Long-term results of initial therapy with abacavir and Lamivudine combined with Efavirenz, Amprenavir/Ritonavir, or Stavudine

Efavirenz: a review

Efavirenz is a non-nucleoside reverse transcriptase inhibitor that in most treatment guidelines is recommended to be taken combined with two nucleoside analogue reverse transcriptase inhibitors, as a preferred first-line regimen for the treatment of HIV-1 infection. The antiretroviral efficacy of efavirenz-based combination regimens is good, as has been demonstrated in many clinical trials. Efavirenz has a long plasma half-life, which allows for once-daily dosing, but, as a consequence of this and the low genetic barrier, it is also prone to select for viral resistance when adherence to therapy is suboptimal. The most frequently encountered side effects are neuropsychiatric symptoms. These side effects are usually transient, but have been shown to persist for up to 2 years after initiation of therapy in some patients. This review outlines important and recent pharmacological and clinical data, which explain why efavirenz became a component of preferred treatment regimens today.

Long-term safety and tolerability of the lamivudine/abacavir combination as components of highly active antiretroviral therapy

BACKGROUND

Numerous large, long-term clinical trials have assessed the safety and efficacy of the two antiretroviral nucleoside analogs lamivudine and abacavir as components of highly active antiretroviral therapy for the treatment of patients with HIV-1 infection. This analysis pools the safety data on multi-drug regimens containing lamivudine/abacavir in combination with a protease inhibitor, non-nucleoside reverse transcriptase inhibitor, or nucleoside reverse transcriptase inhibitor.

METHODS

Data are presented from 2279 treatment-naive HIV-1-infected patients who were enrolled in one of five clinical trials that assessed the safety and tolerability of lamivudine/abacavir in combination with a third antiretroviral agent. The well characterised combination of lamivudine/zidovudine plus efavirenz was used as the comparator arm. All available safety data (including data beyond 48 weeks) were used in all analyses, which included calculation of treatment emergent laboratory values, adverse events (AEs), serious AEs, fatalities, drug discontinuations and any summaries by study week of safety data.

RESULTS

In the total lamivudine/abacavir group, 1585 of 2229 (71%) patients experienced at least one drug-related AE during the study compared with 247 of 325 (76%) patients in the lamivudine/zidovudine/efavirenz treatment group. The most common drug-related AEs reported during the study were diarrhoea (19%), nausea (18%) and dizziness (12%) in patients treated with lamivudine/abacavir plus a third agent, and nausea (31%), dizziness (27%) and headache (16%) in the comparator group. Overall, in the total lamivudine/abacavir group there were only three severe (Division of AIDS 1992 toxicity table grade 3 or 4) AEs that were reported in >1% of subjects: drug hypersensitivity, elevated ALT levels and elevated AST levels. In the lamivudine/zidovudine/efavirenz group, six severe AEs that occurred in >1% of the safety population were reported. The abacavir hypersensitivity reaction rate reported in these five studies was comparable with the previously reported rate. In addition, there were no patient fatalities attributed by investigators to the study drugs.

CONCLUSION

This analysis indicates that the combination of lamivudine/abacavir is generally safe for the majority of patients when used as part of combination therapy.

Non-nucleoside reverse transcriptase inhibitors: a review

Non-nucleoside reverse transcriptase inhibitors form the backbone of antiretroviral treatment for many HIV-infected individuals. The tolerability, pill burden and efficacy associated with this class of agents make them a frequent choice for first-line therapy. Here we review nevirapine and efavirenz in terms of efficacy, resistance and toxicity, focusing particularly on the use of nevirapine to prevent mother-to-child transmission in developing countries.

Abacavir/lamividune combination in the treatment of HIV-1 infection: a review

Consensus guidelines for the management of HIV infection recommend the use of two nucleoside analogues in combination with either a non-nucleoside reverse transcriptase inhibitor or a ritonavir-boosted protease inhibitor in therapy-naive patients. As adherence is crucial for treatment success, regimens with fewer pills, simpler dosing schedules and fewer adverse events have become the first choice for antiretroviral therapy. Fixed-dose combinations further improve the convenience of therapy. There are three dual-nucleoside fixed-dose combinations licensed for treating HIV-infected individuals, which include a combination of abacavir and lamivudine. This article reviews the pharmacology, efficacy, resistance profiles, safety and tolerability of abacavir focussing on its use in combination with lamivudine and discusses the role of this nucleoside backbone in antiretroviral therapy.