Two recent, fixed associations of antiretroviral nucleos(t)ide analogues. A prospective assessment of their therapeutic use in HIV disease management: a field study

Background

The introduction of novel, fixed NRTI combinations (emtricitabine-tenofovir, E-T, and lamivudine-abacavir, L-A), expanded the available spectrum of antiretroviral formulations, and indirectly increased patient's adherence, since both these combinations are taken as a one pill-once daily regimen.

Methods

A prospective survey of the use of these two fixed NRTI combinations was performed in our cohort of over 1,700 HIV-infected patients (p).

Results

During 12 consecutive months, 334 p received for the first time E-T (262 cases), or L-A (72 p). Among the 88 p naïve to all antiretrovirals, E-T was given to 66 p (75.0%), mostly associated with efavirenz (51 p), or different PI combinations (15 p), whereas L-A was administered to 22 p only (in 18 of them in association with PI). In the remaining 246 p, E-T or L-A therapy replaced a prior regimen, predominantly associated with PI (141 cases p), versus efavirenz (48 p), or oher combinations (57 p). Among the 246 pre-treated p, E-T (194 p), still prevailed over L-A (50 p), and the therapeutic change was due to failure and resistance (89 p), and in the majority of cases to toxicity or poor tolerability (146 p). Both fixed NRTI combinations were well tolerated, with only three cases of L-A suspension due to abacavir hypersensitivity, and two cases of E-T interruption due to kidney abnormalities.

Discussion

From our preliminary experience, a major role seems played by E-T in first-line treatments (preferably among "compact" regimens based on efavirenz), while the apparently increased L-A prescription to pre-treated p is attributable to the different genetic barrier of abacavir (which is often introduced in association with PI). The present availability to two more fixed NRTI combinations advantaged by once-daily administration strongly encourages further "head to head" studies in both first-line and experienced p, in order to better exploit and target their therapeutic potential and their convenience features.