Darunavir/r increases exposure to nevirapine
Dailly and colleagues used data from a TDM program and a population PK approach to examine the influence of coadministered drugs on nevirapine pharmacokinetics. The cohort was small (51 patients) but in the final one compartment model there was relationship between nevirapine clearance and the presence of darunavir in the regimen.
In summary, there was a significant decrease in clearance (CL/f, 3.84 ± 0.92 vs 2.76 ± 1.00 L/h) and an increase in the mean nevirapine trough plasma concentrations (3.68 ± 1.69 vs 5.35 ± 3.20 mg/L) in combination with darunavir.
The limitations of the study are that it is TDM data and small numbers. The advantage is that these are results obtained with the recommended twice daily dose of darunavir/ritonavir (600/100 mg) rather than the lower doses (300/100 or 400/100 mg) used in the early interaction studies.
Source: www.hiv-druginteractions.org (July 2009)
Dailly E et al. Influence of darunavir coadministration on nevirapine pharmacokinetics in HIV-infected patients: a population approach. HIV Med, 2009, epub ahead of print.