Prophylactic effect of phenytoin in bipolar disorder: a controlled study
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Updated: Jul 1, 2026

Pupillary Response as Assessment of Effective Seizure Induction by Electroconvulsive Therapy
Published on: April 11, 2019
A Mishory1, M Winokur, Y Bersudsky
1Barzilai Hospital, Ashkelon Faculty of Health Sciences, Ministry of Health, Mental Health Center, Ben Gurion University of the Negev, Beersheva, Israel.
Objective:
Phenytoin is an effective anticonvulsant that has not previously been studied prophylactically in bipolar (BP) patients. Thus a study of phenytoin prophylaxis was undertaken and is herein reported.
Method:
Bipolar patients were studied who had at least one episode per year in the previous 2 years despite ongoing prophylaxis. Patients were stable for a mean of 4 months (range 1-13) before entering the study. Phenytoin or placebo was added to their current therapy in a double-blind cross-over design for 6 months in each phase. Thirty observation periods of 6 months each were studied for 23 patients.
Results:
Three patients had relapse on phenytoin and nine had relapse on placebo. There was a significant prophylactic effect of phenytoin in BP disorder [Cox's F-test for comparing survival in two groups: F(6, 18) = 3.44, p = 0.02].
Conclusions:
This study suggests prophylactic effects of add-on phenytoin in BP illness. However, the number of patients was small and confirmation is necessary.
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