Pharmacokinetic interaction between nevirapine and nortriptyline in rats: inhibition of nevirapine metabolism by nortriptyline

One of the most frequent comorbidities of HIV infection is depression, with a lifetime prevalence of 22 to 45%. Therefore, it was decided to study a potential pharmacokinetic interaction between the nonnucleoside reverse transcriptase inhibitor nevirapine (NVP) and the tricyclic antidepressant nortriptyline (NT). NVP and NT were administered to rats either orally, intraduodenally, or intravenously, and the changes in plasma levels and pharmacokinetic parameters were analyzed. Experiments with rat and human hepatic microsomes were carried out to evaluate the inhibitory effects of NT on NVP metabolism. NVP plasma concentrations were significantly higher when this drug was coadministered with NT. The maximum plasma concentrations of NVP were increased 2 to 5 times and the total plasma clearance was decreased 7-fold in the presence of NT. However, statistically significant differences in the pharmacokinetic parameters of NT in the absence and presence of NVP were not found. In vitro studies with rat and human hepatic microsomes confirmed the inhibition of NVP hepatic metabolism by NT in a concentration-dependent way, with the inhibition being more intense in the case of rat microsomes. In conclusion, a pharmacokinetic interaction between NVP and NT was detected. This interaction was a consequence of the inhibition of hepatic metabolism of NVP by NT. In vivo human studies are required to evaluate the effects of this interaction on the pharmacokinetics of NVP before it can be taken into account for patients receiving NVP.

Safety and Efficacy of Once-Daily Didanosine, Tenofovir and Nevirapine as a Simplification Antiretroviral Approach

Objective

To assess the efficacy and safety of a once-daily antiretroviral regimen in HAART-experienced subjects with long-lasting viral suppression.

Methods

One-hundred-and-sixty-nine patients with chronically suppressed viral load (limit of detection <50 copies/ml) were recruited. Based on patient willingness to simplify treatment, 84 of them continued receiving their usual treatment (BID Group) and 85 switched to once-daily didanosine/tenofovir/nevirapine (QD Group) in a non-randomized fashion.

Results

At week 48, the proportion of patients with viral suppression in the QD and in the BID Group, respectively, was 97 vs 100% in the per-protocol analysis ( P=0.497), and 76 vs 86% for the intention-to-treat analysis ( P=0.176). Nevertheless, CD4 count decreased in the QD Group, with a mean decline of 95 cells/mm3 (95% CI: 45–145). Twelve subjects in the QD Group (14%) discontinued treatment due to adverse events, mainly nevirapine-related hepatitis (6%). No significant differences regarding the rate of acute pancreatitis or peripheral neuropathy were observed between both groups. A significant improvement in the lipid profile was only seen in the QD Group. High levels of adherence were observed in both groups during follow-up, as well as a good quality of life. At week 48, a reduction in effort to take medication ( P≤0.001) and an increment in the satisfaction with the treatment ( P<0.001) was only seen in the QD group. No differences were observed in median nevirapine trough levels between patients on twice-daily nevirapine at baseline (4820 ng/ml) and subjects in the QD Group (6090 ng/ml, P=0.30).

Conclusion

Treatment simplification to a once-daily antiretroviral regimen based on didanosine, tenofovir and nevirapine may be a valid approach in HIV-infected subjects with long-lasting viral suppression. Combination of standard doses of didanosine and tenofovir may have contributed to the CD4 cell decline observed with this QD regimen.