Medicine for acne: Isotretinoin Therapy (1)

Dosage.
The severity of the side effects of isotretinoin is proportional to the daily dose. Start with lower dosages and progressively increase the dosage in accordance with the tolerance.
The cumulative dose may be more important than the duration of therapy. A cumulative dose of greater than 120 mg/kg is associated with significantly better long-term remission. This dosage level can be achieved by either 1 mg/kg/day for 4 months or a smaller dosage for a longer period. The therapeutic benefit from a total cumulative dose of more than 150 mg/kg is virtually nonexistent. Analysis of 9 years of experience demonstrated that 1 mg/kg/day of isotretinoin for 4 months resulted in the longest remissions. Relapse rates in patients receiving 0.5 mg/kg/day were approximately 40% and those receiving 1.0 mg/kg/day were approximately 20%. Younger patients, males, and patients with truncal acne derive maximum benefit from the higher dosages. In these patients, dosages less than 0.5 mg/kg/day for a standard 4-month course are associated with a high relapse rate. Treat older patients with facial acne with a dosage of 0.5 mg/kg/day. Double the dosage if there is no response at the end of 2 months. Side effects depend on the dosage and can be controlled through reduction.
Duration of therapy.
A standard course of isotretinoin therapy is 16 to 20 weeks. Approximately 85% of patients are clear at the end of 16 weeks; 15% require longer treatment. Side effects are related to the dosage. Treat for a longer duration at a lower dosage if mucocutaneous side effects become troublesome. Patients with large, closed comedones may respond slowly and relapse early with inflammatory papules. Another ill-defined group responds slowly and requires up to 9 months until the condition begins to clear.
Relapse and repeat courses of isotretinoin.
Approximately 39% of patients relapse and require oral antibiotics (23%) or additional isotretinoin (16%). Relapse usually occurs within the first 3 years after isotretinoin is stopped; most often during the first 18 months after therapy. Some patients require multiple courses of therapy. The response to repeat therapy is consistently successful, and side effects are similar to those of previous courses. Repeat courses of isotretinoin seem to be safe.