Relative bioavailability of an extemporaneous ondansetron 4-mg capsule formulation versus solution

To compare the relative bioavailability of an extemporaneous ondansetron capsule formulation with that of an identical dose of the commercially available solution formulation.

Open-label, randomized, two-way crossover study.

University-affiliated research laboratory.

Sixteen (eight men, eight women) healthy, nonsmoking volunteers.

Participants were randomly assigned to receive a 4-mg dose of either the commercially available ondansetron solution or the extemporaneous ondansetron capsule formulation. Blood sampling was performed over 12 hours after dosing. After a washout period of at least 3 days, each participant was switched to the alternate formulation, and blood sampling was repeated.

Ondansetron was well absorbed after administration of both formulations, with the solution achieving a faster rate of drug absorption over the first hour of dosing. After the peak plasma concentration was achieved, the plasma concentration-time curves of both formulations declined at a similar steady rate. There were no significant differences in pharmacokinetic parameters between the two formulations, and the relative bioavailability of the capsule versus the solution formulation was 101%.

Similar concentration-time curves and pharmacokinetic parameters were achieved with the two formulations. The commercially available solution would be a useful alternative formulation for administration of low-dose ondansetron in research and clinical settings.