Evaluation of Potential Pharmacokinetic Interactions Between HIV Protease Inhibitors and Calcium Channel Blockers

Ischemic cardiovascular disease and hypertension occur in persons with HIV infection, and the incidence and prevalence may increase over time as the infected population ages. Standard pharmacologic interventions for these illnesses often include calcium channel blockers (CCBs). Many of the calcium channel blockers are metabolized by cytochrome P450 3A4 (CYP 3A4), which is inhibited by some protease inhibitors (PIs). Thus, there is potential for clinically significant interactions between CCBs and PIs. The presence of significant drug-drug interactions may influence the dosing, monitoring, and choosing of CCBs and/or PIs when used in persons with HIV infection. Because of the potential concomitant use of CCBs with the PI combination IDV/RTV, this study will evaluate bi-directional drug-drug interactions between 2 commonly used CCBs and IDV/RTV. This information should assist clinicians in choosing the appropriate CCBs to treat hypertension or cardiovascular disease in persons taking PIs.

Patients are randomized to 1 of the following 2 arms:

Arm A: diltiazem CD interaction with IDV and RTV. Arm B: amlodipine interaction with IDV and RTV. From Days 1 to 7, patients take diltiazem CD (Arm A) or amlodipine (Arm B). Plasma is collected for PK over a 24-hour period beginning on Day 7. From Days 8 to 19, patients stop taking their assigned CCB and take IDV and RTV. Plasma is collected for PK over a 12-hour period on Day 19. From Days 20 to 26, patients continue to take IDV and RTV and add diltiazem CD (Arm A) or amlodipine (Arm B). Patients stop all 3 drugs after the last dose on Day 26. Plasma is collected for PK for a 24-hour period beginning on Day 26. Blood work, liver and kidney function tests, urinalysis, and an electrocardiogram (EKG) are performed at some visits.