Rhabdomyolysis caused by a potential sitagliptin-lovastatin interaction

A 75-year-old woman with diabetes mellitus, hypertension, and hyperlipidemia came to the emergency department with generalized and upper-extremity weakness; she had experienced a fall 2 months earlier. On admission, her drug therapy included lovastatin 40 mg/day, controlled-release diltiazem 240 mg/day, and glimepiride 1 mg/day. Nineteen days earlier, sitagliptin 100 mg/day had been started; it was discontinued 2 weeks later, and glimepiride was begun. A cardiology consultation performed on the day of admission determined that a markedly elevated creatine kinase-myocardial band isoenzyme level and borderline-high troponin I level were diagnostic of rhabdomyolysis secondary to statin use. Because the patient had been taking lovastatin for the past 12 years, the possibility that the rhabdomyolysis may have been caused by a drug interaction between lovastatin and a concomitant drug was evaluated. As it had been 10 months since her last dosage adjustment of diltiazem, it was unlikely that the statin-induced rhabdomyolysis was precipitated by diltiazem. Use of the Drug Interaction Probability Scale to determine the strength of a lovastatin-sitagliptin interaction indicated a possible association (score of 4). Multiple drug interactions have been reported with lovastatin. To our knowledge, however, this is the first case report of a possible sitagliptin-lovastatin interaction that may have caused rhabdomyolysis. Studies must be performed to further evaluate the in vivo effect of sitagliptin on the cytochrome P450 3A4 enzyme system and to elucidate other mechanisms that may potentiate such a drug-drug interaction. In the meantime, however, clinicians should be aware of this possible drug interaction.