Makindo Medical Notes

💊 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

• Emtricitabine – British National Formulary
• BHIVA Guidelines for the Treatment of HIV (2023)
• NICE NG93: HIV Testing and Management
• Harrison’s Principles of Internal Medicine, 21st Edition – HIV Pharmacology