Bactroban Ointment 5 g

Mupirocin is a topical antibiotic used to treat certain bacterial skin infections and, in some cases, to clear nasal carriage of Staphylococcus aureus. It works where it is applied and is generally absorbed only in very small amounts, which helps limit effects on the rest of the body. To help reduce the risk of resistance, it should be used exactly as prescribed and for the recommended length of time.

Side effects and precautions

Mupirocin is usually well tolerated, but local reactions such as burning, stinging and itching can happen after it is applied to the skin. Some mupirocin products are made in a macrogol base. These formulations are not suitable for use on mucous membranes and should be used with caution in people with extensive burns or wounds because of the risk of macrogol toxicity. Extra care is also needed in people with kidney impairment.

How it works against bacteria

Mupirocin is an antibacterial medicine that stops bacteria making proteins by binding to isoleucyl transfer RNA synthetase. It is mainly bacteriostatic at low concentrations, although it is usually bactericidal at the high concentrations reached when applied to the skin. At these concentrations, it may also have some activity against organisms reported to be relatively resistant to mupirocin in vitro. It is mainly active against Gram-positive aerobes.

Most strains of staphylococci, including methicillin-resistant and multiply resistant Staph. aureus, and streptococci are susceptible in vitro, although enterococci are relatively resistant. Mupirocin is also active against Listeria monocytogenes and Erysipelothrix rhusiopathiae. Gram-negative organisms are generally insensitive, but Haemophilus influenzae, Neisseria spp. and a few others are sensitive.

Anaerobic organisms, both Gram-positive and Gram-negative, are generally resistant, and activity against fungi is low. Mupirocin is more active in vitro at an acidic pH than under alkaline conditions. Naturally resistant strains of Staph. aureus are rare, but resistance, including high-level plasmid-mediated transferable resistance, has emerged, particularly during long-term use. There has been some concern that inappropriate prescribing of mupirocin has led to steadily increasing resistance.

Activity against fungi

The in vitro activity of mupirocin 2% against Candida albicans was comparable to that of other commonly used topical antifungals. Although MICs were considerably higher than those reported for susceptible bacteria, clinical responses in 10 patients suggested that adequate concentrations of mupirocin were achieved after topical application.

Pharmacokinetics

Only very small amounts of mupirocin applied to the skin are absorbed into the systemic circulation, where it is rapidly metabolised to monic acid, which is excreted in the urine.

Uses and administration

Mupirocin is an antibacterial produced by Pseudomonas fluorescens. It is applied topically as a 2% ointment in a macrogol base, or as a cream containing mupirocin calcium equivalent to 2% mupirocin, to treat various bacterial skin infections. These preparations should be applied up to 3 times daily for up to 10 days; treatment should be reviewed if there is no response after 3 to 5 days.

These preparations are not suitable for use on mucous membranes. Instead, a nasal ointment containing mupirocin calcium equivalent to 2% mupirocin in a paraffin base is used to eradicate nasal carriage of Staphylococcus aureus, particularly epidemic methicillin-resistant strains.

The nasal ointment should be applied inside each nostril 2 or 3 times daily for a maximum of 7 days.