Transdermal penetration of topical drugs used in the treatment of acne.

Acne vulgaris is a very common skin disease. Most patients present with mild to moderate acne comedonica or papulopustulosa grade I-II. The first-line treatment for these cases is generally via the topical route, whereas systemic medication is indicated when higher severity grades with small nodes or scarring occur. There are several topical agents available that affect at least one of the main pathogenetic factors responsible for the development of acne: hyperseborrhoea, hyperkeratosis, microbial colonisation and inflammatory and immunological reactions. Topical retinoids have a comedolytic and anticomedogenic activity, and some of them have anti-inflammatory potency. Azelaic acid and benzoyl peroxide have a moderate to strong antibacterial effect without inducing bacterial resistance, which is becoming a significant problem with the increasing use of topical antibacterials. Topical antiandrogens may soon be available for the treatment of the pathogenetic factor hyperseborrhoea. The transdermal penetration and the resulting systemic bioavailability of the various topical agents has not been widely considered. Apart from the retinoids, which can be associated with the risk of embryotoxicity/teratogenicity, and clindamycin, which might cause pseudomembranous colitis, information on the systemic pharmacokinetics of other topical agents is not readily available. There is still no consensus on the safe use of topical retinoids in pregnancy, and the occurrence of pseudomembranous colitis after the topical use of clindamycin does not appear to be of clinical relevance. In general, topical anti-acne agents are well tolerated and, as would be expected from their limited transdermal uptake, other significant safety concerns have not so far arisen.