Cumulative isotretinoin dosing, treatment response and acne relapse: A randomized controlled trial

Isotretinoin is the most effective treatment for severe acne, but optimal cumulative dosing remains debated. While 120 mg/kg is standard, some advocate higher doses or prolonged treatment to reduce relapse.

To compare acne outcomes between 120 and 150 mg/kg cumulative isotretinoin dosing and to evaluate 12-month relapse and scarring.

In this single-centre, randomized single-blind trial, with blinded outcomes assessment, patients with moderate-to-severe cystic acne were allocated to cumulative isotretinoin doses of 120 or 150 mg/kg. Primary outcomes were changes in total lesion count and acne severity grade (1-8 scale) from baseline to mid-treatment and end of treatment; secondary outcomes included 12-month acne relapse and scarring.

Both cumulative dose groups showed comparable improvements in acne severity and lesion counts from baseline to treatment completion, with no significant differences between groups (all p > 0.20). Scarring did not worsen over the course of treatment. At 12 months after treatment discontinuation, relapse rates were similar between groups: 26.7% in the 120 mg/kg group and 32.3% in the 150 mg/kg group (p = 0.619). Adverse events were mild and comparable.

Single-centre design and retrospective trial registration.

Increasing dosing to 150 mg/kg provides no benefit. Extended therapy does not reduce relapse, supporting 120 mg/kg as optimal. Persistent acne required longer treatment.