Impetigo ointment is first in new class

Children with impetigo will be among those who will benefit from using retapamulin (Altabax 1%, GlaxoSmithKline). This topical ointment is one of a new class of antibacterials known as the pleuromutilins, recently approved by the Food & Drug Administration. The agent is indicated for treating impetigo caused by methicillin-susceptible Staphylococcus aureus or Streptococcus pyogenes in patients nine months of age or older.

The way retapamulin works is by selectively inhibiting bacterial protein synthesis by interacting at a site on the 50S subunit of the bacterial ribosome. By binding at this location, the drug inhibits peptidyl transfer, blocks P-site interactions, and prevents the normal formation of active 50S ribosomal subunits. In vitro, the active ingredient has shown no target-specific cross-resistance to other established classes of antibacterials. This, according to GSK, is most likely due to the fact that no other antibacterials use the same specific mode of action.

No more that 100 cm² in total area should be covered by the ointment in adults and no greater than 2% of total body surface area in pediatric patients, according to GSK. Once the oinment is applied, the affected area may be covered with a sterile bandage or gauze dressing, which may be helpful for infants and young children who might accidentally touch or lick the lesion.

In reviewing the new topical, the FDA evaluated the results of a randomized, placebo-controlled, multi-center phase III study examining the efficacy of retapamulin in 210 adults and children with impetigo infection. Following five days of treatment, the rates of successful treatment were 85.6% in the retapamulin group versus 52.1% for placebo. Microbiological efficacy was also evaluated and rates of successful treatment were 91.2% and 50.9% for retapamulin and placebo, respectively. The most common drug-related adverse event during the clinical trial was application-site irritation (≤ 2%). If local irritation occurs, the manufacturer recommends that the ointment be wiped off and an alternative therapy initiated.

According to GSK, pharmacists need to remind patients that retapamulin should be used for the full time recommended by the prescriber even if symptoms appear to improve. If no improvement in symptoms is seen within three to four days, patients should notify their healthcare provider.

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