Reactions 514 - 13 Aug 1994

Imipramine

Myoclonus: case reportSevere myoclonus developed in a 21-year-old woman

during imipramine therapy for psychotic bipolar depression.Three or 4 days after her imipramine dose was increased

from 150mg to 200mg at bedtime the woman was admittedwith suicidal thoughts. She had a relapse of depression andevidence of imipramine adverse effects, despite a modestserum imipramine level. She also had generalised myoclonusboth upon action and at rest.

Depression persisted, along with delusions of guilt andpsychomotor retardation. The woman then developeddystonia after haloperidol was started; this responded to IVdiphenhydramine. Benztropine was also started. However,she developed catatonia which, along with most moodsymptoms, responded completely to IM lorazepam. Herdepressive symptoms later returned.

Approximately 9 days after the imipramine dose increase,mild urinary retention developed and myoclonus hadincreased in severity to 10cm amplitude involuntarymovements of all extremities every 2–3 seconds. The woman’simipramine dosage was decreased to 150 mg at bedtime andlithium was started. Her psychiatric symptoms rapidlyimproved. Further investigations revealed left-sidedschizencephaly and a corresponding history of milddevelopmental delay.

Haloperidol and benztropine were later discontinued.Myoclonus improved, but was still noted 10 days after theimipramine dosage reduction. Several weeks later, imipraminewas replaced by desipramine 150mg at bedtime to minimiseadverse effects. Within 1 month no definite myoclonus couldbe seen.

Author comment: Consultant neurologists considered thatthe myoclonus was almost certainly caused by imipramine.‘Mild myoclonus is reasonably common with various cyclicantidepressants. However, very severe myoclonus induced byan antidepressant is rare.’Black KJ, et al. Severe imipramine-induced myoclonus in a patient with psychoticbipolar depression, catatonia, and schizencephaly. Annals of Clinical Psychiatry 6:45-49, Mar 1994 - USA 800285124

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Reactions 13 Aug 1994 No. 5140114-9954/10/0514-0001/$14.95 Adis © 2010 Springer International Publishing AG. All rights reserved