Related Experiment Video
Updated: Aug 7, 2026

Quantitative Structure-Activity Relationship, Activity Prediction, and Molecular Dynamics of Non-nucleotide Reverse Transcriptase Inhibitors
Published on: May 9, 2025
[Clinical and pharmacokinetic interactions between methadone and nelfinavir (Nemesia study)]
Andrés Marco1, Elisabet Deig, Josep Cadafalch
1Programa VIH/SIDA, CP La Modelo, Barcelona, Spain.
Background And Objective:
Patients on methadone maintenance therapy who are administered nelfinavir show a decrease in methadone plasma levels. However, the clinical relevance of this fact is seldom significant because it does not correlate with the appearance of opioid withdrawal symptoms (OWS). The objective of this study was to assess the clinical and pharmacokinetic interactions between methadone and nelfinavir.
Patients And Method:
A prospective multicenter study of human immunodeficiency virus (HIV) positive patients on stable methadone therapy who initiated nelfinavir was performed. To determine the presence of OWS, 2 questionnaires, objective and subjective, were administered at weeks 1, 2, 3 and 4. A pharmacokinetic study measuring the minimal plasmatic concentration of methadone was done at baseline and at week 4.
Results:
29 patient were included. In 7 patients who underwent pharmacokinetic studies, the minimal plasmatic concentration of methadone decreased after 4 weeks of nelfinavir treatment from 6.889 ng/ml to 4.354 ng/ml (37%; p = 0.046). However the results of the questionnaires did not show the significant OWS, which precluded an increase in the dose of methadone.
Conclusions:
In patients under stable methadone treatment, antiretroviral therapy including nelfinavir does not require any significant modification of methadone dose. The decrease in methadone plasmatic levels does not correlate with OWS.
More Related Videos
Related Concept Videos
Pharmacokinetics: Drug–Food and Drug–Viral Interactions
Pharmacokinetics: Drug–Drug Interactions
Effect of Hepatic Disease on Pharmacokinetics: Dose Adjustments Due to Hepatic Impairment
Drug toxicity: Drug–Drug Interaction
Pharmacokinetics in Pediatric Patients: Drug Excretion
Effect of Hepatic Disease on Pharmacokinetics: Active Drug, Metabolite and Fraction of Metabolized Drug

