Lamivudine. A review of its antiviral activity, pharmacokinetic properties and therapeutic efficacy in the management of HIV infection.

Lamivudine is a dideoxynucleoside analogue which undergoes intracellular phosphorylation to the putative active metabolite, lamivudine triphosphate. Lamivudine triphosphate prevents HIV replication by competitively inhibiting viral reverse transcriptase. Lamivudine has a unique resistance profile and has the ability to delay resistance to zidovudine and restore zidovudine sensitivity in zidovudine-experienced patients. Combination antiretroviral drug therapy is now generally considered preferable to monotherapy as first-line treatment for patients with HIV infection. In double-blind trials in antiretroviral drug-experienced or -naive adults, improvements in surrogate markers of disease progression were significantly greater in patients receiving lamivudine plus zidovudine combination therapy than in patients who received either drug as monotherapy. Preliminary results of CAESAR, a large multicentre trial in patients with moderately advanced HIV infection receiving zidovudine-based treatment regimens, show a 54% reduction in the rate of disease progression or death with the addition of lamivudine, compared with the addition of placebo. Initial virological data from studies of combination regimens including lamivudine and protease inhibitors are also promising, although the longer term efficacy of these regimens remains to be established. Improvements in surrogate disease markers were also seen in children and adolescents with symptomatic HIV infection who received lamivudine monotherapy. Studies of lamivudine-containing combination therapy in children and adolescents are in progress, but few data have yet been published. Lamivudine is generally well tolerated as monotherapy or in combination with other antiretroviral agents in HIV-infected adults with CD4+ counts > or = 100 cells/microliter. Gastrointestinal disturbances were reported as the most common adverse events during lamivudine monotherapy or combination therapy. Lamivudine appears to be less well tolerated in patients with advanced disease (CD4+ cell counts < 100 cells/microliter), but more data are required to clarify its tolerability in such patients. Pancreatitis has been reported in children with advanced disease during treatment with the drug, but was not directly attributable to lamivudine therapy. Thus, lamivudine, administered in combination with zidovudine, is now established as an effective agent for the treatment of antiretroviral drug-experienced or -naive individuals with asymptomatic or symptomatic HIV disease. Moreover, encouraging preliminary data suggest that lamivudine is poised to become an important component of other regimens, in combination with drugs such as the protease inhibitors.