Pharmacology Update
Retapamulin Ointment (Altabax™)
By William T. Elliott, MD, FACP, and James Chan, PharmD, PhD, Dr. Elliott is Chair, Formulary Committee, Northern California Kaiser Permanente; Assistant Clinical Professor of Medicine, University of California, San Francisco; Dr. Chan is Pharmacy Quality and Outcomes Manager, Kaiser Permanente, Oakland, CA. Drs. Chan and Elliott report no financial relationship to this field of study.
The FDA has approved the first of a new class of antibiotics for the topical treatment of impetigo. Retapamulin belongs to a class of agents called pleuromutilins. It is marketed by GlaxoSmithKline as Altabax.
Indications
Retapamulin is indicated for the topical treatment of impetigo due to Staphylococcus aureus (methicillin--susceptible only) or Streptococcus pyogenes in patients 9 years of age or older.1
Dosage
A thin layer is applied to the affected are twice daily for 5 days. It may be applied to an area up to 100 cm2 or 2% of total body surface.1
Retapamulin is supplied as 10 mg/ g of ointment and in 5, 10, and 15 gram tubes.
Potential Advantages
In vitro studies suggest a low potential for development of resistance against S. aureus and S. pyogenes.2 Potent activity has been shown against S. aureus and beta-hemolytic streptococci. Cross-resistance has not been observed in microorganisms resistant to oxacillin, erythromycin, or mupirocin.3 Retapamulin is applied twice daily for 5 days compared to 3 times a day for 5 days for mupirocin ointment.
Potential Disadvantages
Retapamulin is bacteriostatic not bacteriocidal at the minimum inhibitory concentrations. Even though it demonstrates in vitro activity against methicillin-resistant S. aureus, it is not indicated for these microorganisms as in vitro susceptibility was not correlated with clinical success.1
Comments
Retapamulin is a topical, semisynthetic, antibiotic from a new class of antibiotics, the pleuromutilins. Its efficacy was shown in a double-blind, placebo-controlled study involving adult and pediatric patients with impetigo (n = 210). The majority of the patients were less than 13 years of age. Patients were randomized to retapamulin applied twice daily for 5 days or placebo applied in the same manner. Clinical success (2 days after therapy) was defined as the absence of treated lesions, or treated lesions had become dry without crusts with or without erythema compare to baseline, or had improved such that no further antimicrobial therapy was required. In the clinical intent-to-treat (ITT) population, success rate was 85.6% compared to 52.1% for placebo at the end of treatment.1 For those with microorganism identified at study entry, ITT success was 88.6% and 49,1% respectively. In a similarly designed study in patients with secondarily infected dermatitis, retapamulin was reported to be non-inferior to cephalexin (500 mg twice daily for 10 days).4 Clinical success in the intent-to-treat population was 82.9% for retapamulin and 86.3% for cephalexin. The difference was -3.4% (95% CI, -9.7, 2.9). The lower limit for noninferiority was set as -10%. Retapamulin is well tolerated with application site reaction reported is less than 2% of patients.1 Patients in this study indicated a preference for topical application over systemic therapy. Comparative studies to other topical agents such as mupirocin has not been published. The cost for 15 g of retapamulin is $68 compared to $50 for 22 g of mupirocin.
Clinical Implications
Topical therapy is generally preferable for the treatment of impetigo.5-6 Currently products include mupirocin and fusidic acid. The latter is not available in the US and resistance to mupirocin as been reported in Europe and the United States.7 Retapamulin provides a new topical agent for the treatment of impetigo and represents an important new option for this indication. Topical application and short course of therapy are attractive characteristics.
References
1. Altabax Product Information. GlaxoSmithKline. April 2007.
2. Kosowski-Shick K, et al. Antimicrob Agents Chemother. 2006;50:765-769.
3. Jones RN, et al. Antimicrob Agents Chemother. 2006;50:2583-6.
4. Parish LC, et al. J Am Acad Dermatol. 2006;55:1003-1013.
5. Cole C, Gazewood J. Am Fam Physician. 2007;75:859-864.
6. Koning S, et al. Cochrane Database Syst Rev. 2004;(2):CD003261.
7. Deshpande LM, et al. Diagn Microbiol Infect Dis. 2002;42:283-290.
The FDA has approved the first of a new class of antibiotics for the topical treatment of impetigo. Retapamulin belongs to a class of agents called pleuromutilins.You have reached your article limit for the month. Subscribe now to access this article plus other member-only content.
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