Evaluation of a slow-release lithium carbonate formulation.

A slow-release lithium preparation was compared with a standard formulation in normal volunteers and in patients. Pharmacokinetic parameters of normal volunteers were examined after a single dose of each form and the steady-state levels after a b.i.d. dose of the slow-release form. These initial single-dose data suggested that the two formulations are not bioequivalent. However, the area under the curve of the two forms was similar, and the essentially complete recovery of lithium from urine in steady state indicates equal bioavailability. The patients' steady-state levels for the two formulations essentially confirmed the normal subjects' data: with the slow-release form plasma lithium levels were slightly higher, and the postdose lithium level variability was decreased by as much as 50%.