Mupirocin (BRL-4910A) is an orally active antibiotic isolated from Pseudomonas fluorescens. Mupirocin (BRL-4910A) apparently exerts its antimicrobial activity by reversibly inhibiting isoleucyl-transfer RNA, thereby inhibiting bacterial protein and RNA synthesis^[1][2]. In Vitro: Mupirocin (BRL-4910A) shows a high level of activity against staphylococci and streptococci and against certain gram-negative bacteria. Mupirocin (BRL-4910A) is highly bound (95% bound) to the protein of human serum, and activity was reduced 10- to 20-fold in the presence of human serum^[1]. In Vivo: Mupirocin is well absorbed after oral and parenteral administration but serum antibiotic concentrations were short-lived as a result of extensive degradation to the antibacterially inactive metabolite, monic acid A^[1].