On Day 19 after a fast of at least 10 hours, all study participants will receive 300mg theophylline (80mg/15ml) and 0.6 mg colchicine (1 x 0.6mg tablet) together. Fasting will continue for 4 hours following these co-administered doses. All subjects will be confined to the clinic for dosing and the following 24-hour period. Blood samples will be drawn at times sufficient to adequately determine the pharmacokinetics of theophylline in the presence of colchicine at steady state. Blood sampling will continue on a non-confined basis on Days 20-21. The final dose of colchicine (1x0.6mg) will be administered to subjects the evening of Day 19.