lamivudine
HIV nucleoside reverse transcriptase inhibitor· Brands: Epivir, Zeffix, HeptovirPO
Mechanism of action
Lamivudine is a nucleoside analogue that inhibits HIV reverse transcriptase. It is phosphorylated intracellularly to lamivudine triphosphate, which competes with deoxycytidine triphosphate for incorporation into viral DNA. Once incorporated, it lacks the 3'-hydroxyl group needed for chain elongation, causing premature termination of the proviral DNA chain.
Pharmacokinetics
Lamivudine is well absorbed orally, with a bioavailability of about 80%. It is widely distributed, including into the cerebrospinal fluid. It is mainly excreted unchanged in the urine via renal tubular secretion. The elimination half-life is approximately 5 to 7 hours, and it is not significantly metabolised.
Indications & dosing
HIV-1 infection in combination with other antiretroviral agents
150 mg twice daily or 300 mg once daily. Dose adjustment required in renal impairment.
- adult · PO: 150–300 mg OD or BID · 150 mg twice daily or 300 mg once daily. Dose adjustment required in renal impairment.
Chronic hepatitis B virus infection
Less commonly used due to high resistance rates; often used in combination with other agents or when other drugs unavailable.
- adult · PO: 100 mg OD · Less commonly used due to high resistance rates; often used in combination with other agents or when other drugs unavailable.
Contraindications & precautions
- Hypersensitivity to lamivudine or any component of the formulation · Anaphylaxis, skin rash, or other allergic reactions have been reported.
- Severe renal impairment (creatinine clearance < 30 mL/min) · Dose reduction is required; lamivudine may be used with dose adjustment, but caution is advised in severe impairment.
- Dose adjustment required in renal impairment; monitor creatinine clearance and adjust dose accordingly.
- Monitor for signs and symptoms of pancreatitis (abdominal pain, nausea, vomiting); discontinue if pancreatitis is suspected or confirmed.
- Monitor for lactic acidosis symptoms (e.g., deep rapid breathing, fatigue, nausea); discontinue if lactic acidosis or hepatic steatosis is suspected.
- In patients with hepatitis B co-infection, discontinuation of lamivudine may cause severe exacerbation of hepatitis; monitor liver function for at least 4 months after stopping.
- Do not use lamivudine as monotherapy for HIV infection due to rapid development of resistance; always use in combination with other antiretrovirals.
- Use with caution in patients with a history of pancreatitis or risk factors for pancreatitis.
Adverse effects
- Headache
- Nausea
- Diarrhoea
- Fatigue
- Pancreatitisserious
- Lactic acidosis with hepatic steatosisserious
- Peripheral neuropathy
Renal & hepatic adjustment
- eGFR 50+: No dose adjustment required.
- eGFR 30–49: Reduce dose to 150 mg once daily.
- eGFR 15–29: Reduce dose to 100 mg once daily.
- eGFR 0–14: Reduce dose to 50 mg once daily.
Monitoring, pregnancy & toxicity
- HIV viral load · At baseline, then every 3-6 months
- CD4 count · At baseline, then every 3-6 months
- Renal function (serum creatinine, eGFR) · At baseline, then periodically; more frequently if renal impairment
- Liver function tests (ALT, AST) · At baseline, then periodically; especially in co-infection or hepatitis B treatment
- Serum lipase/amylase and clinical signs of pancreatitis · Monitor for symptoms; test if suspected
- Blood count · At baseline; monitor if at risk of cytopenia
- Pregnancy: Lamivudine is commonly used in pregnancy as part of combination antiretroviral therapy. Available data indicate no increased risk of adverse outcomes, and it is a preferred agent in some guidelines. Always follow local guidelines and specialist advice.
- Toxicity: Pancreatitis (especially in paediatric patients) · Stop lamivudine, provide supportive care.
- Toxicity: Lactic acidosis and hepatic steatosis, rare but potentially fatal · Stop treatment, monitor lactate and liver function; supportive care.
- Toxicity: Peripheral neuropathy · Usually reversible on discontinuation; treat symptomatically.
- Toxicity: Overdose may cause nausea, vomiting, and rarely haematological toxicity · Supportive care; monitor blood counts. Haemodialysis may remove lamivudine.
Clinical notes
Lamivudine is used in combination with other antiretrovirals for HIV infection. It is also active against hepatitis B virus, but resistance can develop. The usual adult dose is 300 mg daily, either as 150 mg twice daily or 300 mg once daily. Dose adjustment is needed in renal impairment. Monitor for lactic acidosis and pancreatitis, especially in children.
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BNF; local formulary