Topical Antibiotics: Introduction
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Topical antibiotics play an important role in the management of many common dermatologic conditions (Table 218-1). They are prescribed most often by dermatologists for the management of mild-to-moderate acne vulgaris or as adjunctive treatment with oral agents. For localized superficial infections, such as impetigo, the use of a topical agent (e.g., mupirocin or retapamulin) may eliminate the need for oral antibiotics and the accompanying problems of compliance, gastrointestinal side effects, and potential drug interactions. Topical antibiotics are still frequently prescribed as prophylactic agents after minor surgery or cosmetic procedures (chemical peel or laser resurfacing) to reduce the risk of postoperative wound infection and to speed wound healing. The use of topical antibiotics for prophylaxis after such minor procedures has been proven to be unnecessary and incurs risk of inducing allergy. Petrolatum is recommended for use after clean surgical procedures.
Name | Form Available | Mechanism of Action | Bacteriaa |
|---|---|---|---|
Bacitracin | O | Cell wall inhibitor | Gr+ |
Polymyxin B | O | Detergent | Gr– |
Gramicidin | O | Ion channel | Gr+ |
Mupirocin | O, C | Transfer RNA inhibitor | Gr+ |
Neomycin | O | 30S ribosome inhibition | Gr− |
Erythromycin | S, G, P, O | 50S ribosome inhibition | Gr± |
Clindamycin | S, G, L | 50S ribosome inhibition | |
Fusidic acid | NA | Interferes with EF-G | |
Silver sulfadiazine | C | ||
Mafenide acetate | O | Enzyme inhibition | Gr± |
Nitrofurazone | C, S | Enzyme inhibition | Gr± |
Metronidazole | G, C, L | Electrochemical | Anaerobes |
Clioquinol | C, O | Unknown | Broad spectrum |
Azelaic acid | C, G | Protein synthesis inhibition | Gr+ |
Agents Used in the Topical Treatment of Acne and Rosacea
The efficacy of topical antibiotics for the treatment of acne vulgaris and rosacea may be due to their direct antibiotic effect, but many of the topical antibiotics exhibit anti-inflammatory properties by suppressing neutrophil chemotactic factor or by other mechanisms.1 There are concerns about the use of topical antibiotics in the treatment of acne vulgaris because of the increasing levels of antibiotic resistance. Combining the antimicrobial benzoyl peroxide with antibiotics reduces the development of antibiotic resistance.
Erythromycin belongs to the group of macrolide antibiotics and is active against both Gram-positive cocci and Gram-negative bacilli. It is used principally as a topical agent in the treatment of acne. Erythromycin binds to the bacterial 50S ribosome and blocks translocation of the peptidyl-transfer RNA (tRNA) molecule from the acceptor to the donor site, interfering with the formation of the polypeptide chain and inhibiting protein synthesis. In addition to its antibacterial properties, erythromycin has anti-inflammatory activity. Erythromycin is available as a 1.5% to 2.0% solution, gel, pledgets, and ointment as a single agent. It is also available in combination with benzoyl peroxide.
Clindamycin is a semisynthetic lincosamide antibiotic that is derived from lincomycin. The mechanism of action is very similar to that of erythromycin, with binding to the 50S ribosome and suppression of bacterial protein synthesis. Clindamycin is used topically as a 1% gel, solution, suspension (lotion), and foam primarily for the treatment of acne. It is also available as a combination with benzoyl peroxide, which may slow the development of antibiotic resistance to clindamycin. Pseudomembranous colitis rarely has been reported to occur with the topical use of clindamycin.2
Metronidazole, a topical nitroimidazole, is currently available as a 0.75% gel, cream, or lotion and as a 1% cream or gel for the topical treatment of rosacea. In the lower strength, it is applied twice daily, and in the higher strength, it is used once daily. Orally, metronidazole has broad-spectrum activity against many protozoal organisms and anaerobes.
