Pharmacokinetics of three formulations of ondansetron hydrochloride in healthy volunteers: 24-mg oral tablet, rectal suppository, and i.v. infusion

The absolute bioavailability and pharmacokinetics of three formulations of ondansetron hydrochloride 24 mgan oral tablet, an intravenous solution, and an extemporaneous rectal suppositorywere studied. Twelve healthy, nonsmoking volunteers (six men and six women) were given ondansetron in a study with a three-way crossover design. All subjects received each dosage form on the same day in the following order: Oral tablet, rectal suppository, and intravenous infusion. Administrations were separated by one week. Blood sampling times varied, depending on the administration route. Mean absolute bioavailability for the oral tablet and the rectal suppository differed significantly. Absorption of ondansetron was prolonged when it was administered as the rectal suppository. Absolute bioavailability for the 24-mg tablet was similar to that for other tablet strengths in previous studies. All subjects completed the study without significant adverse effects. Absorption of ondansetron from the rectal suppository was prolonged compared with the oral tablet and the i.v., infusion. Bioavailability for the 24-mg suppository formulation was considerably lower than for the 24-mg tablet.