Background: Acne vulgaris is a common dermatologic disease. Isotretinoin is one of the medications prescribed in severe cases of acne. Despite its high efficacy, isotretinoin use for acne is associated with some side effects. This study was done to evaluate the effects of isotretinoin on serum levels of creatine phosphokinase (CPK) and musculoskeletal symptoms in patients with acne vulgaris.

Methods: This study was done on forty 15- to 30-year-old patients with moderate to severe acne vulgaris recruited from Semnan dermatology clinics in 2010. The participants were all candidates for isotretinoin therapy. Serum CPK levels and musculoskeletal physical exam were checked before the treatment and every 2 months for 6 months. Isotretinoin was prescribed 0.5-1 mg/kg/body weight and continued throughout the study period with the same dosage.

Results: Thirty-three (82.5%) patients were female. The mean (±Standard Deviation) age of the participants was 22.3±3.4 years. The mean serum CPK levels increased significantly, (P< 0.05), 2, 4 and 6 months after the treatment, but they remained below the upper limit of normal range (45-160 IU/L), except in an 18-year old patient, which it was 162 IU/L. Moreover, they did not exhibit noticeable musculoskeletal symptoms. Musculoskeletal symptoms, such as mild myalgia, were reported in 10% of the patients but they were relieved gradually.

Conclusion: It seems that the increase in serum levels of CPK, with or without musculoskeletal symptoms, in patients who are on isotretinoin, is a benign phenomenon. Therefore, we do not recommend measurement of CPK levels in patients with mild myalgia.