Introduction. The aim of the study was to assess the efficacy of single ketamine infusion in patients with bipolar depression, receiving mood-stabilizing drugs, previously treated with antidepressant drugs, which was inefficient in the context of vitamin B12 level before the procedure application.
Methodology. Twenty eight patients suffering from bipolar depression were included in the study: 5 males and 23 females, aged 27–67 years (mean 46), receiving ≥1 mood-stabilizing drugs of the first or/and second generation. The infusion of ketamine 0.5 mg/kg was performed after ≥7 days of discontinuation of antidepressant drugs. The criterion for a clinical improvement was the ≥50% reduction on the 17-item Hamilton Depression Rating Scale on the 7th day after infusion as compared to the pre-infusion status. The patients were divided into three groups: 1) vitamin B12 level < 350 pg/ml (11 patients); 2) vitamin B12 level ≥350 pg/ml (10 patients); 3) vitamin B12 level < 350 pg/ml, injected with 1000 μg before the infusion.
Results. The mean level of improvement in these groups after 7 days of treatment equalled 28%, 55% and 71%, respectively. Compared with the group 1, the improvement was significantly higher in group 2 (p = 0.011) and 3 (p = 0.003). A significant correlation was found between baseline vitamin B12 level (taking into account the supplementation in 7 patients) and clinical efficacy (r = 0.51; p = 0.006).
Conclusions. The results obtained suggest that high vitamin B12 level prior to ketamine infusion is associated with a better clinical efficacy. In patients with low vitamin B12 level, a supplementation with this vitamin may be recommended for achieving optimal effects.