Effectiveness

Clinical studies have shown that abacavir (Ziagen) can reduce HIV viral load and improve immune function in the majority of people when taken in combination with at least two other anti-HIV drugs. It is regarded as a highly potent nucleoside reverse transcriptase inhibitor (NRTI) in people who have not taken previous antiretroviral therapy, although it often retains an anti-HIV effect in individuals who have previously taken treatment. Abacavir is active against HIV-1 and HIV-2.

Abacavir was licensed after the results of the CNA 3003 study showed that adding the drug to a combination of AZT (zidovudine, Retrovir) and 3TC (lamivudine, Epivir) led to more patients having suppressed viral loads in patients taking antiretroviral therapy for the first time.^[1] The CNAB 3005 study extended this by comparing abacavir to the protease inhibitor indinavir (Crixivan), in combination with AZT and 3TC, with both groups having similar viral load reductions.^[2]

Since its approval, studies have shown that abacavir is effective when used as a part of a dual NRTI ‘backbone.’ The CNA 30024 study showed that abacavir is just as effective in reducing viral load as AZT when combined with 3TC and efavirenz (Sustiva). However, people who received abacavir had a significantly better CD4 cell count increase after 48 weeks.^[3]

The ZODIAC study showed that once-daily dosing of abacavir was just as safe and effective as the twice-daily separate doses in patients starting antiretroviral therapy for the first time. The two dosing schedules produced similar rates of side-effects.^[4]

Like AZT and d4T (stavudine, Zerit), abacavir is able to cross the blood-brain barrier and combat HIV in the central nervous system. One study of treatment-experienced people with dementia found that abacavir reduces the viral load in the cerebrospinal fluid that surrounds the brain and spinal cord.^[5]