Ritonavir is a potent inhibitor of CYP3A4, one of the enzymes responsible for the metabolism of colchicine. This study will evaluate the effect of multiple doses of ritonavir on the pharmacokinetic profile of a single 0.6 mg dose of colchicine. A secondary objective is to evaluate the safety and tolerability of this regimen in healthy volunteers. All study subjects will be monitored for adverse events throughout the study period.