Pharmacologic Classification: Antibacterial.
Pharmacology: Mupirocin is a naturally occurring antibiotic produced by fermentation using the microorganism Pseudomonas fluorescens. It inhibits bacterial protein synthesis by reversibly and specifically binding to bacterial isoleucyl transfer-RNA synthetase. Due to its unique mode of action, mupirocin shows no cross resistance with other classes of antibiotics including erythromycin, fusidic acid, gentamicin, lincomycin, methicillin, neomycin, novobiocin, penicillin, streptomycin, chloramphenicol, or tetracycline.
Mupirocin is bactericidal at concentrations achieved with topical application. The minimum bactericidal concentration (MBC) of the drug against Staphylococcus aureus is usually eight to 32 times higher than the minimum inhibitory concentration (MIC) of the drug. The effect of wound secretions on the MICs of mupirocin has not been determined.
Based on in vitro studies, mupirocin's antibacterial activity is enhanced at a slightly acidic pH than at neutral or alkaline pH. It is inactivated at pH less than 4 or greater than 9. The normal skin pH (approximately 5.5) presumably contributes to the activity of mupirocin when applied topically to the skin.
Pharmacokinetics: Bioavailability: Mupirocin does not appear to be appreciably absorbed into the systemic circulation after topical application to intact skin. However, when the drug is applied to broken or diseased skin, the drug may be absorbed into deeper epidermis and possibly into the systemic circulation.
About 95% to 97% of mupirocin is highly bound to serum proteins in vitro.
Any systemically absorbed mupirocin is eliminated from the body by de-esterification of the drug to its inactive metabolite, monic acid, which is rapidly excreted in the urine.