Visit 1: Participants will be randomized to one of three treatment possibilities: 1) phenytoin with megestrol, 2) placebo with megestrol, 3) placebo with placebo. Participants will receive phenytoin (200 mg BID) or placebo and will be instructed to take this medication for one full day (two doses) before starting their megestrol. They will take this medication for a total of 3.5 days.