Psychotropic drugs such as imipramine, chorpromazine, and haloperidol are commonly prescribed in divided doses. However, their relatively long biological half-life, slow rate of metabolism and excretion, and somewhat delayed pharmacological effects also make them potentially useful for single-dose administration.7 Imipramine pamoate, a new salt of a proven antidepressant, imipramine hydrochloride, has recently been investigated for efficacy and safety following