Making sense of the effects of the cumulative dose of isotretinoin in acne vulgaris

BackgroundThe importance of the cumulative dose of isotretinoin with respect to relapse of acne vulgaris remains controversial. Although guidelines recommend 0.5-1.0 mg/kg/d to a minimum cumulative dose of 120 mg/kg, there has been a trend toward the use of lower daily dosages with no reference to cumulative dose. ObjectivesThis study aimed to determine the influence of daily and cumulative dosage on relapse in acne. MethodsCharts of patients with acne treated with isotretinoin were reviewed. Demographic details and daily cumulative doses and duration were compared between patients who received one course and two or more courses, respectively. ResultsOf 1453 patients, 326 (22.4%) received a second course of treatment (study population). The remainder served as controls (n = 1127). Dosage varied from 10 mg/week to 1.1 mg/kg/d, cumulative dosage from 1 to >300 mg/kg, and duration of treatment from 8 weeks to 5 years. Compared with controls, patients who received a second course were more likely to be women (61 vs. 47%; P < 0.001) and received higher daily (0.71 vs. 0.58 mg/kg/d; P < 0.001) and cumulative (126 vs. 101 mg/kg; P < 0.001) doses. Patients treated with very low doses (e.g. 10 mg three times per week) and/or low cumulative doses (e.g. 25-50 mg/kg) did not relapse more often than controls. ConclusionsNeither daily nor cumulative dosages influenced relapse of acne vulgaris in patients treated with varying doses of isotretinoin as long as treatment was continued for 2 months after the acne had completely resolved.