Safety of long-term high-dose minocycline in the treatment of acne.

Minocycline is widely used as a second-line antimicrobial for acne vulgaris. Some patients require doses of up to 200 mg daily to control their acne. To assess the long-term safety of minocycline when used at higher doses, 700 patients treated with minocycline at doses of 100 mg daily, 100/200 mg on alternate days and 200 mg daily, were recruited. The mean duration of treatment was 10.5 months. Side-effects were monitored and full blood count, blood urea, electrolytes and liver function tests were carried out on 200 of the 700 patients. Side-effects were recorded in 13.6%, and included vestibular disturbance, candida infection, gastrointestinal disturbance, cutaneous symptoms (pigmentation, pruritus, photosensitive rash and urticaria) and benign intracranial hypertension. Pigmentation was the only side-effect found to be significantly increased in patients taking higher doses of minocycline, as compared with lower doses (P < 0.01). All patients with pigmentation had taken a total cumulative dose of over 70 g. No significant abnormalities were found in any of the haematological and biochemical profiles. We conclude that minocycline, at doses of up to 200 mg/day, is safe, long-term, for acne, when such doses are clinically necessary.