There is variation in the dosing of isotretinoin with daily doses ranging from 0.1 to 2 mg/kg. Typically, 0.5-2 mg/kg/day is recommended for 16-20 weeks to reach a total cumulative dose of 120-150 mg/kg. A lower starting dose may be necessary in patients with significant inflammatory acne to prevent flares in the first month of treatment. Patients at risk for initial flaring may be concomitantly given prednisone to reduce flaring and prevent exuberant granulation tissue. Patients with pyoderma faciale should be controlled on prednisone prior to beginning isotretinoin.
Studies have demonstrated that about 23% of patients using the typical dosing may need to repeat treatment with isotretinoin. 96% of patients who experience a relapse of their acne do so within the first three years. Of patients taking a lower regimen of 0.1 mg/kg/day, 40% need a repeat course (93). Factors contributing to the need for additional courses are lower dose regimens (0.1-0.5 mg/kg/day or cumulatively less than 120 mg/kg), the presence of severe acne, being a female older than 25 years at the start of therapy, and having a prolonged history of acne (94,95). If repeat therapy is needed, at least two to three months should elapse between courses. An even longer interval may be sensible as the effects of isotretinoin can be seen five months after discontinuation.