Immune System Disorders
Systemic allergic reactions, including anaphylaxis, urticaria, angioedema, and generalized rash
[see
Warnings and Precautions (5.1)]
.
Risk Summary
There are insufficient human data to establish whether there is a drug-associated risk with mupirocin cream in pregnant women. Systemic absorption of mupirocin through intact human skin is minimal following topical administration of mupirocin cream
[see
Clinical Pharmacology (12.3)]
. No developmental toxicity was observed in rats or rabbits treated with mupirocin subcutaneously during organogenesis at doses of 160 or 40 mg per kg per day, respectively (22 and 11 times the human topical dose based on calculations of dose divided by the entire body surface area).
The estimated background risk of major birth defects and miscarriage for the indicated population is unknown. The estimated background risk in the U.S. general population of major birth defects is 2% to 4% and of miscarriage is 15% to 20% of clinically recognized pregnancies.
Data
Animal Data:Developmental toxicity studies have been performed with mupirocin administered subcutaneously to rats and rabbits at doses up to 160 mg per kg per day during organogenesis. This dose is 22 and 43 times, respectively, the human topical dose (approximately 60 mg mupirocin per day) based on calculations of dose divided by the entire body surface area. Maternal toxicity was observed (body weight loss/decreased body weight gain and reduced feeding) in both species with no evidence of developmental toxicity in rats. In rabbits, excessive maternal toxicity at the high dose precluded the evaluation of fetal outcomes. There was no developmental toxicity in rabbits at 40 mg per kg per day, 11 times the human topical dose based on calculations of dose divided by the entire body surface area.
Mupirocin administered subcutaneously to rats in a pre- and postnatal development study (dosed during late gestation through lactation) was associated with reduced offspring viability in the early postnatal period at a dose of 106.7 mg per kg, in the presence of injection site irritation and/or subcutaneous hemorrhaging. This dose is 14 times the human topical dose based on calculations of dose divided by the entire body surface area. The no-observed adverse effect level in this study was 44.2 mg per kg per day, which is 6 times the human topical dose.
Risk Summary
It is not known whether mupirocin is present in human milk, has effects on the breastfed child, or has effects on milk production. However, breastfeeding is not expected to result in exposure of the child to the drug due to the minimal systemic absorption of mupirocin in humans following topical administration of mupirocin cream
[see
Clinical Pharmacology (12.3)]
. The developmental and health benefits of breastfeeding should be considered along with the mother's clinical need for mupirocin cream and any potential adverse effects on the breastfed child from mupirocin cream or from the underlying maternal condition.
Clinical Considerations
To minimize oral exposure of the drug to children, a breast and/or nipple being treated with mupirocin cream should be thoroughly washed prior to breastfeeding.
Absorption
Systemic absorption of mupirocin through intact human skin is minimal. The systemic absorption of mupirocin was studied following application of mupirocin cream 3 times daily for 5 days to various skin lesions greater than 10 cm in length or 100 cm
2in area in 16 adults (aged 29 to 60 years) and 10 children (aged 3 to 12 years). Some systemic absorption was observed as evidenced by the detection of the metabolite, monic acid, in urine. Data from this trial indicated more frequent occurrence of percutaneous absorption in children (90% of subjects) compared with adults (44% of subjects); however, the observed urinary concentrations in children (0.07 to 1.3 mcg per mL [1 pediatric subject had no detectable level]) are within the observed range (0.08 to 10.03 mcg per mL [9 adults had no detectable level]) in the adult population. In general, the degree of percutaneous absorption following multiple dosing appears to be minimal in adults and children.
The effect of the concurrent application of mupirocin cream with other topical products has not been studied
[see
Dosage and Administration (2)]
.
Elimination
In a trial conducted in 7 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.
Metabolism:Following intravenous or oral administration, mupirocin is rapidly metabolized. The principal metabolite, monic acid, demonstrates no antibacterial activity.
Excretion:Monic acid is predominantly eliminated by renal excretion.
Mechanism of Action
Mupirocin inhibits bacterial protein synthesis by reversibly and specifically binding to bacterial isoleucyl-transfer RNA (tRNA) synthetase.
Mupirocin is bactericidal at concentrations achieved by topical administration. Mupirocin is highly protein bound (greater than 97%) and the effect of wound secretions on the minimum inhibitory concentrations (MICs) of mupirocin has not been determined.
Resistance
When mupirocin resistance occurs, it results from the production of a modified isoleucyl-tRNA synthetase, or the acquisition of, by genetic transfer, a plasmid mediating a new isoleucyl-tRNA synthetase. High-level plasmid-mediated resistance (MIC ≥512 mcg/mL) has been reported in increasing numbers of isolates of
S. aureusand with higher frequency in coagulase-negative staphylococci. Mupirocin resistance occurs with greater frequency in methicillin-resistant than methicillin-susceptible staphylococci.
Cross Resistance
Due to its mode of action, mupirocin does not demonstrate cross resistance with other classes of antimicrobial agents.
Antimicrobial Activity
Mupirocin has been shown to be active against susceptible isolates of
S. aureusand
S. pyogenes, both
in vitroand in clinical trials
[see
Indications and Usage (1)]
. The following
in vitrodata are available, but their clinical significance is unknown. Mupirocin is active against most isolates of
Staphylococcus epidermidis.
Susceptibility Test Methods
High-level mupirocin resistance (≥512 mcg/mL) may be determined using standard disk diffusion or broth microdilution tests.
1,2Because of the occurrence of mupirocin resistance in methicillin-resistant
S. aureus(MRSA), it is appropriate to test MRSA populations for mupirocin susceptibility prior to the use of mupirocin using a standardized method.
3,4,5
Pediatrics
There were 93 pediatric subjects aged 2 weeks to 16 years enrolled per protocol in the secondarily infected skin lesion trials, although only 3 were younger than 2 years of age in the population treated with mupirocin cream. Subjects were randomized to either 10 days of topical mupirocin cream 3 times daily or 10 days of oral cephalexin (250 mg 4 times daily for subjects greater than 40 kg or 25 mg per kg per day oral suspension in 4 divided doses for subjects less than or equal to 40 kg). Clinical efficacy at follow-up (7 to 12 days post-therapy) in the per-protocol populations was 97.7% (43 of 44) for mupirocin cream and 93.9% (46 of 49) for cephalexin.
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