Mupirocin: a topical antibiotic with a unique structure and mechanism of action.

The chemistry, mechanism of action, antimicrobial activity, pharmacokinetics, clinical efficacy, adverse effects, dosage, and administration of mupirocin are reviewed. Mupirocin, formerly termed pseudomonic acid A, is a topical antibiotic under investigation for the treatment of impetigo and other superficial primary and secondary skin infections. Mupirocin (Bactroban, Beecham Laboratories) is currently formulated as a 2% ointment in a water-miscible polyethylene glycol base. The drug is a unique antimicrobial agent because of its structure and mechanism of action. Mupirocin apparently exerts its antimicrobial activity by reversibly inhibiting isoleucyl-transfer RNA, thereby inhibiting bacterial protein and RNA synthesis. Mupirocin has excellent in vitro activity against staphylococci and most streptococci but less activity against other gram-positive and gram-negative bacteria. The drug will only be used topically because of its rapid and extensive systemic metabolism. Several controlled clinical trials documented that mupirocin was significantly better than the polyethylene glycol vehicle alone or ampicillin and as effective as cloxacillin, dicloxacillin, or erythromycin in producing clinical and bacteriological cures in patients with impetigo and wound infections caused by gram-positive pathogens. Limited studies suggest that mupirocin may also have a role in eradicating nasal carriage of staphylococci. Reported adverse effects are local and may be related to the polyethylene glycol vehicle base. Mupirocin should be useful for treating patients with impetigo and wound infections caused by Staphylococcus aureus. However, additional controlled, comparative clinical studies are needed to identify the role of mupirocin in treating other primary and secondary skin infections and for eliminating nasal carriage of staphylococci.