Pgp Transporter and CNS Biodistribution of Ondansetron in Healthy Volunteers

The study hypothesis is that inhibition of Pgp efflux transporters will increase the CNS bio-distribution of the 5-HT3R antagonist ondansetron. Specifically: 1. Intravenous administration of ondansetron is expected to yield low CSF exposure. 2. Co-administration of ondansetron with intravenous tariquidar, an inhibitor of Pgp efflux transporters, will result in increased CSF exposure of ondansetron.