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. |
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 | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Comprehensive clinical and safety monograph for EMTRICITABINE (EMTRICITABINE).
| Breastfeeding | Not recommended for breastfeeding mothers with HIV in resource-rich settings due to risk of HIV transmission. M/P ratio is approximately 0.033, indicating minimal excretion into breast milk. However, in HIV-negative mothers, it is contraindicated. Weigh risks versus benefits; alternative antiretrovirals preferred. |
| 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. |
■ 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. Co-administration with lamivudine or other cytidine analogues.
| 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. |
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| 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. |