Disposition of diphenyl sulphoxide in rat

1. Radiolabelled diphenyl sulphoxide (U-14C- or 35S-) was administered by gavage (1.0 mmol/kg body weight) to the adult male Wistar rat following an overnight fast. 2. For both labelled forms faeces was the major route of excretion of radioactivity (50%) with substantial amounts still being voided during the third and fourth days (13%). Urinary elimination (42%) was similar during the first (20%) and second (17%) days and a small amount of radioactivity (7%) was found within the carcass after 4 days. 3. Plasma data showed a peak concentration at 40 min (tmax), a distribution half-life of 2 h (t1/2 alpha) and an elimination half-life of 22.5 h (t1/2 beta). Biliary studies revealed that 16% of the dose traversed the bile duct during the first day with nearly half of this being excreted in the first 8 h. 4. From urinary data, metabolism occurred via ring hydroxylation with subsequent conjugate formation. Oxidation of the sulphur to form the sulphone also took place. No evidence for sulphoxide reduction, cleavage of the ring structures or exclusion of the sulphur was obtained.