Assessing the Role of Baseline Creatine Kinase Measurement Before Initiating Oral Isotretinoin in Acne Vulgaris Patients: Insights From a Retrospective Cohort of 1256 Individuals

Introduction and Background Isotretinoin is a highly effective treatment for severe acne vulgaris, but it may cause musculoskeletal side effects, including elevations in serum creatine kinase (CK) levels. Current guidelines do not mention routine CK monitoring unless musculoskeletal symptoms are present. This study aimed to evaluate temporal changes in CK levels during isotretinoin therapy to clarify their clinical relevance and inform safer, evidence‐based monitoring strategies. Material and Methods This retrospective observational cohort study included patients treated with oral isotretinoin for acne vulgaris between January 2022 and July 2024. Data were extracted from medical records and included demographics, cumulative isotretinoin dose, and laboratory values (CK, AST, and ALT) assessed at baseline and at the 1st, 2nd, 4th, and 6th months of therapy. Results A total of 1256 patients were analyzed (mean age 19.69 ± 3.9 years); 75.1% were female. The median baseline CK level was 73 U/L (range: 15–5505), and 6.5% ( n = 82) had CK levels ≥ 200 U/L before treatment. By Month 6 ( n = 452), the mean cumulative isotretinoin dose was 4928 ± 324.2 mg, and median CK was 70 U/L (range: 15–4267). During follow‐up, 26 patients showed both CK ≥ 200 U/L and ≥ 5‐fold increases from baseline. However, follow‐up CK levels did not significantly differ from baseline. CK changes were moderately correlated across time points and weakly to moderately correlated with ALT and AST changes. Conclusion Although isotretinoin did not cause a significant overall increase in CK levels, marked individual variability and occasional elevations were observed. Baseline CK assessment may facilitate interpretation of subsequent changes, particularly in patients with muscle‐related symptoms. Moderate correlations between CK and AST suggest a possible muscular contribution to some transaminase elevations. Routine CK monitoring is unnecessary; however, individualized evaluation based on baseline values may improve patient safety. Prospective studies are needed to refine monitoring strategies.