Twelve-hour brain lithium concentration in lithium maintenance treatment of manic-depressive disorder: daily versus alternate-day dosing schedule

Abstract

The 12-h brain lithium concentration was measured by lithium-7 magnetic resonance spectroscopy in ten manic-depressive patients receiving daily or alternate-day lithium carbonate treatment. The median dose of lithium carbonate was 800 mg in the daily treatment group and 1200 mg in the alternate-day group. Median 12-h serum lithium concentration in the two groups was 0.86 mmoll⁻¹ and 0.55 mmoll⁻¹, respectively, while the corresponding concentration in brain was 0.67 mmoll⁻¹ and 0.52 mmoll⁻¹, respectively. The 12-h brain lithium concentration was independent of lithium dosing schedule (multiple linear regression), but correlated significantly with the 12-h serum lithium concentration (P=0.003; B=0.53, 95% c.l. 0.24–0.82; β=0.83). Thus at identical 12-h serum lithium concentrations the 12-h brain lithium concentration is similar with both treatment regimes. As the risk of manic-depressive relapse during alternate-day lithium treatment is in our experience 3-fold greater than with daily treatment (at similar mean 12-h serum lithium concentration), the findings suggest that the difference in the prophylactic efficacy of the two dosing schedules is unrelated to differences in the 12-h brain lithium concentration.