EMTRICITABINE
Clinical safety rating: caution
Comprehensive clinical and safety monograph for EMTRICITABINE (EMTRICITABINE).
Nucleoside reverse transcriptase inhibitor; phosphorylated to emtricitabine triphosphate which competes with endogenous deoxycytidine triphosphate and incorporates into viral DNA causing chain termination.
| Metabolism | Minimal metabolism; undergoes oxidation and glucuronidation. Not a substrate of CYP450 enzymes. |
| Excretion | Renal: approximately 86% of the dose is excreted unchanged in urine via glomerular filtration and active tubular secretion. Biliary/fecal: minimal (<14% as unchanged drug and metabolites in feces). |
| Half-life | Terminal elimination half-life is approximately 10 hours (range 8–12 hours) in adults with normal renal function; prolonged to >20 hours in severe renal impairment (CrCl <30 mL/min). |
| Protein binding | Minimal (<4%) binding to plasma proteins. |
| Volume of Distribution | Apparent volume of distribution is approximately 1.0 L/kg (range 0.8–1.2 L/kg), indicating extensive distribution into total body water. |
| Bioavailability | Oral: approximately 93% (range 78–110%) in fasting state; food delays absorption but does not significantly reduce AUC. |
| Onset of Action | Oral: peak plasma concentrations achieved in 1–2 hours; antiviral effect begins within hours of initial dosing. |
| Duration of Action | Oral: due to intracellular phosphorylation, active triphosphate has a prolonged intracellular half-life of ~39 hours, supporting once-daily dosing. Plasma drug levels decline over 10 hours. |
| Molecular Weight | 247.24 |
200 mg orally once daily, typically in combination with other antiretroviral agents.
| Dosage form | CAPSULE |
| Renal impairment | CrCl >= 30 mL/min: 200 mg daily; CrCl 15-29 mL/min: 200 mg every 72 hours; CrCl < 15 mL/min or hemodialysis: not recommended. |
| Liver impairment | No dose adjustment required for mild to moderate hepatic impairment (Child-Pugh A or B). Not studied in severe impairment (Child-Pugh C). |
| Pediatric use | For children weighing >17 kg: 6 mg/kg (max 200 mg) orally once daily; for children weighing >33 kg: 200 mg orally once daily. Use oral solution in those unable to swallow capsules. |
| Geriatric use | No specific dose adjustment recommended based on age alone; monitor renal function and adjust dose according to CrCl as per renal impairment guidelines. |
| 1st trimester | Data from a large number of exposed pregnancies indicate no malformative or feto/neonatal toxicity. Emtricitabine can be used during the first trimester if clinically needed. |
| 2nd trimester | Available data do not suggest an increased risk of adverse pregnancy outcomes. Use only if benefit outweighs risk. |
| 3rd trimester | No evidence of fetal harm; may be used during the third trimester. Monitor for potential neonatal lactic acidosis and hepatic steatosis with NRTIs. |
Clinical note
Comprehensive clinical and safety monograph for EMTRICITABINE (EMTRICITABINE).
| Placental transfer | Emtricitabine crosses the placenta (cord blood:maternal plasma ratio ~1.0). Transport is passive and non-saturable based on in vitro studies. |
| Breastfeeding | Emtricitabine is excreted into human milk at low concentrations (milk:plasma ratio ~0.5). While the risk to the nursing infant is considered low, caution is advised due to potential for HIV transmission via breastfeeding and unknown long-term effects. In HIV-positive mothers, formula feeding is recommended where possible. |
■ FDA Black Box Warning
Not approved for treatment of chronic hepatitis B virus (HBV) infection; severe acute exacerbations of HBV reported in co-infected patients upon discontinuation. Not for use as PrEP in individuals with unknown or positive HIV-1 status.
| Serious Effects |
Hypersensitivity to emtricitabine or any component of the formulation
| Precautions | Lactic acidosis/severe hepatomegaly with steatosis (including fatalities). Immune reconstitution syndrome. Decreased bone mineral density. Renal impairment: dose adjustment required if CrCl <50 mL/min. Fat redistribution. Risk of HIV-1 resistance if used for PrEP in undiagnosed HIV-1 infection. |
| Food/Dietary | No significant food interactions. Emtricitabine can be taken with or without food. Avoid excessive alcohol intake, as it may exacerbate liver toxicity. |
Loading safety data…
| Lactation Rating | L2 (Probably Compatible) |
| Teratogenic Risk | Pregnancy category B. No evidence of teratogenicity in animal studies. Limited human data; however, no increased risk of major birth defects has been observed in first trimester exposures. Risk of HIV transmission to fetus outweighs potential risks. Caution in third trimester due to possible mitochondrial toxicity. |
| Fetal Monitoring | Monitor maternal HIV viral load, CD4 count, and renal function (serum creatinine, BUN). Monitor fetal growth with serial ultrasounds. Assess for anemia (CBC) due to potential bone marrow suppression. Check hepatic function if co-infected with hepatitis B. |
| Fertility Effects | No known significant effects on male or female fertility in animal studies. Limited human data; not associated with hormonal changes or impaired gametogenesis. May be used in ART programs without adjustment. |
| Clinical Pearls | Emtricitabine is a nucleoside reverse transcriptase inhibitor (NRTI) used for HIV-1 infection. It is available as a single agent and in combination formulations (e.g., Truvada with tenofovir disoproxil fumarate, Descovy with tenofovir alafenamide). Monitor renal function and bone density, especially with tenofovir-containing coformulations. Emtricitabine has activity against hepatitis B virus (HBV); abrupt discontinuation can cause severe HBV exacerbations. Dose adjustment required for CrCl <50 mL/min: 200 mg every 48 hours if CrCl 30-49, 200 mg every 72 hours if CrCl 15-29, and 200 mg every 96 hours if on hemodialysis. |
| Patient Advice | Take emtricitabine exactly as prescribed, usually once daily with or without food. · Do not stop taking this medication without consulting your doctor, as hepatitis B infection may worsen. · You may experience headache, diarrhea, nausea, or rash; report severe or persistent symptoms. · Emtricitabine does not cure HIV or prevent transmission; use condoms and avoid sharing needles. · Your doctor will monitor kidney function and bone density regularly, especially if on tenofovir combinations. · If you are pregnant or planning pregnancy, discuss with your healthcare provider as emtricitabine is often used in pregnancy. |