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.