Pharmacokinetic interaction between amprenavir/ritonavir and FosAmprenavir on cyclosporine in two patients with human immunodeficiency virus infection undergoing orthotopic liver transplantation

The pharmacokinetic interaction between highly active antiretroviral therapy (HAART) and immunosuppressive drugs is a critical element in the management of patients with human immunodeficiency virus infection who undergo orthotopic liver transplantation (OLT). We describe the effect of the coadministration of Amprenavir/Ritonavir (APV/r) and FosAmprenavir (FosAPV) on cyclosporine (CsA) concentrations in two patients receiving OLT for end-stage liver disease due to hepatitis C Virus. Patient 1, who was maintained on 300 mg CsA twice a day with a trough concentration (C-trough) around 250 ng/mL, restarted HAART 12 days after transplantation with 300 mg APV/r twice a day with corresponding APV C-trough of 5293 ng/mL and RTV C-tough of 186 ng/mL. Forty-eight hours after initiation of HAART, C-trogh of CsA was 1200 mg/mL, so it was necessary to reduce the CsA dosage 12-fold (50 mg every day) to achieve a therapeutic effect. In Patient 2, who was maintained on 300 mg CsA twice a day and a corresponding C-trough of 400 ng/mL, HAART was restarted 12 days post-OLT with FosAPV 1400 mg twice a day. After 48 hours C-trough of CsA was around 600 ng/mL and C-trough of FosAPV, 1221 ng/mL. In this case it was necessary to reduce the CsA administration 3.5-fold (175 mg every day). In conclusion, therapeutic drug monitoring was necessary to monitor HAART and CsA post-OLT to prevent toxicity due to both therapies. The use of FosAPV without ritonavir boostering is sufficient to maintain adequate CsA blood concentrations, avoiding any event of toxicity.