Bioequivalence and Bioavailability Forum

Hello Everyone,

Sulindac sulfoxide is a prodrug with no pharmacological activity. It is water-soluble and readily absorbed from the intestine then undergoes two major biotransformation reactions: a reversible reduction into a Sulfide which is pharmacologically active and an irreversible oxidation into a Sulfone.

My question is, in a bioequivalence study comparing sulindac tablet formulations, which analytes will the 90% CI be based on; the parent compound and the sulfide (active metabolite) or the sulfide only or the parent compound only? I couldn’t find an FDA guidance paper for sulindac.