Topical antibiotics are helpful in acne vulgaris and acne rosacea and probably in reducing the frequency of infections related to intravenous catheters. One drug, mupirocin (Bactroban), is effective in treating impetigo contagiosa. Mupirocin binds to bacterial isoleucyl-transfer RNA synthetase and prevents the incorporation of isoleucine into protein sequences. Mupirocin is most effective against gram-positive bacteria. Toxicity is uncommon.
Another topical antibiotic, metronidazole, is effective in the treatment of acne rosacea. Metronidazole is a synthetic nitroimidazole derivative that reduces inflammation by an unknown mechanism. Other selected topical antibiotics are listed in Table 41.2.