Phenytoin (Dilantin) for Bipolar Disorder

Although phenytoin has been used as a seizure medication for decades, it has never been studied for Bipolar Disorder until very recent, small double-blind studies covered below.  While these successful double-blind studies aren't a lot, its more than exists for gabapentin, topiramate, tiagabine, zonisamide, and levetiracetam combined.  It's also inexpensive.

Phenytoin Appears Mood Stabilizer for Both Mania and Depression in Small Studies: In a 5-week DB PC study of 39 manic patients of haloperidol+phenytoin vs. haloperidol+placebo, significantly more improvement occurred with phenytoin. In another DB crossover 6-month each study of 23 stable bipolar patients who had at least one episode per year in the previous 2 yr despite ongoing prophylaxis, 3 patients relapses on phenytoin and 9 on placebo [p =0.02]. In a 6-week DB study of phenytoin vs. fluoxetine in 33 patients with unipolar depression, there was no difference between fluoxetine and phenytoin. Phenytoin: an anti-bipolar anticonvulsant? Bersudsky Y. Ben Gurion University, Israel. Int J Neuropsychopharmacol. 2005 Oct 5;:1-6

Phenytoin Helped Prevent Relapse in Small DB: 23 bipolar patients with at least one relapse in each of the previous two years had phenytoin added to regular meds during a period of stability in a DB PC crossover study with each patient receiving phenytoin and placebo for 6 months each.  There were 3 relapses on phenytoin and 9 on placebo (p=.02). Ben Gurion Univ.  Prophylactic effect of phenytoin in bipolar disorder: a controlled study. Mishory A, Winokur M, Bersudsky Y. Bipolar Disord. 2003 Dec;5(6):464-7.