Ketamine-induced affective switch in a patient with treatment-resistant depression.

There is growing evidence to support the rapid, albeit short-lived antidepressant effect of subanesthetic dose of ketamine, a noncompetitive glutamate N-methyl-D-aspartate receptor antagonist in treatment-resistant unipolar and bipolar depression. Ketamine is known to cause transient mood elevation or euphoria, psychotomimetic effects, and dissociative symptoms, but its use in unipolar or bipolar depression has not been reported to induce an affective switch amounting to persistent or prolonged hypomania/mania or manic-like syndrome. We report the case of a 52-year-old male with first episode, continuous, nonpsychotic, treatment-resistant, unipolar major depression of 10 years duration, who manifested a switch from depression to mania while being treated with subanesthetic dose of ketamine, given intramuscularly. This case suggests that polarity switch should be considered as a potential side effect while using ketamine for treatment-resistant depression.