Ketamine dosing formula in treatment-resistant bipolar depression.

Background: Intravenous ketamine is effective in treatment-resistant bipolar depression (TRBD) with dosing typically based on actual body weight (ABW). Objective: This study examined whether alternative normalization formulas are associated with treatment response. Design: A retrospective exploratory analysis of a naturalistic registry for short-term ketamine use. Methods: A total of 22 TRBD inpatients received short-term intravenous ketamine. Doses were recalculated using the Boer and Devine formulas for lean body mass (LBM) and ideal body weight (IBW), and the Mosteller formula for body surface area (BSA). Calculated doses were compared with ABW dosing in responders and nonresponders. Results: Using the Mosteller formula, BSA-normalized doses ranged from 17.63-23.09 mg/m2 in nonresponders and 15.73-23.89 mg/m2 in responders. LBM- and IBW-based recalculations at 0.5 mg/kg yielded lower relative doses, particularly among nonresponders, suggesting potential underdosing. Conclusion: These preliminary findings do not support alternative dosing formulas over ABW, but replication in larger controlled studies is warranted.