title: Nonnucleoside reverse transcriptase inhibitor concentrations during treatment interruptions and the emergence of resistance: a substudy of the ISS-PART Trial.
abstract: Emergence of resistance is one of the drawbacks associated with treatment interruptions (TI), especially when regimens include nonnucleoside reverse transcriptase inhibitors (NNRTIs), because of their long half-life. ISS-PART was a randomized trial comparing a continuous treatment arm with a TI arm in which 136 patients underwent five treatment interruptions, each followed by 3 months of therapy, over 2 years. To minimize the potential risk of developing resistance, patients on NNRTIs were requested, at each TI, to interrupt nevirapine (NVP) or efavirenz (EFV) 3 or 6 days before the other drugs, respectively. To determine if a difference in drug levels existed during TIs between patients with and without resistance we compared NNRTI concentrations in the 12 patients (6 on NVP and 6 on EFV) who developed NNRTI mutations during TIs with those of 20 patients (10 on NVP and 10 on EFV) who retained a wild-type virus. Genotypic resistance and drug concentrations were analyzed on plasma samples collected 15 days after each drug interruption. Overall, EFV was quantifiable in 28% (16/57) and NVP in 22.9% (14/61) of evaluable samples collected during TIs, with no difference between patients with and without mutations. Median EFV or NVP concentrations at each TI were not significantly different between patients with and without mutations. Although the staggered stop strategy was not completely effective in preventing exposure to suboptimal levels, no evident correlation was found between NNRTI concentrations and the emergence of resistance, suggesting that other factors (such as the presence of drug-resistant minority variants) could also play an important role in these patients.
authors.affiliation: Department of Therapeutic Research and Medicines Evaluation, Istituto Superiore di Sanità, Rome, Italy.
authors.forename: Maria
authors.initials: M
authors.lastname: Pirillo
authors.forename: Lucia
authors.initials: L
authors.lastname: Palmisano
authors.forename: Manuela
authors.initials: M
authors.lastname: Pellegrini
authors.forename: Clementina
authors.initials: C
authors.lastname: Galluzzo
authors.forename: Liliana
authors.initials: L
authors.lastname: Weimer
authors.forename: Raffaella
authors.initials: R
authors.lastname: Bucciardini
authors.forename: Vincenzo
authors.initials: V
authors.lastname: Fragola
authors.forename: Mauro
authors.initials: M
authors.lastname: Andreotti
authors.forename: Emilia
authors.initials: E
authors.lastname: Marchei
authors.forename: Simona
authors.initials: S
authors.lastname: Pichini
authors.forename: Stefano
authors.initials: S
authors.lastname: Vella
authors.forename: Marina
authors.initials: M
authors.lastname: Giuliano
mesh_terms: D000328:Adult; D000368:Aged; D000480:Alkynes; D019380:Anti-HIV Agents / Q000008:administration & dosage / Q000493:pharmacokinetics / Q000494:pharmacology; D048588:Benzoxazines / Q000008:administration & dosage / Q000493:pharmacokinetics / Q000494:pharmacology; D003521:Cyclopropanes; D004334:Drug Administration Schedule; D024882:Drug Resistance, Viral / Q000235:genetics; D004359:Drug Therapy, Combination; D005260:Female; D015658:HIV Infections / Q000188:drug therapy* / Q000821:virology; D015497:HIV-1 / Q000187:drug effects / Q000235:genetics; D006801:Humans; D008297:Male; D008875:Middle Aged; D019829:Nevirapine / Q000008:administration & dosage / Q000493:pharmacokinetics / Q000494:pharmacology; D012367:RNA, Viral / Q000097:blood; D018894:Reverse Transcriptase Inhibitors / Q000008:administration & dosage / Q000493:pharmacokinetics / Q000494:pharmacology; D016896:Treatment Outcome; D055815:Young Adult
chemical_list: D000480:Alkynes; D019380:Anti-HIV Agents; D048588:Benzoxazines; D003521:Cyclopropanes; D012367:RNA, Viral; D018894:Reverse Transcriptase Inhibitors; D019829:Nevirapine; C098320:efavirenz