Lamivudine is a synthetic nucleoside analogue reverse transcriptase inhibitor (NRTI) with potent activity against human immunodeficiency virus type 1 (HIV-1), HIV-2, and hepatitis B virus (HBV). It is phosphorylated intracellularly to its active 5'-triphosphate metabolite, lamivudine triphosphate, which inhibits viral reverse transcriptase via DNA chain termination. In India, it is a cornerstone of first-line antiretroviral therapy (ART) for HIV and a key component of HBV treatment, widely available due to its inclusion in the National AIDS Control Programme (NACP) and generic manufacturing.
Adult: HIV (in combination): 300 mg once daily OR 150 mg twice daily. HBV: 100 mg once daily. Note: 100mg tablet is the standard strength for HBV monotherapy. For HIV, it is typically part of a 300mg dose (e.g., one 300mg tablet or two 150mg tablets).
Note: Can be taken with or without food. For consistent absorption, take at the same time each day. The tablet should be swallowed whole with water. For patients with difficulty swallowing, some brands offer dispersible tablets or oral solution.
Lamivudine is a cytosine analogue. After passive diffusion and active transport into cells, it is phosphorylated by cellular kinases to lamivudine triphosphate (L-TP). This active form competes with the natural substrate, deoxycytidine triphosphate (dCTP), for incorporation into the growing viral DNA chain by the reverse transcriptase (RT) enzyme of HIV and HBV polymerase. Incorporation of L-TP results in chain termination because it lacks the 3'-hydroxyl group necessary for forming the next phosphodiester bond.
Pregnancy: Pregnancy Category C (US FDA). However, extensive data from the Antiretroviral Pregnancy Registry show no increased risk of major birth defects. Lamivudine is recommended for use in pregnant women with HIV as part of combination ART to prevent mother-to-child transmission. It crosses the placenta.
Driving: Lamivudine has been associated with dizziness and fatigue. Patients should be cautioned about driving or operating machinery if they experience these effects.
| Trimethoprim/Sulfamethoxazole (Cotrimoxazole) | Increases lamivudine AUC by ~40% due to competition for renal tubular secretion. Clinical significance is minimal, but monitor for increased lamivudine side effects in renal impairment. | Moderate |
| Zidovudine (AZT) | Pharmacokinetic interaction is minimal. However, they are used in combination for synergistic antiviral effect. Increased risk of neutropenia/anemia with the combination. | Moderate |
| Ribavirin | Potential increased risk of lactic acidosis and hepatic decompensation when used with other NRTIs like lamivudine in HIV/HCV co-infection. Use with caution. | Major |
| Other drugs excreted by active renal secretion (e.g., cimetidine) | Potential for increased plasma concentrations of either drug. Monitor. | Moderate |
| Interferon-alfa | Used in combination for HBV. Additive risk of myelosuppression (neutropenia, thrombocytopenia). | Moderate |
Same composition (Lamivudine (100mg)), different brands: