Prolonged Quinidine Half‐life with Associated Toxicity in a Patient with Hepatic Failure

Abstract

A markedly prolonged quinidine elimination half‐life due to hepatic failure and resultant quinidine toxicity occurred in a 57‐year‐old man with a history of atrial fibrillation. A prolonged QT interval, development of torsades de pointes, and a serum quinidine concentration of 3.1 μg/ml contributed to a decision favoring permanent pacemaker implantation. The apparent quinidine half‐life ranged from 66–99 hours and was associated with QT prolongation and persistent U waves. On discontinuing quinidine, all signs associated with toxicity resolved as serum quinidine concentrations decreased, which resulted in reversal of the decision to implant a permanent pacemaker. This case reports an extremely long quinidine elimination half‐life and reillustrates the importance of drug pharmacokinetics in patient care.