Lithium toxicity and mefenamic acid. A possible interaction and the role of prostaglandin inhibition.

An elderly patient with bipolar manic-depressive psychosis, stabilised satisfactorily on lithium carbonate, developed acute symptoms of lithium toxicity shortly after commencing mefenamic acid. Vulnerability factors for the interaction may have included age, history of cardiac failure, and impaired glomerular function. It is hypothesised that the interaction may have been mediated by inhibition of prostaglandin activity.