Evidence that method of use, dose and duration of treatment with benzoyl peroxide and tetracycline determines response of acne.

Treatment of acne prior to referral was recorded retrospectively in 72 patients alleged to have responded inadequately; 60% had used benzoyl peroxide (BP) but most applied it to lesions only. Although 86% had used tetracycline, most did not take it correctly for maximum absorption and took less than 1 g/day. Most patients used both drugs for less than three months. Eight-two patients referred because of inadequate response were treated with: (I) 5% benzoyl peroxide (BP) (23 patients); (II) 5% BP and 0.5 g/day oxytetracycline (OTC) (24 patients); (III) 5% BP and 1 g/day OTC (18 patients); (IV) 5% BP and 1.5 g/day OTC (17 patients). BP was applied incrementally from 30 min up to 8-10 hours daily to the entire area affected and OTC taken as a single morning dose. Median grade of severity (0-10 analogue scale) fell by 2 in Groups I and II (P less than 0.05), by 2.5 in Group III (P less than 0.05) and by 3 in Group IV (P less than 0.05); number of lesions fell by 56% +/- 7% (s.e.), (P less than 0.001) 70% +/- less than 10% (P less than 0.001), 75% +/- 8% (P less than 0.001) and 78% +/- 10% (P less than 0.001) respectively and treatment was well tolerated. Thus, although effective drugs are frequently prescribed in acne, method of use, dose and duration are likely to determine response.