Retapamulin ointment, 1% is now approved by FDA as an antibacterial agent for the topical treatment of impetigo due to Staphylococcus aureus or Streptococcus pyogenes.
GLAXOSMITHKLINEAntibacterial agent approved for the topical treatment of impetigo caused by Staphylococcus aureus or Streptococcus pyogenes
This semisynthetic pleuromutilin antibiotic selectively inhibits bacterial protein synthesis by inhibiting peptidyl transfer, blocking P-site interactions, and preventing the normal formation of active 50S ribosomal subunits. This agent was approved on April 12, 2007, for the topical treatment of impetigo due to Staphylococcus aureus (methicillin-susceptible isolates only) or Streptococcus pyogenes in adults and in pediatric patients aged ≥9 months.
Efficacy. The efficacy of this agent was assessed in a double-blind, randomized, multicenter, parallel-group study in patients with impetigo affecting ≤100 cm2 total area or a total body surface area ≤2%. Patients enrolled in the study (N=210) were aged ≥9 months; the majority of enrolled patients (78%) were aged <13 years. Patients with any systemic signs and symptoms of infection and those with underlying skin disease or skin trauma with clinical evidence of secondary infection were excluded from the study. Enrolled patients were randomized to either retapamulin or placebo in a 2:1 ratio. The ointment was applied twice daily for 5 days. Clinically successful treatment was defined as treatment resulting in lesions that became dry without crusts and with or without erythema compared with baseline, treatment resulting in lesions that improved (decrease in size of affected area, number of lesions, or both) and no longer required antimicrobial therapy, or treatment resulting in an absence of lesions. Among patients who had satisfied the inclusion criteria and adhered to the protocol (the clinical per-protocol group), 89.5% of retapamulin-treated patients demonstrated clinical success versus 53.2% of placebo-treated patients at the end of therapy (2 days after treatment); at follow-up (9 days after treatment), 82.4% of retapamulin-treated patients demonstrated clinical success versus 43.1% of placebo-treated patients. An analysis of all patients who had a pathogen identified at study entry, satisfied the inclusion criteria, and adhered to the protocol (the bacteriological per-protocol group) demonstrated that retapamulin was effective against both S aureus (retapamulin, 89.8% clinical success at end of therapy and 84.5% clinical success at follow-up; placebo, 52.1% clinical success at end of therapy and 43.2% clinical success at follow-up) and S pyogenes (retapamulin, 90.6% clinical success at end of therapy and follow-up; placebo, 42.9% clinical success at end of therapy and 33.3% clinical success at follow-up).
Dosing. A thin layer of retapamulin should be applied to the affected area (adults, ≤100 cm2 in total body area; pediatric patients, ≤2% total body surface area) twice daily for 5 days.