Retapamulin is a novel semisynthetic pleuromutilin antibiotic specifically 
designed for use as a topical agent. The unique mode of action by which 
retapamulin selectively inhibits bacterial protein synthesis differentiates it 
from other nonpleuromutilin antibacterial agents that target the ribosome or 
ribosomal factors, minimizing the potential for target-specific cross-resistance 
with other antibacterial classes in current use. In vitro studies show that 
retapamulin has high potency against the Gram-positive bacteria (Staphylococcus 
aureus, Streptococcus pyogenes, and coagulase-negative staphylococci) commonly 
found in skin and skin-structure infections (SSSIs), including S. aureus strains 
with resistance to agents such as macrolides, fusidic acid, or mupirocin, and 
other less common organisms associated with SSSIs, anaerobes, and common 
respiratory tract pathogens. Clinical studies have shown that twice-daily 
topical retapamulin for 5 days is comparable to 10 days of oral cephalexin in 
the treatment of secondarily infected traumatic lesions. A 1% concentration of 
retapamulin ointment has been approved for clinical use as an easily applied 
treatment with a short, convenient dosing regimen for impetigo. Given the novel 
mode of action, low potential for cross-resistance with established 
antibacterial agents, and high in vitro potency against many bacterial pathogens 
commonly recovered from SSSIs, retapamulin is a valuable enhancement over 
existing therapeutic options.