This is an open label single sequence single group non-randomized two way drug interaction study in healthy adult volunteers to determine the extent to which quinine, an inducer of cytochrome p450 CYP 3A4, affects the pharmacokinetics of midazolam, an accepted probe drug for CYP 3A4. The study will also determine the extent to which midazolam affects the pharmacokinetics of quinine. This will compare the pharmacokinetics of midazolam and quinine at baseline to their kinetics when they are taken together in 24 normal healthy adult volunteers who will serve as their own controls. All patients will be confined to the study site throughout the entire 11 day study period. On day 1 after a fast of at least 10 hours, all study participants will receive a single oral dose of midazolam 2 mg. Blood will be drawn at times sufficient to adequately define the baseline concentration time curve for midazolam and its metabolite, 1-hydroxy-midazolam. On the morning of day 4, after a 3 day washout period and following a fast of at least 10 hours, all volunteers will begin a regimen of 324 mg of quinine sulfate by mouth every 8 hours. All subjects will continue this regimen from day 4-10 (21 total doses). Blood will be drawn after the first daily dose of quinine on days 4 and 9 at times sufficient to adequately define the baseline and steady state concentration time curves for quinine. Additional blood will be drawn prior to the first daily dose of quinine on days 7,8,9,and 10. On day 10 after a fast of at least a 10 hours, all participants will receive both midazolam 2 mg and quinine 324 mg together. Blood will be drawn a times sufficient to characterize the pharmacokinetics of midazolam, 1-hydroxy-midazolam and quinine under the stated conditions.