The Influence of Ritonavir, Alone and in Combination With Lopinavir, on Fenofibric Acid Pharmacokinetics in Healthy Volunteers

Background: \- Patients infected with the human immunodeficiency virus (HIV) are often treated with protease inhibitors that help fight HIV infection. However, these medications often increase blood cholesterol levels, particularly triglycerides and low-density lipoproteins, and can lead to heart disease and other problems. Patients may take drugs known as fibrates (such as gemfibrozil (Lopid )) to lower triglyceride levels, but even with maximum approved doses patients often cannot reach goal triglyceride levels. Research suggests that fibrates and certain HIV medications, such as ritonavir and lopinavir/ritonavir, may interact and decrease the effectiveness of the fibrate treatment. More research is needed to determine the best drug to lower triglyceride levels in HIV patients who are receiving protease inhibitor therapy. Objectives: \- To evaluate the drug-drug interaction between fenofibrate and protease inhibitors lopinavir/ritonavir and ritonavir. Eligibility: \- Healthy individuals between 18 and 60 years of age. Design: * This study will require a screening visit and 18 study visits. The screening visit will take 3 to 4 hours, and can occur 7 to 30 days before starting the study. The rest of the study, not including the screening visit, is 48 days. Three of the visits will take about 12 hours, and the remaining 15 visits will take about 1 hour. * For study days 1 to 7, participants will take fenofibrate alone. Participants will keep a daily record of medication doses and any side effects. * For study days 8 to 27, participants will take fenofibrate and ritonavir. Participants will keep a daily record of medication doses and any side effects. * For study days 29 to 48, participants will take fenofibrate and lopinavir/ritonavir. Participants will keep a daily record of medication doses and any side effects. * Participants will have regular study visits to provide blood samples for research and monitoring.