title: A comparison between abacavir and efavirenz as the third drug used in combination with a background therapy regimen of 2 nucleoside reverse-transcriptase inhibitors in patients with initially suppressed viral loads.
abstract: BACKGROUND
  Our objective was to compare the rate of viral rebound and therapy failure in patients receiving abacavir or efavirenz as the third drug (in addition to 2 non-abacavir nucleosides) in combination antiretroviral therapy (cART) and to compare the rate of metabolic alteration associated with these regimens.
  
  
  METHODS
  We conducted a multicohort prospective observational study of human immunodeficiency virus-infected patients who had attained viral loads < or = 80 copies/mL while receiving cART, without having previously received antiretrovirals. The rates of virological rebound, therapy failure, and lipid-level alteration during follow-up were calculated as the number of events divided by person-years of follow-up (PYFU). A multivariable analysis was performed using a Poisson regression model.
  
  
  RESULTS
  We studied a total of 744 patients; the median age was 37 years, 27% of the patients were female, and 41% were heterosexual. There was a total of 854 PYFU spent receiving efavirenz and 285 spent receiving abacavir. The nucleoside reverse-transcriptase inhibitor pairs most frequently used were zidovudine/lamivudine (66% of PYFU), stavudine/lamivudine (17.6%), and stavudine/didanosine (5.4%). The adjusted relative rates of virological failure and therapy failure for abacavir, compared with those for efavirenz, were 2.17 (95% confidence interval [CI], 1.12-4.18; P = .02) and 1.41 (95% CI, 1.01-2.01; P = .05), respectively.
  
  
  CONCLUSIONS
  Patients with virological suppression while receiving regimens containing abacavir appear more likely to experience virological and therapy failure than those receiving efavirenz as their third drug. Although this is a selected group of adherent patients, bias cannot be ruled out, because this is a nonrandomized comparison.
authors.affiliation: Department of Primary Care and Population Sciences, Royal Free and University College Medical School, University College London, United Kingdom. a.cozzi-lepri@pcps.ucl.ac.uk
authors.forename: Alessandro
authors.initials: A
authors.lastname: Cozzi-Lepri
authors.forename: Andrea
authors.initials: A
authors.lastname: De Luca
authors.forename: Andrew N
authors.initials: AN
authors.lastname: Phillips
authors.forename: Marco
authors.initials: M
authors.lastname: Bongiovanni
authors.forename: Simona
authors.initials: S
authors.lastname: Di Giambenedetto
authors.forename: Maurizio
authors.initials: M
authors.lastname: Mena
authors.forename: Maria Cristina
authors.initials: MC
authors.lastname: Moioli
authors.forename: Massimo
authors.initials: M
authors.lastname: Arlotti
authors.forename: Laura
authors.initials: L
authors.lastname: Sighinolfi
authors.forename: Pasquale
authors.initials: P
authors.lastname: Narciso
authors.forename: Miriam
authors.initials: M
authors.lastname: Lichtner
authors.forename: Roberto
authors.initials: R
authors.lastname: Cauda
authors.forename: Antonella d'Arminio
authors.initials: Ad
authors.lastname: Monforte
mesh_terms: D000163:Acquired Immunodeficiency Syndrome / Q000188:drug therapy* / Q000821:virology; D000328:Adult; D000368:Aged; D000480:Alkynes; D048588:Benzoxazines; D015331:Cohort Studies; D003521:Cyclopropanes; D015224:Dideoxynucleosides / Q000627:therapeutic use*; D004359:Drug Therapy, Combination; D005260:Female; D049674:History, 21st Century; D006801:Humans; D008055:Lipids / Q000097:blood; D008297:Male; D008875:Middle Aged; D010078:Oxazines / Q000627:therapeutic use*; D011446:Prospective Studies; D018894:Reverse Transcriptase Inhibitors / Q000627:therapeutic use*; D013997:Time Factors; D019562:Viral Load; D000099227:Abacavir
chemical_list: D000480:Alkynes; D048588:Benzoxazines; D003521:Cyclopropanes; D015224:Dideoxynucleosides; D008055:Lipids; D010078:Oxazines; D018894:Reverse Transcriptase Inhibitors; D000099227:Abacavir; C098320:efavirenz