Exposure of atorvastatin is unchanged but lactone and acid metabolites are increased several-fold in patients with atorvastatin-induced myopathy

Background. The most serious side effect from statin treatment is myopathy, which may proceed to rhabdomyolysis. This is the first study to investigate whether the pharmacokinetics of either atorvastatin or its metabolites, or both, is altered in patients with atorvastatin-related myopathy compared with healthy controls. Methods. A 24-hour pharmacokinetic investigation was performed in 14 patients with atorvastatin-related myopathy. Relevant polymorphisms in SLCO1BJ1 (encoding organic anion transporting polypeptide 1B1), MDR1/ABCB1 (encoding P-glycoprotein), and CYP3A5 (encoding cytochrome P450 3A5) were determined. Data from 15 healthy volunteers were used as controls. Results. No statistically significant difference in systemic exposure of atorvastatin was observed between the 2 groups. However, patients with atorvastatin-related myopathy had 2.4-fold and 3.1-fold higher systemic exposures of the metabolites atorvastatin lactone (P < .01) and p-hydroxyatorvastatin (P < .01), respectively, compared with controls. There were no differences in frequencies of SLCO1B1, MDR1, and CYP3A5 polymorphisms between the 2 groups. Conclusions. This study disclosed a distinct difference in the pharmacokinetics of atorvastatin metabolites between patients with atorvastatin-related myopathy and healthy control subjects. These results are of importance in the further search for the mechanism of statin-induced myopathy.