MUPIRICOR OINTMENT

Indications

• Eradication of nasal carriage of Staphylococcus aureus, including methicillin-resistant Staphylococcus aureus (MRSA)
• Treatment of skin infections caused by susceptible bacteria, including impetigo and folliculitis

Dosage

Adults: For nasal carriage eradication, apply 2-3 times a day for 5 days, with the dose applied to the inner surface of each nostril. For

Mechanism of action

Mupirocin specifically and reversibly binds to bacterial isoleucyl transfer-RNA (tRNA) synthetase, inhibiting the enzyme that converts isoleucine and tRNA to isoleucyl-tRNA. This inhibition leads to decreased bacterial protein and RNA synthesis, resulting in bacteriostatic effects at lower concentrations and bactericidal effects with prolonged exposure, killing 90-99% of susceptible bacteria over 24 hours.

Pharmacodynamics

Mupirocin is effective against susceptible aerobic gram-positive cocci, particularly Staphylococcus aureus, Staphylococcus epidermidis, and beta-hemolytic streptococci such as Streptococcus pyogenes. Its antibacterial activity is attributed to its ability to inhibit protein synthesis, which is crucial for bacterial survival. Clinical studies have shown a therapeutic response rate of 94 to 98% after one week of treatment for conditions like impetigo, with over 90% of patients demonstrating clinical improvement in primary and secondary skin infections.

Pharmacokinetics

Mupirocin is primarily used topically, resulting in minimal systemic absorption. When applied to the skin, it is rapidly absorbed and achieves high local concentrations. The drug is metabolized in the liver and excreted in urine. Its pharmacokinetic profile supports its use for localized infections with minimal risk of systemic side effects.

Adverse effects

• Skin reactions
• Nasal mucosal disorder

Interactions

• Caution in patients with sensitivity to sulfonamides
• Caution with significant hepatic impairment
• Caution with significant renal impairment

Precautions

• Monitor for leucopenia
• Use with caution in patients with G6PD deficiency due to risk of hemolysis
• Avoid use in pregnancy unless potential benefit outweighs risk due to risk of neonatal hemolysis and methaemoglobinaemia in the third trimester

Pregnancy

Manufacturer advises avoiding unless potential benefit outweighs risk-no information available.

Breast-feeding

Small risk of kernicterus in jaundiced infants and of haemolysis in G6PD-deficient infants.

Storage

Store at room temperature, away from moisture and heat.

Formulations

• Mupirocin 20 mg per 1 gram cream
• Mupirocin nasal spray

Mechanism of action

Mupirocin specifically and reversibly binds to bacterial isoleucyl transfer-RNA (tRNA) synthetase, which is an enzyme that promotes the conversion of isoleucine and tRNA to isoleucyl-tRNA. Inhibition of this enzyme subsequently leads to the inhibition of the bacterial protein and RNA synthesis. Mupirocin is bacteriostatic at lower concentrations but it exerts bactericidal effects with prolonged exposure, killing 90-99% of susceptible bacteria over a 24 hour period.

Pharmacodynamics

Mupirocin is reported to be active against susceptible aerobic gram-positive cocci, such as _Staphylococcus aureus_, _Staphylococcus epidermidis_, and other beta-hemolytic streptococci_Streptococcus pyogenes_. It mediates its antibacterial activity by inhibiting the bacterial protein synthesis and formation of bacterial proteins essential for survival. The minimum bactericidal concentration (MBC) against relevant pathogens is generally eight-fold to thirty-fold higher than the minimum inhibitory concentration (MIC). In one clinical study investigating the therapeutic effectiveness of topical mupirocin in impetigo, the therapeutic response rate was about 94 to 98% after one week following the end of therapy. In clinical studies of patients with primary and secondary skin infections, both elimination of the bacterial pathogen and clinical cure or improvement hav been demonstrated in over 90% of patients receiving topical mupirocin. Mupirocin resistance as high as 81% has been reported previously. Resistance to mupirocin, which occurs more frequently in methicillin-resistant than methicillin-susceptible staphylococci, may occur with the production of a modified isoleucyl-tRNA synthetase, or the acquisition of, by genetic transfer, a plasmid mediating a new isoleucyl-tRNA synthetase.