Mupirocin Contents and Composition
Mupirocin topical preparations contain 20 mg of mupirocin per gram (2% concentration) in a water-miscible polyethylene glycol ointment base consisting of polyethylene glycol 400 and polyethylene glycol 3350 1.
Active Ingredient
- Mupirocin: A naturally occurring antibiotic with the chemical name (E)-(2S,3R,4R,5S)-5-[(2S,3S,4S,5S)-2,3-Epoxy-5-hydroxy-4-methylhexyl]tetrahydro-3,4-dihydroxy-β-methyl-2H-pyran-2-crotonic acid, ester with 9-hydroxynonanoic acid
- Molecular formula: C26H44O9
- Molecular weight: 500.63
- Concentration: 2% (20 mg per gram of ointment)
Inactive Ingredients (Vehicle Base)
The ointment base is a bland, water-miscible formulation containing:
- Polyethylene glycol 400
- Polyethylene glycol 3350
This polyethylene glycol ointment base (N.F.) provides the vehicle for topical delivery 1.
Mechanism and Clinical Use
Mupirocin works by reversibly inhibiting isoleucyl-transfer RNA synthetase, thereby blocking bacterial protein and RNA synthesis 2, 3. This unique mechanism of action distinguishes it from other topical antibiotics and reduces the likelihood of cross-resistance.
The formulation is FDA-approved for topical treatment of impetigo caused by Staphylococcus aureus and Streptococcus pyogenes 1. Multiple guidelines recommend applying mupirocin ointment to lesions 2-3 times daily for patients with limited skin lesions 4, 5, 6, 7.
Important Clinical Considerations
- The water-miscible polyethylene glycol base allows for easy application and removal
- Local adverse effects (burning, itching, redness) occur in less than 3% of patients and are often related to the vehicle base itself 2, 8
- Mupirocin undergoes rapid systemic metabolism, making it suitable only for topical use 2, 3
- The formulation maintains detectable local concentrations for up to 72 hours after application 9