• The 90% confidence interval of ratios of least-squares means for the Ln transformed kinetic parameters AUC 0-t , AUCinf , & Cmax of quinine before and after a single dose of theophylline and of theophylline before and after quinine at steady state [ Time Frame: days 1 & 12 ] [ Designated as safety issue: Yes ]
  

• All treatment emergent adverse events that occur during the observation period, their date of onset, severity rating ,and an a classification of of causality [ Time Frame: days 1-12 ] [ Designated as safety issue: Yes ]
  

This study will compare the pharmacokinetics of theophylline alone and in the presence of quinine sulfate at steady state. In this non-blinded crossover study 24 normal healthy, non-smoking, non-obese male volunteers will serve as their own controls in two cohorts of 12 volunteers each. On day 1 after a minimum overnight fast of 10 hours, study participants will receive a single oral dose theophylline 300mg. Blood will be drawn at times sufficient to adequately define the baseline concentration time curve for this drug. After a 3 day washout period the 12 volunteers will begin a 7 day course of quinine sulfate 648 mg every 8 hours. If ≥ 62.5% of the volunteers in cohort one do not tolerate the 648mg dose of quinine sulfate, the second cohort of 12 volunteers will receive 324mg doses according to the originally stated dosing regimen. On day 11 blood will be drawn from volunteers in both cohorts sufficient to adequately characterize the steady state kinetics of quinine sulfate. On the morning of day 12 after a fast of at least 10 hours the volunteers will receive both quinine sulfate 648mg and theophylline 300mg. In both cohorts blood will be drawn at times sufficient to adequately define the concentration time curve for both a single dose theophylline in the presence of quinine sulfate at steady state and steady state quinine in the presence of theophylline. The concentration time curves generated will be compared to determine the extent of the drug drug interactions.