Figure 2.

Therapeutic serum levels of lithium and valproate did not correlate with ketamine's antidepressant efficacy. Treatment-resistant patients with bipolar disorder (BD) currently experiencing a major depressive episode were maintained on therapeutic but subeffective serum levels of lithium or valproate for at least four weeks. Mean same-day pre-ketamine lithium (n = 22) and valproate (n = 12) levels were 0.79 ± 0.15 mEq/L and 79.6 ± 12.4 mg/mL, respectively. These levels correlated with ketamine's antidepressant efficacy at three time points: 230 minutes (same-day/hyperacute), day one (next-day/acute), and day seven (sustained) after ketamine infusion. Serum lithium levels did not correlate with ketamine's antidepressant efficacy at these three time points (a). Serum valproate levels positively correlated with ketamine's antidepressant efficacy at 230 minutes after infusion, r = 0.59, p = 0.04, but this did not survive adjustment for multiple comparisons (p _adjusted = 0.12) (b).