Plus ça change? Switching lithium preparations

AIMS AND METHOD: A supply disruption alert in 2020, now rescinded, notified UK prescribers of the planned discontinuation of Priadel(®) (lithium carbonate) tablets. This service evaluation explored lithium dose and plasma levels before and after the switching of lithium brands, in order to determine the interchangeability of different brands of lithium from a pharmacokinetic perspective. RESULTS: Data on the treatment of 37 patients switched from Priadel(®) tablets were analysed. Switching to Camcolit(®) controlled-release tablets at the same dose did not result in meaningful differences in plasma lithium levels. Dose adjustment and known or suspected poor medication adherence were associated with greater variability in plasma lithium levels on switching brands. CLINICAL IMPLICATIONS: For comparable pre- and post-switch doses in adherent patients, the most common brands of lithium carbonate appear to produce similar plasma lithium levels. British National Formulary guidance relating to switching lithium brands may be unnecessarily complex.