PIRNUOTM Cream (Mupirocin Cream USP, 2%) contains the dihydrate crystalline calcium hemi-salt of the RNA synthetase inhibitor antibacterial, mupirocin. Chemically, it is (αE,2S,3R,4R,5S)-5-[(2S,3S,4S,5S)-2,3-epoxy-5-hydroxy-4-methylhexyl]tetrahydro-3,4-dihydroxy-β-methyl-2H-pyran-2-crotonic acid, ester with 9-hydroxynonanoic acid, calcium salt (2:1), dihydrate.
The molecular formula of mupirocin calcium, USP is (C26H43O9)2Ca•2H2O, and the molecular weight is 1075.3 g/mol. The molecular weight of mupirocin free acid is 500.6 g/mol. The structural formula of mupirocin calcium, USP is:
Figure 1. Structure of Mupirocin Calcium, USP
PIRNUOTM Cream (Mupirocin Cream USP, 2%) is a white cream that contains 20 mg (2% w/w) of mupirocin equivalent to 21.5 mg (2.15% w/w) of mupirocin calcium, USP in an oil- and water-based emulsion. The inactive ingredients are benzyl alcohol, glycerol monostearate, mineral oil, phenoxyethanol, polyoxyl 20 cetostearyl ether, purified water and xanthan gum.