Increases in creatine kinase with atorvastatin treatment are not associated with decreases in muscular performance

• CK increased slightly with atorvastatin, suggesting low-level muscle injury.
• More subjects on atorvastatin doubled their CK level at 6 months.
• CK increases with atorvastatin were not associated with changes in muscle function.
• CK increases with atorvastatin did not predict the incidence of myalgia.
• Increased CK is not necessarily indicative of statin-associated myopathy.

BackgroundThe present study examined if increases in creatine kinase (CK) levels during high-dose atorvastatin treatment are associated with changes in skeletal muscle function and symptoms.MethodsThe Effect of Statins on Muscle Performance study (STOMP) investigated the effects of atorvastatin 80 mg daily for 6 months on muscle performance, exercise capacity, and the incidence of statin-associated muscle complaints in healthy adults.ResultsCK levels increased with atorvastatin (n = 202) from 132.3 ± 120.9 U/L (mean ± SD) at baseline to 159.7 ± 170.4 and 153.1 ± 139.4 U/L at 3 and 6 months, respectively (P ≤ 0.002 for both). Changes in CK with atorvastatin treatment were not associated with changes in muscle function or the incidence of myalgia. More subjects on atorvastatin (n = 24) compared to placebo (n = 12 of 217) doubled their CK level at 6 months (P = 0.02). No differences in muscle function or physical activity were observed between atorvastatin-treated subjects who did or did not double their CK.ConclusionsResults of the present investigation extend the findings of STOMP by demonstrating that greater increases in CK levels with high-dose atorvastatin treatment did not deleteriously impact skeletal muscle function or predict skeletal muscle complaints.This study was registered at ClinicalTrials.gov (NCT00609063).