Pharmacokinetic Evaluation of Fosamprenavir and Kaletra Coadministration
Robert DiCenzo, Pharm.D.
Department of Pharmacy Practice
School of Pharmacy and Pharmaceutical Sciences
University at Buffalo
E-mail: robert_dicenzo@urmc.rochester.edu
Subjects enrolled in AACTG 5143 were randomized to receive fosamprenavir/r
(700/100) mg BID, LPV/r 400/100 mg BID, or fosamprenavir 700 mg with LPV/r
400/100 mg BID with tenofovir plus 1-2 NRTIs. Kashuba et al compared the
steady state pharmacokinetics of each study drug at weeks 2-4. Reported
results included the following:
Geometric Mean Ratio (Upper 99.9% CI)
p-value
Amprenavir AUC
0.36 (0.64)
< 0.0001
Amprenavir C12h
0.31 (0.61)
< 0.0001
LPV AUC
0.52 (0.89)
0.0001
LPV C12h
0.39 (0.98)
0.0008
Both fosamprenavir and LPV exposures were significantly reduced during
coadministration, which was not accounted for by tenofovir use. The authors
concluded that lower drug exposure could potentially lead to treatment
failure; therefore, enrollment in AACTG 5143 was suspended.
Kashuba, A., C. Teirney, et al. (2003). Combining GW433908 (fosamprenavir; 908)
with lopinavir/ritonavir (LPV/R) in HIV-1 infected adults results in substantial
reductions in amprenavir (APV) and LPV concentrations: Pharmacokinetic (PK)
results from Adult ACTG Protocol A5143. 43rd Annual International Conference
on Antimicrobial Agents and Chemotherapy, Chicago, IL.
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