Background: The efficacy of oral isotretinoin in acne has been established, though the role of the mean daily dose (MDD) is still unclear.
Objective: To determine the predictive factors of resistance to oral isotretinoin and the role of the MDD of isotretinoin on relapse of acne while taking into account patient characteristics and the total cumulative dose (TCD).
Methods: Two hundred and thirty-seven patients treated with oral isotretinoin for the first time were enrolled by a single dermatologist. Patients with closed comedonal acne and with hyperandrogenism received adequate therapy prior to isotretinoin.
Results: Closed comedonal acne was the only predictive factor of resistance to isotretinoin with an adjusted OR = 2.7 (95% CI: 1.0-7.3). The estimated rates of relapse at 1, 3 and 5 years were 14, 40 and 48%, respectively. Age and grade of facial acne were the only predictive factors for relapse with adjusted relative risks of 0.6 (95% CI: 0.4-0.8) for age >/= 20 and 1.5 (95% CI: 1.0-2.2) for grade > 3.
Conclusion: MDD, TCD, closed comedonal acne and hyperandrogenism that have been adequately treated prior to isotretinoin treatment had no prognostic value for relapse.