💊 Key point: Emtricitabine (FTC) is a well-tolerated Nucleoside Reverse Transcriptase Inhibitor (NRTI) used in most modern HIV and hepatitis B regimens. ⚠️ Rare but serious toxicities include lactic acidosis, hepatomegaly with steatosis, and post-treatment hepatitis B flare in co-infected patients.
🧠 About
- Emtricitabine (FTC) is a synthetic analogue of cytidine that inhibits viral replication in HIV-1 and hepatitis B virus (HBV).
- It is among the best-tolerated antiretrovirals, typically co-formulated with tenofovir (as Truvada®) or as part of fixed-dose combinations like Atripla® or Biktarvy®.
- Always check the BNF entry for the latest guidance on dosing and combination regimens.
⚙️ Mode of Action
- Emtricitabine is a Nucleoside Reverse Transcriptase Inhibitor (NRTI).
- It is phosphorylated intracellularly to its active triphosphate form, which competes with natural deoxycytidine triphosphate during viral DNA synthesis.
- Incorporation into viral DNA causes chain termination, halting replication of HIV-1 and HBV.
- Its long intracellular half-life allows once-daily dosing.
💊 Indications & Dosing
- HIV infection: 200 mg once daily (capsule) or 240 mg once daily (oral solution).
- Hepatitis B: Used off-label or in fixed-dose combination where co-infection exists.
- Pre-Exposure Prophylaxis (PrEP): Part of the tenofovir/emtricitabine combination (Truvada®) given once daily.
- No food restriction - may be taken with or without food.
⚠️ Interactions
- Few major interactions - minimal involvement with cytochrome P450 system.
- Do not combine with lamivudine (3TC) due to overlapping mechanism and potential cross-resistance.
- See BNF for specific interaction details.
⚕️ Cautions
- Renal impairment: Reduce dose or extend dosing interval (renally excreted unchanged).
- HBV co-infection: Stopping therapy can cause severe hepatitis flares - monitor liver function closely after discontinuation.
- Lactic acidosis and hepatic steatosis may occur rarely due to mitochondrial toxicity (a class effect of NRTIs).
🚫 Contraindications
- Hypersensitivity to emtricitabine or formulation excipients.
- Use with caution in advanced hepatic disease or previous lactic acidosis.
💥 Side Effects
- Common: Headache, diarrhoea, nausea, fatigue, rash.
- Distinctive: Hyperpigmentation of palms or soles (benign and reversible).
- Rare: Lactic acidosis, hepatomegaly with steatosis, hepatic flare in HBV co-infection.
📖 Educational Summary
Emtricitabine and lamivudine are near-identical drugs in structure and mechanism, both mimicking cytidine and targeting the same enzyme.
FTC is preferred for its longer half-life and once-daily dosing, which supports fixed-dose combination therapy - a major advance in adherence and viral suppression.
Its tolerability, safety, and dual HIV/HBV activity make it a cornerstone of modern regimens, including PrEP and first-line ART.
Teaching point: Emtricitabine’s rare palm hyperpigmentation is a benign cosmetic change and a useful clinical clue to its presence in a regimen.
📚 References
