Ranitidine S-oxide is a metabolite of the histamine H₂receptor antagonist ranitidine .¹It is formedviaS-oxidation of ranitidine by flavin-containing monooxygenase 3 (FMO3) and FMO5.²Ranitidine S-oxide is acutely cytotoxic to the aquatic speciesB. calyciflorusandC. dubia(LC₅₀s = 4.51 and 7.85 mg/L, respectively), and it inhibits the reproduction ofB. calyciflorusandC. dubiawith chronic exposure (EC₅₀s = 0.83 and 0.51 mg/L, respectively).³It is mutagenic toS. typhimuriumand genotoxic toE. coliwhen used at concentrations ranging from 0.312 to 0.625 µg/ml and 0.312 to 5 µg/ml, respectively.

1.Smith, M.S., Oxford, J., and Evans, M.B.Improved method for the separation of ranitidine and its metabolites based on supercritical fluid chromatographyJ. Chromatogr. A.683(2)(1994) 2.Chung, W.-G., Park, C.-S., Roh, H.-K., et al.Oxidation of ranitidine by isozymes of flavin-containing monooxygenase and cytochrome P450Jpn. J. Pharmacol.84(2)213-220(2000) 3.Isidori, M., Parrella, A., Pistillo, P., et al.Effects of ranitidine and its photoderivatives in the aquatic environmentEnviron. Int.35(5)821-825(2009)