Lamivudine is a potent reverse transcriptase inhibitor of the class nucleoside analog reverse transcriptase inhibitor (NARTI). Lamivudine has been used for treatment of chronic hepatitis B at a lower dose than for treatment of HIV. Lamivudine was approved by the Food and Drug Administration in 1995 for use with Zidovudine (AZT). When HIV infects a cell, reverse transcriptase copies the viral single stranded RNA genome into a double-stranded viral DNA. The viral DNA is then integrated into the host chromosomal DNA which then allows host cellular processes, such as transcription and translation to reproduce the virus. RTIs block reverse transcriptase's enzymatic function and prevent completion of synthesis of the double-stranded viral DNA thus preventing HIV from multiplying.

Lamivudine is an analogue of cytidine. It can inhibit both types (1 and 2) of HIV reverse transcriptase and also the reverse transcriptase of hepatitis B. It needs to be phosphorylated to its triphosphate form before it is active. 3TC-triphosphate also inhibits cellular DNA polymerase.

In HIV, high level resistance is associated with the M184V/I mutation in the reverse transcriptase gene of the HIV virus. Lamivudine though continues to have a partial anti-viral effect even in the presence of the M184V mutation.

Formal Chemical Name (IUPAC)
4-amino-1-((2R,5S)-2-(hydroxymethyl)-1,3-oxathiolan-5-yl)pyrimidin-2(1H)-one

References

http://en.wikipedia.org/wiki/Lamivudine