Retapamulin is a topical antibiotic developed by GlaxoSmithKline. It is the first drug in the new class of pleuromutilin antibiotics to be approved for human use. It is marketed as an ointment under the brand names Altabax and Altargo. Retapamulin was approved by the United States Food and Drug Administration in April 2007 for the treatment of bacterial skin infections such as impetigo. In May 2007, retapamulin received approval in the EU from the European Medicines Agency for the same indication. Clinical trials have demonstrated its efficacy against certain Gram-positive bacteria including MRSA. Indications
Retapamulin is indicated for the topical treatment of impetigo due to Staphylococcus aureus (methicillin-susceptible only) or Streptococcus pyogenes. Pharmacology
Mechanism of action
Retapamulin is an antibacterial agent, specifically a protein synthesis inhibitor. The medication selectively inhibits bacterial protein synthesis by interacting at a site on the 50S subunit of the bacterial ribosome through an interaction that differs from other antibiotics. Pharmacokinetics
Systemic exposure following topical application through intact skin is low. Contraindications
None yet reported. Adverse reactions
The most common reported adverse reaction was irritation at the application site. == References ==
These and other novel genes (dptI, dptJ) are believed to be involved in supplying the nonproteinogenic amino acids L-3-methylglutamic acid and Kyn; they are located next to the NRPS genes.The decanoic acid portion of daptomycin is synthesized by fatty acid synthase machinery (Figure 2). Post-translational modification of the apo-acyl carrier protein (ACP, thiolation, or T domain) by a phosphopantetheinyltransferase (PPTase) enzyme catalyzes the transfer of a flexible phosphopantetheine arm from coenzyme A to a conserved serine in the ACP domain through a phosphodiester linkage. The holo-ACP can provide a thiol on which the substrate and acyl chains are covalently bound during chain elongations. The two core catalytic domains are an acyltransferase (AT) and a ketosynthase (KS). The AT acts upon a malonyl-CoA substrate and transfers an acyl group to the thiol of the ACP domain. This net transthiolation is an energy-neutral step. Next, the acyl-S-ACP gets transthiolated to a conserved cysteine on the KS; the KS decarboxylates the downstream malonyl-S-ACP and forms a β-ketoacyl-S-ACP. This serves as the substrate for the next cycle of elongation. Before the next cycle begins, however, the β-keto group undergoes reduction to the corresponding alcohol catalyzed by a ketoreductase domain, followed by dehydration to the olefin catalyzed by a dehydratase domain, and finally reduction to the methylene catalyzed by an enoylreductase domain. Each KS catalytic cycle results in the net addition of two carbons.