- Lithium augmentation of antidepressant effects in patients unimproved on antidepressants is well documented. We hypothesized that phenytoin, reported to have antimanic, antidepressant and prophylactic effects on affective disorder, might also augment in SSRI failures. Twenty five patients were recruited and twenty had data sufficient for analysis between phenytoin and placebo in depression ratings. No effect was found. This study was a small study. Lithium's ability to augment in antidepressant failures may not be shared with the anticonvulsant mood stabilizers.