title: Plasma concentrations of efavirenz are associated with body weight in HIV-positive individuals.
abstract: BACKGROUND
  Efavirenz is among the most widely used antiretroviral drugs. Increased efavirenz exposure has been associated with CNS side effects and also with the chance of emergence of resistance upon treatment interruptions. The objective of this study was to evaluate factors associated with efavirenz plasma concentrations in a cohort of HIV-infected individuals.
  
  
  METHODS
  From July 2009 to March 2010, HIV-infected patients with efavirenz as part of antiretroviral therapy (600 mg at night), undetectable viral load for at least 1 year and CD4 cell count >200 cells/mm(3) were consecutively enrolled at the HIV/AIDS ambulatory care unit in southern Brazil. Plasma samples were taken 18-23 h after efavirenz last dose and analysed by validated ultra-performance liquid chromatography.
  
  
  RESULTS
  Forty-one subjects were included (21 females). Mean age and weight were 45.4 years and 70.9 kg, respectively. Mean efavirenz plasma concentration was 2.20 ± 2.17 mg/L. Most plasma concentrations (73%) were within the therapeutic window (1-4 mg/L); 17% were below and 10% above the limits. There were no significant associations between efavirenz concentration and age, CD4 cell count, time on antiretroviral treatment and gender. There was significant and inverse correlation between efavirenz concentrations and body weight (P = 0.013) and body mass index (P = 0.001).
  
  
  CONCLUSIONS
  In this cohort of well-controlled HIV-positive individuals, patients with lower weight or body mass index had a higher chance of presenting elevated plasma concentrations of efavirenz. Therapeutic drug monitoring to adjust dose might be a helpful tool to decrease efavirenz dose in order to minimize costs and adverse effects.
authors: School of Medicine, Universidade Federal do Rio Grande do Sul, Porto Alegre, RS, Brazil.
authors: Julia
authors: J
authors: Poeta
authors: Rafael
authors: R
authors: Linden
authors: Marina Venzon
authors: MV
authors: Antunes
authors: Lucia
authors: L
authors: Real
authors: Andréia Magalhães
authors: AM
authors: Menezes
authors: Jorge P
authors: JP
authors: Ribeiro
authors: Eduardo
authors: E
authors: Sprinz
mesh_terms: D000328:Adult; D000368:Aged; D000375:Aging; D000480:Alkynes; D019380:Anti-HIV Agents / Q000008:administration & dosage / Q000009:adverse effects / Q000097:blood*; D048588:Benzoxazines / Q000008:administration & dosage / Q000009:adverse effects / Q000097:blood*; D001835:Body Weight; D018791:CD4 Lymphocyte Count; D003521:Cyclopropanes; D016903:Drug Monitoring; D005260:Female; D015658:HIV Infections / Q000097:blood / Q000188:drug therapy* / Q000821:virology; D015497:HIV-1 / Q000187:drug effects; D006801:Humans; D008297:Male; D008875:Middle Aged; D018894:Reverse Transcriptase Inhibitors / Q000008:administration & dosage / Q000009:adverse effects / Q000097:blood*; D019562:Viral Load
chemical_list: D000480:Alkynes; D019380:Anti-HIV Agents; D048588:Benzoxazines; D003521:Cyclopropanes; D018894:Reverse Transcriptase Inhibitors; C098320:efavirenz