Objective: To evaluate the safety and pharmacokinetic interaction between amprenavir (APV) and ritonavir (RTV).
Methods: Three open-label, randomized, two-sequence, multiple-dose studies having the same design (7 days of APV or RTV alone followed by 7 days of both drugs together) used 450 or 900 mg APV with 100 or 300 mg RTV every 12 h with pharmacokinetic assessments on days 7 and 14. Safety was monitored as clinical adverse events (AEs) and laboratory abnormalities.
Results: Relative to APV alone, RTV co-administration resulted in a 3.3- to 4-fold and 10.84 to 14.25-fold increase in the geometric least-square (GLS) mean area under the plasma concentration–time curve (AUCτ,ss) and minimum concentration (Cmin,ss), respectively. APV 900 mg with RTV 100 mg resulted in a 2.09-fold and 6.85-fold increase in the GLS mean AUCτ,ss and Cmin,ss, respectively. On day 14, the geometric mean (95% confidence interval) for 450 mg APV AUCτ,ss (μg • h/mL) was 23.49 (19.32–28.57) with 300 mg RTV and 35.42 (30.46–44.42) with 100 μg RTV, and for the 900 mg APV with 100 mg RTV 47.11 (39.47–61.24). The 450 mg APV Cmin,ss (μg/ml) were 1.32 (1.05–1.67) and 2.01 (1.70–2.61), and 2.47 (2.08–3.32) for 900 mg APV. The most common AEs were mild and included diarrhea, nausea/vomiting, oral parasthesias, and rash. The triglyceride and cholesterol increased significantly from RTV exposure.
Conclusion: Adding RTV to APV resulted in clinically and statistically significant increases in APV AUC and Cmin with variable effects on maximum concentration. The two RTV doses had similar effects on APV but AEs were more frequent with 300 mg RTV.