EMTRIVA
Clinical safety rating: caution
Comprehensive clinical and safety monograph for EMTRIVA (EMTRIVA).
Nucleoside reverse transcriptase inhibitor; emtricitabine is phosphorylated to emtricitabine 5'-triphosphate which competes with deoxycytidine 5'-triphosphate for incorporation into viral DNA, resulting in chain termination.
| Metabolism | Emtricitabine undergoes limited metabolism; approximately 86% of the dose is excreted unchanged in the urine via glomerular filtration and tubular secretion. |
| Excretion | Renal excretion of unchanged drug (~86%) by glomerular filtration and active tubular secretion; fecal excretion (<1%) |
| Half-life | Terminal elimination half-life ~10 hours (mean 10 h, range 7-14 h) in adults; prolonged in renal impairment (up to 90 h in severe impairment) |
| Protein binding | <4% bound to plasma proteins (primarily albumin); minimal binding |
| Volume of Distribution | ~1.3 L/kg (approximate 100 L total); extensive distribution into tissues including CSF (ratio ~0.5-0.8) |
| Bioavailability | Oral: 93% (range 84-100%) |
| Onset of Action | Oral: Maximal antiretroviral effect within 1-2 weeks; time to steady state ~3-5 days |
| Duration of Action | 24 hours with once-daily dosing due to intracellular active metabolite (emtricitabine triphosphate) half-life >39 hours |
| Molecular Weight | 247.24 |
Emtricitabine 200 mg orally once daily.
| Dosage form | CAPSULE |
| Renal impairment | CrCl 30-49 mL/min: 200 mg every 48 hours; CrCl 15-29 mL/min: 200 mg every 72 hours; CrCl <15 mL/min or hemodialysis: 200 mg every 96 hours (on day of hemodialysis, administer after dialysis). |
| Liver impairment | No dose adjustment required for mild to moderate hepatic impairment. Not studied in severe hepatic impairment. |
| Pediatric use | For children weighing ≥33 kg: 200 mg once daily. For <33 kg: consult specific pediatric formulations and weight-based dosing (e.g., oral solution 10 mg/mL: 6 mg/kg once daily, max 240 mg). |
| Geriatric use | Dose selection based on renal function; monitor CrCl closely as age-related decline is common. No specific geriatric dose adjustments beyond renal considerations. |
| 1st trimester | Emtricitabine is generally considered safe in the first trimester. Animal studies showed no evidence of teratogenicity at clinically relevant doses. Human data from the Antiretroviral Pregnancy Registry do not indicate an increased risk of birth defects. |
| 2nd trimester | No specific fetal risks identified; continued use is recommended for HIV treatment. Monitor for maternal liver function and hematologic parameters. |
| 3rd trimester | No known adverse fetal effects; continued use is recommended to prevent vertical transmission. No evidence of third-trimester toxicity. |
Clinical note
Comprehensive clinical and safety monograph for EMTRIVA (EMTRIVA).
| Placental transfer | Emtricitabine crosses the placenta readily, achieving fetal concentrations similar to maternal plasma levels. It is a nucleoside analog with passive diffusion; placental transfer is confirmed in ex vivo and in vivo studies. |
| Breastfeeding |
■ FDA Black Box Warning
Posttreatment acute exacerbation of hepatitis B has been reported in patients coinfected with HBV who discontinue EMTRIVA. Hepatic function should be monitored closely in these patients.
| Serious Effects |
Hypersensitivity to emtricitabine or any component of the formulationConcurrent use with other nucleoside analogs with similar toxicity profiles (e.g., lamivudine, tenofovir disoproxil fumarate) without dose adjustment in renal impairment
| Precautions | Lactic acidosis/severe hepatomegaly with steatosis; immune reconstitution syndrome; increased risk of hepatitis B exacerbation upon discontinuation; decreased bone mineral density; renal impairment |
| Food/Dietary | No food restrictions. Emtricitabine can be taken with or without food. No clinically significant food-drug interactions. |
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| Emtricitabine is excreted into human breast milk at low concentrations (approximately 2-3% of maternal dose). In the setting of HIV infection, breastfeeding is contraindicated in high-resource settings due to risk of transmission. In resource-limited settings where replacement feeding is not feasible, WHO recommends maternal ART including emtricitabine during breastfeeding to reduce transmission risk. |
| Lactation Rating | L3 (Moderately Safe) or 'Probably Compatible' depending on context; however, for HIV-positive mothers, breastfeeding is generally not recommended in developed countries. |
| Teratogenic Risk | Emtricitabine is classified as FDA Pregnancy Category B. Human studies have not demonstrated an increased risk of major birth defects or miscarriage. However, due to insufficient data in the first trimester, it should be used only if clearly needed. In the second and third trimesters, no specific fetal risks have been identified. |
| Fetal Monitoring | Monitor maternal liver function tests, renal function, and complete blood counts. Perform HIV RNA viral load and CD4+ count regularly. Fetal monitoring includes ultrasound for growth and anatomy. |
| Fertility Effects | No known adverse effects on fertility in humans. Animal studies did not show impaired fertility. |
| Clinical Pearls | Emtricitabine is a nucleoside reverse transcriptase inhibitor (NRTI) used for HIV-1 infection. It is often co-formulated with tenofovir disoproxil fumarate or tenofovir alafenamide and emtricitabine. Do not use as monotherapy due to rapid resistance development. Monitor renal function before and during therapy; dose adjustment required for CrCl <50 mL/min. Can cause lactic acidosis and severe hepatomegaly with steatosis, especially in obese patients or those with liver disease. Screen for hepatitis B co-infection before starting; emtricitabine has activity against HBV, but discontinuation can cause severe flare-ups. Administer with or without food. Once-daily dosing (200 mg capsule or 240 mg/24 mL oral solution). |
| Patient Advice | Take exactly as prescribed every day at the same time to maintain effective levels. · Do not skip doses as this can lead to resistance and treatment failure. · Common side effects include headache, diarrhea, nausea, and skin discoloration (palms/soles) which is harmless. · Report symptoms of lactic acidosis (unexplained tiredness, muscle pain, abdominal pain with nausea/vomiting) or liver problems (dark urine, jaundice, right upper quadrant pain). · Emtricitabine does not cure HIV; use condoms to prevent transmission. · If you have hepatitis B, do not stop emtricitabine without consulting your doctor as it may worsen hepatitis. · Inform your doctor of all medications, including over-the-counter and herbal products (e.g., St. John's wort may reduce effectiveness). · Store at room temperature, away from moisture and heat. |