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) lithium carbonate preparation were administered to six patients receiving lithium maintenance treatment using a randomized cross-over design. There were no significant differences in the two preparations for 24 hour plasma level curves, 24 hour 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. In order to maintain therapeutic plasma levels and to minimise adverse effects that may occur with high plasma lithium levels, Priadel needs to be administered in divided dosages rather than as a single daily dose.