"Scientists at the National Institutes of Health report they have discovered in mouse studies that a small molecule released in the spinal cord triggers a process that is later experienced in the brain as the sensation of itch.
Application of 14C-labeled mupirocin ointment to the lower arm of normal male subjects followed by occlusion for 24 hours showed no measurable systemic absorption ( < 1.1 nanogram mupirocin per milliliter of whole blood). Measurable radioactivity was present in the stratum corneum of these subjects 72 hours after application.
Following intravenous or oral administration, mupirocin is rapidly metabolized. The principal metabolite, monic acid, is eliminated by renal excretion, and demonstrates no antibacterial activity. In a study conducted in seven healthy adult male subjects, the elimination half-life after intravenous administration of mupirocin was 20 to 40 minutes for mupirocin and 30 to 80 minutes for monic acid. The pharmacokinetics of mupirocin has not been studied in individuals with renal insufficiency.
Microbiology: Mupirocin is an antibacterial agent produced by fermentation using the organism Pseudomonas fluorescens. It is active against a wide range of gram-positive bacteria including methicillin-resistant Staphylococcus aureus (MRSA). It is also active against certain gram-negative bacteria. Mupirocin inhibits bacterial protein synthesis by reversibly and specifically binding to bacterial isoleucyl transfer-RNA synthetase. Due to this unique mode of action, mupirocin demonstrates no in vitro cross-resistance with other classes of antimicrobial agents.
Resistance occurs rarely. However, when mupirocin resistance does occur, it appears to result from the production of a modified isoleucyl-tRNA synthetase. High-level plasmid-mediated resistance (MIC > 1024 mcg/mL) has been reported in some strains of S. aureus and coagulase-negative staphylococci.
Mupirocin is bactericidal at concentrations achieved by topical administration. However, the minimum bactericidal concentration (MBC) against relevant pathogens is generally eight-fold to thirty-fold higher than the minimum inhibitory concentration (MIC). In addition, mupirocin is highly protein bound ( > 97%), and the effect of wound secretions on the MICs of mupirocin has not been determined.
Mupirocin has been shown to be active against most strains of Staphylococcus aureus and Streptococcus pyogenes, both in vitro and in clinical studies. (See INDICATIONS AND USAGE.) The following in vitro data are available, BUT THEIR CLINICAL SIGNIFICANCE IS UNKNOWN. Mupirocin is active against most strains of Staphylococcus epidermidis and Staphylococcus saprophyticus.
The efficacy of topical Bactroban Ointment (mupirocin) in impetigo was tested in two studies. In the first, patients with impetigo were randomized to receive either Bactroban Ointment (mupirocin) or vehicle placebo t.i.d. for 8 to 12 days. Clinical efficacy rates at end of therapy in the evaluable populations (adults and pediatric patients included) were 71% for Bactroban Ointment (mupirocin) (n=49) and 35% for vehicle placebo (n=51). Pathogen eradication rates in the evaluable populations were 94% for Bactroban Ointment (mupirocin) and 62% for vehicle placebo. There were no side effects reported in the group receiving Bactroban Ointment (mupirocin) .
In the second study, patients with impetigo were randomized to receive either Bactroban Ointment (mupirocin) t.i.d. or 30 to 40 mg/kg oral erythromycin ethylsuccinate per day (this was an unblinded study) for 8 days. There was a follow-up visit 1 week after treatment ended. Clinical efficacy rates at the follow-up visit in the evaluable populations (adults and pediatric patients included) were 93% for Bactroban Ointment (mupirocin) (n=29) and 78.5% for erythromycin (n=28). Pathogen eradication rates in the evaluable patient populations were 100% for both test groups. There were no side effects reported in the Bactroban Ointment (mupirocin) group.
There were 91 pediatric patients aged 2 months to 15 years in the first study described above. Clinical efficacy rates at end of therapy in the evaluable populations were 78% for Bactroban Ointment (mupirocin) (n=42) and 36% for vehicle placebo (n=49). In the second study described above, all patients were pediatric except two adults in the group receiving Bactroban Ointment (mupirocin) . The age range of the pediatric patients was 7 months to 13 years. The clinical efficacy rate for Bactroban Ointment (mupirocin) (n=27) was 96%, and for erythromycin it was unchanged (78.5%).
Last reviewed on RxList: 10/4/2010
This monograph has been modified to include the generic and brand name in many instances.
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