In early April 2007, the Food and Drug Administration approved a new topical antibiotic, retapamulin ointment 1%, (Altabax), for the treatment of impetigo. Manufactured by GlaxoSmithKline, it is the first antibiotic in the new pleuromutilin drug class.
Indications
Altabax is indicated solely for the treatment of impetigo in patients 9 months of age or older. The topical antibiotic is currently indicated for methicillin-susceptible Staphylococcus aureus and Streptococcus pyogenes, although preliminary data suggests that it may be effective against methicillin-, mupirocin-, and fusidic acid-resistant strains of S. aureus.1
Mechanism of Action
Altabax is a semisynthetic derivative of pleuromutilin, a naturally occurring substance found in mushrooms. The drug is bacteriostatic, and selectively inhibits protein synthesis at the site of the 50S subunit in the bacterial ribosome.2
Drug Metabolism
Systemic exposure to Altabax is minimal since it is applied topically. The drug that is absorbed is metabolized by the liver's cytochrome P450 3A4 microsomes. Coadministration of Altabax and oral ketoconazole produced an increased serum concentration of Altabax. However, due to Altabax's low systemic exposure, dosage adjustments are unnecessary when coadministered with CYP43A4 inhibitors such as ketoconazole.2 Altabax is also unlikely to affect the metabolism of other P450 substrates.
Contraindications
Altabax does not have any known contraindications. The ointment is a pregnancy Category B and has been tested in pediatric (as young as 9 months), adult, and geriatric patients without incident. However, the use of Altabax has not been tested in nursing mothers. Therefore, it is unknown if the drug is excreted through breast milk.
Adverse Reactions
Clinical trials with Altabax included over 2,000 adult and pediatric patients. The most frequently reported adverse event was application site irritation which occurred in approximately 1.5% of the treatment groups. Other reported adverse events were statistically nonsignificant compared to the control and placebo groups. Patients that develop signs of skin sensitivity or severe local irritation should discontinue use.
Dosage and Administration
Altabax is available in 5, 10, and 15 gram tubes with a concentration of 10 mg retapamulin/1 gram of ointment. A thin film of the ointment is applied directly to the site of skin infection twice a day for 5 days. The maximum area of coverage should be 100 cm2 or less in adults or 2% of the total body area in pediatric patients.2 Patients may apply sterile gauze or a bandage over the treated area without changing the efficacy of the drug. Altabax should not be ingested and is not for ophthalmic, oral, intranasal, or vaginal use.2
Additional Information
Altabax should only be used in skin infections in which susceptible organisms have been identified or strongly suspected. Although costs vary, the drug sells for approximately $43 (5 gram tube) to $88 (15 gram tube).3 Generally, patients will not need any more than a 5 gram tube for the typical treatment regimen.
Mupirocin (Bactroban) is the only other approved topical antibiotic used in the United States for the treatment of impetigo. Mupirocin is generally prescribed as three times a day for 12 days. Advantages of Altabax over mupirocin include a less frequent dosing schedule, shorter treatment course, and lower cost.1
Patients should be instructed to use a clean cotton swab to apply the ointment, wash their hands immediately after application, and store the ointment at room temperature. Patients should also tell their provider if no improvement in symptoms is noticed after 3 to 4 days of use.
REFERENCES