PHARMACOKINETICS OF STANDARD (LITHICARB) AND SUSTAINED-RELEASE (PRIADEL) LITHIUM-CARBONATE PREPARATIONS IN PATIENTS

Equivalent oral dosages (800 mg, 21.6 mmol) of a standard (Lithicarb) and a sustained-release (Priadel) Li2CO3 preparation were administered to 6 patients receiving Li maintenance treatment using a randomized cross-over design. There were no significant differences in the 2 preparations for 24 h plasma level curves, 24 h bioavailability, peak plasma concentrations (Cmax), time to peak plasma concentrations (Tmax) or urinary excretion rates. These results are in agreement with a previous study using Priadel in healthy volunteers, and indicate that Priadel is a delayed-release, rather than a true sustained-release preparation. To maintain therapeutic plasma levels and to minimize adverse effects that may occur with high plasma Li levels, Priadel needs to be administered in divided dosages rather than as a single daily dose.