Liberation of lithium from sustained release preparations. A comparison of seven registered brands.

We investigated the rate of release of seven commercial lithium preparations designated as sustained-release preparations and available in Europe and the USA. The examined products release lithium completely within four hours. The rate of liberation from three drugs resembles that of nonsustained-release preparations, three of which were tested under the same conditions. In one case, the comparison between two batches of sustained-release preparations reveals marked differences in quality. Physicians should be aware that some drugs available on the market and designated as sustained-release preparations do not comply with the international standard for this type of formulation.