Lamivudine

Lamivudine is a synthetic cytidine analogue that inhibits viral reverse transcriptase and hepatitis B virus polymerase. It is used in combination antiretroviral therapy for HIV and as an antiviral for chronic hepatitis B.

Nucleoside reverse-transcriptase inhibitor: An antiviral drug that mimics a nucleoside and disrupts viral DNA synthesis by reverse transcriptase. Lamivudine belongs to this drug class and blocks HIV DNA synthesis after cellular activation.
Antiretroviral therapy: Treatment of retroviral infections using drugs that inhibit viral replication. Lamivudine is used for HIV as part of a combination regimen, not alone.
Emtricitabine: A cytidine analogue antiretroviral used with other drugs to treat HIV and prevent infection. It resembles lamivudine in structure and activity, but is generally dosed once daily.
Antiviral drug resistance: Reduced susceptibility of a virus to a drug because inherited viral changes impair its action. Lamivudine resistance can develop rapidly when viral replication continues under drug pressure.
Reverse transcriptase: An enzyme that copies RNA into DNA, used by retroviruses and some other viruses. Lamivudine’s active metabolite inhibits this enzyme in HIV.
HIV: A retrovirus that attacks immune cells and can cause acquired immunodeficiency syndrome. Lamivudine suppresses HIV replication when combined with other antiretroviral drugs.
Tenofovir disoproxil fumarate: An oral prodrug of tenofovir used to treat HIV and chronic hepatitis B. It is active against both viruses and has a higher barrier to hepatitis B resistance than lamivudine.
YMDD motif: A conserved amino-acid sequence in the catalytic region of hepatitis B virus polymerase. Substitutions in this motif can confer resistance to lamivudine in hepatitis B.
Lamivudine triphosphate: The phosphorylated, active form of lamivudine inside cells. Cellular enzymes convert lamivudine into this form, which competes with natural nucleotides.
Chronic hepatitis B: Long-lasting infection with hepatitis B virus that can cause liver inflammation, cirrhosis, or cancer. Lamivudine can reduce viral replication in this infection, though resistance limits long-term use.

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