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.
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.
Cozzi-Lepri
Alessandro
A
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
De Luca
Andrea
A
Phillips
Andrew N
AN
Bongiovanni
Marco
M
Di Giambenedetto
Simona
S
Mena
Maurizio
M
Moioli
Maria Cristina
MC
Arlotti
Massimo
M
Sighinolfi
Laura
L
Narciso
Pasquale
P
Lichtner
Miriam
M
Cauda
Roberto
R
Monforte
Antonella d'Arminio
Ad
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
D000480:Alkynes; D048588:Benzoxazines; D003521:Cyclopropanes; D015224:Dideoxynucleosides; D008055:Lipids; D010078:Oxazines; D018894:Reverse Transcriptase Inhibitors; D000099227:Abacavir; C098320:efavirenz