Imipramine/bupropion* Inappropriate secretion of antidiuretic hormone: first report

A 78-year-old woman with a history of mild congestive heart failure, adult onset diabetes mellitus and mild hypertension was admitted for a major episode of depression. Medications at the time of admission were imipramine 50 mg/day and digoxin 0.25 mg/day. Physical and laboratory examinations were normal except for serum sodium of 130 mEq/L. This hyponatraemia cleared durinQ a 9-day imiprmaine-free interval. The patient was then entered into a double-blind study for treatment with a new antidepressant bupropion (0-300 mg(day) followed by imipramine. Her other medications were digoxin 0.25 mg/day and occasional lorazepam for anxiety. During bupropion therapy the serum sodium fell from 136 to 128 mEq/L. Bupropion was discontinued and 5 days later imipramine 100-150 mg/day was begun. Hyponatraemia persisted despite fluid restriction to 600 mJjday. The serum sodium increased to 132 mEqjL with an increase in dietary sodium from 2-4 gjday. Ten days after imipramine was discontinued serum sodium increased to 135 mEqjL. the highest level since antidepressant medications were initiated. A diagnosis of antidepressant­Induced inappropriate secretion of anti­diuretic hormone was established, based on the following criteria: hyponatraemia with continued excretion of sodium into the urine; low serum osmolality; an increased urine osmolality: the absence of water intoxication; dehydration or acute cardiac, rena!, hepatic or endocrine abnormalities and correction of electrolyte abnormalities by fluid restriction. Rechallenge with imipramine 100-125 mg/day was accompanied by a decrease in serum sodium from 134 to 127 mEqfl within 7 days. The patient's depression was eventually treated with electroconvulsive therapy. This appears to be the first report 01 inappropriate secretion of antidiuretic hormone associated with imipramine and bupropion. LlSktn. B. el a/. Journal of Clinical Psychopharmacology 4· 146 (Jun 1984)

8 Reactions 25 Aug 1984 0157-7271/84/0825-0008/0$01.00/0 © ADIS Press