Isotretinoin for the treatment of acne vulgaris: which factors may predict the need for more than one course?

We investigated 299 patients treated 5-10 years ago with isotretinoin, and followed them for 5 years post-treatment. Of the 299 patients 22.7% required repeat courses of treatment; 17% had two courses, 5% had three courses and 1% had 4-5 courses. Response to further treatment was predictably successful, was not associated with any additional adverse reactions, and produced no persistent side-effects. Factors contributing to the need for further courses of treatment included lower dose regimens (0.1 and 0.5 mg/kg), the presence of severe acne, being a female over the age of 25 at the onset of therapy, and having a prolonged history of acne.