3TC (lamivudine, Epivir) is generally a safe drug, with fewer side-effects than other nucleoside reverse transcriptase inhibitors (NRTIs). Its commonest side-effects are nausea, vomiting, diarrhoea, headache, tiredness, abdominal pain, peripheral neuropathy (tingling and pain in the feet and hands) and insomnia. Nausea and diarrhoea can be controlled with other medicines, which can be prescribed before starting 3TC. 3TC’s side-effects are most likely to occur during the early weeks of treatment.

Discontinuation of 3TC may result in a flare-up of hepatitis B infection in people with HIV / HBV co-infection. Careful monitoring of these patients is advised.

Less common side-effects of 3TC are neutropenia (low white blood cell counts) and rash. These may be more severe among people with low CD4 cell counts. There have also been reports of hair loss, severe anaemia and lactic acidosis (a serious increase in levels of lactic acid in the blood) among people receiving 3TC, while pancreatitis has been reported in children.