<qa>  What is the dose of aprepitant measured at specified time points?This two part study will determine the appropriate dosing regimen of aprepitant for the prevention of postoperative nausea and vomiting PONV in pediatric participants 6 months to 17 years of age, by assessing pharmacokinetic parameters and monitoring safety and tolerability of administered doses. Part I will be an open label investigation of a single dose of aprepitant measuring pharmacokinetics at specified time points up to 48 hours after aprepitant dosing. Part II will be a double blind trial of participants randomized to receive either aprepitant or ondansetron. 