Toxicokinetics and lack of uterotropic effect of orally administered S-equol

► Oral S-equol was rapidly absorbed in rat and monkey with AUC linear vs. dose. ► Unconjugated S-equol in plasma was typically less than 1% of drug-related material. ► Orally dosed S-equol showed minimal induction or inhibition of cytochrome P450. ► S-equol was highly protein bound (>95%) in plasma from rat, monkey and man. ► S-equol had no effect on uterine weight or morphology after high repeat oral dosing.