A One-Directional, Open-Label Drug-Food Interaction Study to Investigate the Effects of Multiple-Daily Consumptions of Grapefruit Juice on the Single-Dose Pharmacokinetics of Colchicine in Healthy Volunteers

Grapefruit juice is an inhibitor of the cytochrome P450 (CYP) 3A4 enzyme system, one of the enzyme systems responsible for the metabolism of colchicine. This study will evaluate the effect of multiple daily consumptions of grapefruit juice on the pharmacokinetic profile of a single 0.6 mg dose of colchicine. On study Day 1, after a fast of at least 10 hours twenty-two healthy, non-smoking, non-obese, non-pregnant adult volunteers between the ages of 18 and 45 will be given one dose of colchicine (1 x 0.6 mg tablet). Fasting will continue for 4 hours after the dose. Blood samples will be drawn from all participants before dosing and for 24 hours post-dose on a confined basis at times sufficient to adequately define the pharmacokinetics of colchicine. Blood sampling will continue on a non-confined basis on Days 2-5. After a 14 day washout period, starting on the morning of Day 15 and continuing through Day 17, subjects will return to the clinic for consumption of an administered dose of grapefruit juice (1 x 240 ml) twice daily. On the morning of Day 18 after a fast of at least 10 hours all subjects will receive a co-administered single oral dose of colchicine (1 x 0.6 mg) and grapefruit juice (1 x 240 ml). Fasting will continue for 4 hours after the dose. Blood samples will be drawn from all participants before dosing and for 24 hours post-dose on a confined basis at times sufficient to adequately define the pharmacokinetics of colchicine in the presence of grapefruit juice. Blood sampling will continue on a non-confined basis on Days 19-22. Subjects will consume the final administered dose of grapefruit juice (1 x 240 ml) in the evening on Day 18. A further goal of this study is to evaluate the safety and tolerability of this regimen in healthy volunteers. Subjects will be monitored throughout participation in the study for adverse reactions to the study drug and/or procedures. Seated blood pressure and pulse will be measured prior to dosing and at approximately 1, 2, and 3 hours following drug administration on Days 1 and 18 to coincide with peak plasma concentrations of colchicine. All adverse events whether elicited by query, spontaneously reported, or observed by clinic staff will be evaluated by the Investigator and reported in the subject's case report form.