Topical antibiotics are used widely in the USA where there are several brands of erythromycin and tetracycline and one of clindamycin.22 In Europe also there are several topical antibiotics for the treatment of acne. In the UK the topical anti-acne antibiotics are chloramphenicol,  Neo-Medrone (methyl-prednisolone acetate and  neomycin sulphate),  tetracycline, erythromycin and clindamycin. Chloramphenicol is bacteriostatic for P. acnes, on which neomycin has no effect whatsoever, so why Neo-Medrone helps subjects with acne (if it does) is a  mystery.

 

  As  with  benzoyl  peroxide,   concentration  and dose-response studies of the different  antibiotics  are virtually nonexistent though comparative  studies suggest  that  clindamycin is more  effective than  tetracycline. There are few  studies comparing nonantibiotic and antibiotic topical acne therapies. One study showed virtually no difference between erythromycin and benzoyl peroxide.14 Another showed that benzoyl peroxide was superior to chrloramphenicol (available as in Actinac).

  The  mechanism of action of the topical antibiotics is predominantly antimicrobial. This is especially so with clindamycin which has been  shown  significantly  to reduce  both the  surface  and ductal  counts of P. acnes. Erythromycin and tetracycline do not usually significantly decrease surface numbers of P. acnes but they and clindamycin will reduce surface free fatty acids by 40-50 per cent. The  effect  of topical  antibiotics on follicular  casts has  not been investigated,  though  clinical enumeration of  lesions shows  a significant reduction in the number of comedones. This is more likely to be an indirect rather than a  primary effect.

 

  Although systemic antibiotics have nonarttimicrobial anti-inflammatory  effects it  is unlikely  that  topical antibiotics work  predominantly through these mechanisms.