Monitoring drug levels of nevirapine in the blood and providing this information to doctors and patients has not resulted in improved treatment outcomes for Dutch patients, according to a report in the June 1st edition of the Journal of Acquired Immune Deficiency Syndromes.
Dutch researchers looked at 45 patients receiving nevirapine within the ATHENA study, a national observational cohort. They compared treatment outcomes, toxicity and pharmacokinetics in 24 patients who received results of therapeutic drug monitoring tests, and a control group of 21 patients who underwent therapeutic drug monitoring without receiving the results.
Blood was sampled four and 12 weeks after starting treatment, and then every 12 weeks. Researchers compared rates of treatment discontinuation and the proportion of patients with viral load below 500 copies/ml.
Although significantly less variation in nevirapine concentration was noted over time in the unblinded TDM group (p=0.02), there was no difference after 24 months between the groups in the proportion who had discontinued nevirapine treatment (21% vs 19%), in the time to nevirapine discontinuation nor in the proportions with viral load below 500 copies at months 6, 12, 24 or 36.
The authors suggest that nevirapine may not be an appropriate candidate for therapeutic drug monitoring because the variability in concentrations of the drug is much less than for protease inhibitors, except in cases where drug-drug interactions are suspected.
Crommentuyn KM et al. Therapeutic drug monitoring of nevirapine reduces pharmacokinetic variability but does not affect toxicity or virologic success in the ATHENA study. J Aquir Immune Defic Syndr 39: 249-250, 2005.