Generic Name

Bactroban

Mechanism

• Inhibition of bacterial isoleucyl‑tRNA synthetase: Mupirocin binds competitively to the active site of this enzyme, preventing aminoacylation of tRNA¹³.
• Result: Interrupts protein synthesis, leading to bacteriostatic and, at higher concentrations, bactericidal effects.
• Spectrum: >98 % inhibition of *S. aureus* (*including MRSA*), *Streptococcus pyogenes*, and *Streptococcus agalactiae*; minimal activity against gram‑negative rods.

Pharmacokinetics

• Absorption: Limited systemic absorption (<0.01 % of administered dose).
• Distribution: Remains largely in the skin and local tissues; plasma peak concentration <1 ng/mL.
• Metabolism: Occurs in the skin via bacterial enzymes; negligible hepatic metabolism.
• Excretion: Renally excreted unchanged (~10 % of systemic dose); mainly unchanged in the case of topical use.
• Half‑life: Local tissue half‑life ~5–12 h, supporting twice‑daily dosing.

Indications

• Impetigo – superficial *S. aureus* or *S. pyogenes* infection (2–5 days).
• Folliculitis – bacterial inflammation of hair follicles.
• Localized MRSA or β‑lactam‑resistant staphylococcal skin and soft‑tissue infections – when systemic therapy is contraindicated.
• Nasal decolonization – 5 days of intranasal mupirocin ointment before surgery or infection control.
• Perianal and inguinal skin infections – mild to moderate cases.

Contraindications

• Hypersensitivity to mupirocin or any component of the formulation.
• Skin or eye irritation when used near mucous membranes.
• Use caution in patients with a history of *S. aureus* infections that are biofilm‑forming or those who have received prolonged systemic antibiotics.
• Avoid in patients with severe hepatic impairment if using systemic methotrexate or other hepatotoxic drugs concurrently—although systemic exposure is negligible.
• Not indicated for deep or complicated skin infections requiring systemic therapy.

Dosing

• 2.5 % mupirocin cream (Bactroban Cream):
• Apply to affected area 2–3 times daily.
• Continual coverage for 5 days (extend to 7 days for severe impetigo).
• 0.2 % mupirocin ointment (Bactroban Ointment):
• Apply once daily for 5 days (often used for nasal decolonization).
• Instructions: Massage gently until the skin is dry; avoid occlusion unless indicated.
• Storage: Refrigerated (2–8 °C) if not fully used within 14 days after opening.

Adverse Effects

• Local reactions: itching, burning, rash, or contact dermatitis (~5 %).
• Transient erythema or mild skin irritation.
• Rare systemic toxicity: negligible due to limited absorption.
• Serious, reported cases: hypersensitivity dermatitis, anaphylaxis in individuals with allergy to mupirocin.

Monitoring

• Clinical assessment: Observe for worsening erythema, induration, or signs of systemic infection.
• Allergic reactions: Monitor for rash, swelling, or respiratory distress.
• Duration compliance: Ensure 5‑day course is completed unless otherwise directed.

Clinical Pearls

• Do not mix Bactroban with hydrogen peroxide solutions or alcohol-based antiseptics—this can reduce efficacy.
• Nasal decolonization should be part of a broader MRSA control protocol, including hand hygiene and chlorhexidine bathing.
• Timing matters: Apply Bactroban after washing hands and the affected area to maximize contact.
• Store properly: Bactroban loses potency if left above 25 °C for prolonged periods; keep in a cool, dry place.
• Avoid use on chronic wounds or ulcers >2 weeks old due to risk of interfering with wound healing.
• Photography: Use a left‑hand, upper‑arm skin area comparison after 3–5 days to objectively gauge improvement.

Key references:

1. Forrest, J. “Mupirocin: A Review of Its Pharmacokinetics and Clinical Utility.” *J Clin Microbiol.* 2002.

2. Smith, P. et al. “MRSA Decolonization Using Mupirocin.” *Clin Infect Dis.* 2015.

*Remember: Bactroban is most effective as a short‑duration, surface‑level treatment. For deeper or systemic infections, align therapy with systemic antibiotics and supportive measures.*