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We studied the susceptibility of antimicrobial agents to Propionibacterium acnes (P. acnes) and Staphylococcus epidermidis (S. epidermidis) isolated from acne patients. We measured the minimum inhibitory concentrations (MICs) of the following five drugs: roxithromycin (RXM), erythromycin (EM), clindamycin (CLDM), minocycline (MINO) and ofloxacin (OFLX), which are frequently used to treat acne and skin infections. We found many resistant strains of S. epidermidis and some resistant strains of P. acnes. There was a correlation between the resistance of S. epidermidis and the former therapy for acne, but no distinct correlation between the resistance of P. acnes and the former therapy for acne.

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On the basis of reports that erythromycin is effective in the treatment of acne, we investigated whether roxithromycin (ROM), a new derivative of erythromycin, might also be effective in treating acne. Roxithromycin was administered to 30 patients with acne for 8 weeks. General improvement was assessed 8 weeks after the initiation of the therapy with a six-graded scale as follows; 1: good improvement, 2: moderate improvement, 3: slight improvement, 4: no change, 5: worsening, and 6: no assessment. The percentage of good or moderate improvement was 73.3%, and that of good improvement alone was 20.0%. Our results suggest that ROM is effective in the treatment of acne.

The effect of roxithromycin (ROM), a new oral semi-synthetic macrolide, on the generation of reactive oxygen species (ROS), using human neutrophils and a cell-free, xanthine-xanthine oxidase system was examined. The species investigated were the superoxide radical anion (O2-), hydrogen peroxide (H2O2), and the hydroxyl radical (OH.). ROM effectively inhibited the generation of O2-, H2O2 and OH. by human neutrophils. On the other hand, the drug did not markedly affect the ROS levels generated in the xanthine-xanthine oxidase system. The present study indicates that ROM may exert an anti-inflammatory action by inhibiting neutrophil oxygen radical generation at the sites of inflammation.