Abacavir: new preparation. Risks limit the value.

(1) Abacavir, a nucleoside inhibitor of HIV reverse transcriptase, is indicated for the treatment of HIV-infected adults, in combination with other antiretroviral drugs. (2) The assessment file is limited mainly to trials involving patients who have never received other antiretroviral drugs. There are no comparisons of abacavir plus two other nucleoside inhibitors versus three nucleoside inhibitors or versus one non nucleoside inhibitor plus two nucleoside inhibitors. (3) According to initial results the optimal dose regimen of abacavir in adults appears to be 300 mg twice a day. The lamivudine + zidovudine + abacavir combination reduces viral load more strongly than the lamivudine + zidovudine combination in patients not previously treated with antiretroviral drugs. Preliminary results suggest that the same applies to patients previously treated with antiretroviral drugs. (4) A trial involving 562 previously untreated patients showed that the effect of the abacavir + lamivudine + zidovudine combination (total of 4 tablets a day) was not significantly different from that of the indinavir + lamivudine + zidovudine combination (8 tablets a day) after 48 weeks of treatment. (5) In clinical trials, approximately 3% of adults and 5% of children had hypersensitivity reactions to abacavir. Under the strict conditions of the trials it was not always possible to avoid abacavir rechallenge, which carries a risk of a new, potentially fatal hypersensitivity reaction. (6) The risk-benefit ratio of abacavir is currently unfavourable in children, who must not be prescribed the drug. (7) The risk of drug interactions with abacavir is low.