Drop in trough blood concentrations of tacrolimus after switching from nelfinavir to fosamprenavir in four HIV-infected liver transplant patients

Author:

Pea Federico1,Tavio Marcello2,Pavan Federica1,Londero Angela2,Bresadola Vittorio3,Adani Gian Luigi3,Furlanut Mario1,Viale Pierluigi2

Affiliation:

1. Institute of Clinical Pharmacology & Toxicology, Department of Experimental and Clinical Pathology and Medicine, Medical School, University of Udine, Udine, Italy

2. Clinic of Infectious Diseases, Department of Medical and Morphological Research, Medical School, University of Udine, Udine, Italy

3. Department of Surgery and Transplantation, Medical School, University of Udine, Udine, Italy

Abstract

Solid organ transplantation in HIV-infected individuals requires concomitant use of immunosuppressants and antiretrovirals that may cause significant drug interactions. Here we report on a peculiar pharmacokinetic interaction between tacrolimus and protease inhibitors (PIs) which occurred in four HIV-infected liver transplant patients who had to shift PI therapy from nelfnavir to fosamprenavir as a consequence of regulatory restrictions. After the switch, tacrolimus trough blood concentrations significantly dropped in all patients (mean ±sd 6.9 ±2.6 versus 3.2 ±2.0 ng/ml before and after the switch, respectively; P=0.01), so that a marked dosage increase was needed (0.29 ±0.14 versus 0.88 ±0.48 mg/day, 1–3 days before and 3 weeks after the switch, respectively; P=0.046) to attain the desired target (8.7 ±2.3 ng/ ml). Consistently, marked changes of the concentration/dose ratio of tacrolimus were observed in all cases (27.2 ±9.7 ng/ml per mg/kg/day versus 9.7 ±4.0 ng/ml per mg/kg/day before and after the switch, respectively; P<0.001). Our findings suggest that fosamprenavir may be less potent than nelfinavir in inhibiting tacrolimus clearance and support the need for higher tacrolimus dosage to avoid insufficient immunosuppression in HIV-infected liver transplant patients when switching from nelfinavir to fosamprenavir or even when directly starting antiretroviral therapy with fosamprenavir.

Publisher

SAGE Publications

Subject

Infectious Diseases,Pharmacology (medical),Pharmacology

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