Pharmacokinetics
Following single or repeated intranasal applications of 0.2 gram of BACTROBAN NASAL 3 times daily for 3 days to 5 healthy adult male subjects, no evidence
of systemic absorption of mupirocin was demonstrated. The dosage regimen used
in this study was for pharmacokinetic characterization only. (See DOSAGE
AND ADMINISTRATION for proper clinical dosing information.)
In this study, the concentrations of mupirocin in urine and of monic acid in
urine and serum were below the limit of determination of the assay for up to
72 hours after the applications. The lowest levels of determination of the assay
used were 50 ng/mL of mupirocin in urine, 75 ng/mL of monic acid in urine, and
10 ng/mL of monic acid in serum. Based on the detectable limit of the urine
assay for monic acid, one can extrapolate that a mean of 3.3% (range: 1.2 to
5.1%) of the applied dose could be systemically absorbed from the nasal mucosa
of adults.
Data from a report of a pharmacokinetic study in neonates and premature infants
indicate that, unlike in adults, significant systemic absorption occurred following
intranasal administration of BACTROBAN NASAL in this population. At this
time, the pharmacokinetic properties of mupirocin following intranasal application
of BACTROBAN NASALhave not been adequately characterized in neonates or other
children less than 12 years of age, and in addition, the safety of the product
in children less than 12 years of age has not been established.
The effect of the concurrent application of intranasal mupirocin calcium ointment,
2% with other intranasal products has not been studied. (See PRECAUTIONS:
DRUG INTERACTIONS)
Following intravenous or oral administration, mupirocin is rapidly metabolized.
The principal metabolite, monic acid, demonstrates no antibacterial activity.
In a study 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. Monic acid is predominantly eliminated
by renal excretion. 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. Mupirocin inhibits bacterial protein synthesis
by reversibly and specifically binding to bacterial isoleucyl transfer-RNA synthetase.
Due to this mode of action, mupirocin demonstrates no in vitro cross-resistance
with other classes of antimicrobial agents.
When mupirocin resistance does occur, it appears to result from the production
of a modified isoleucyl-tRNA synthetase. High-level plasmid-mediated resistance
(MIC > 1,024 mcg/mL) has been reported in some strains of Staphylococcus
aureus and coagulase-negative staphylococci.
Mupirocin is bactericidal at concentrations achieved topically by intranasal
administration. However, the minimum bactericidal concentration (MBC) against
relevant intranasal pathogens is generally 8-fold to 30-fold higher than the
minimum inhibitory concentration (MIC). In addition, mupirocin is highly protein
bound ( > 97%), and the effect of nasal secretions on the MICs of intranasally
applied mupirocin has not been determined.
Mupirocin has been shown to be active against most strains of methicillin-resistant
S. aureus, both in vitro and in clinical studies of the eradication
of nasal colonization. BACTROBAN NASALonly has established clinical utility
in nasal eradication as part of a comprehensive program to curtail institutional
outbreaks of infections with methicillin-resistant S. aureus. (See INDICATIONS)
The following in vitro data are available, but their clinical significance
is unknown.
Mupirocin exhibits in vitro MICs of 1 mcg/mL or less against most ( > 90%)
strains of methicillin-susceptible S. aureus; however, the safety and
effectiveness of mupirocin calcium in eradicating nasal colonization of and
preventing subsequent infections due to methicillin-susceptible S. aureus
have not been established.
Last updated on RxList: 12/9/2008