Prolonged quinidine half-life with associated toxicity in a patient with hepatic failure.

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 micrograms/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.