3TC (lamivudine) is a Nucleoside Reverse Transcriptase Inhibitor (NRTI) anti-viral drug indicated for the treatment of HIV in combination with other antiretroviral medications, and for the treatment of chronic Hepatitis B virus (HBV) infection.
Dosing & Administration
The dosage of 3TC for treating HIV infection differs from the dosage for treating chronic HBV infection. The drug can be used for HIV treatment for adults and children weighing 14 Kg or more, and off-label in children under three months, including neonates, for HBV. 3TC is also used off-label for HIV post-exposure prophylaxis for occupational and non-occupational exposures, and for HIV vertical transmission prophylaxis in neonates. The medication is available in various preparations and brand names. The product monograph should be consulted for dosage and administration instructions.
3TC requires dose adjustment in patients with a creatinine clearance <= 50 mL/min. No dose adjustments are indicated in liver dysfunction, but 3TC should be used with caution in these patients.
3TC is contraindicated in patients with hypersensitivity to the drug. Details are provided in the product monograph.
3TC is associated with generalized weakness, fatigue, myalgias, nausea/vomiting, abdominal pain, light-headedness, and palpations. A complete list of potential adverse effects is provided in the product monograph.
3TC has been associated with severe and even fatal cases of hepatomegaly with steatosis or lactic acidosis, particularly in women and the obese. Screening and monitoring recommendations are listed the product monograph.
Patients with HBV infection who discontinue 3TC may experience severe acute exacerbations of hepatitis. As such, laboratory and clinical liver parameters should be closely monitored following discontinuation. Details are given in the product monograph.
Due to its high rate of drug resistance in HBV, 3TC should only be used if another antiviral HBV drug with less potential for resistance cannot be used.
All patients who test positive for HIV infection should be screened for comorbid HBV and Hepatitis C virus (HCV) infection. Co-infected patients should be started on an antiretroviral regimen targeting co-infected viruses, regardless of CD4 counts or viral loads. Current HIV treatment guidelines outline drug regimens and prescribing considerations.
3TC is associated with a large number of drug-drug and herbal interactions and contraindications. These are listed in the product monograph. Of particular note, 3TC should not be used in combination with cladribine or emtricitabine.
Pregnancy & Lactation
Data from the Antiretroviral Pregnancy Registry (n>11,000) does not show lamivudine to be associated with an increase in the incidence of major birth defects above baseline. If treatment is discontinued for pregnancy, patients should be monitored for exacerbation of HBV infection. Lamivudine is excreted in the breast milk. The CDC recommends that all HIV positive women, treated or untreated, avoid breastfeeding to prevent vertical transmission of the virus.
3TC overdose should be treated with standard supportive care. Lamivudine may be dialyzable.
Alternative Brand Names
3TC is available under the brand names Heptovir, Epivir, and Epivir-HBV and as a component of the combination medications Cimduo, Combivir, Epzicom, Triumeq, and Trizivir.
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