Nurses Compass
Drug Guide
Emtricitabine and Tenofovir Alafenamide
Classification
Therapeutic: Antiretroviral for HIV infection and prophylaxis
Pharmacological: Nucleoside Reverse Transcriptase Inhibitors (NRTIs) / Nucleoside/Nucleotide Reverse Transcriptase Inhibitors (NRTIs)
FDA Approved Indications
- Treatment of HIV-1 infection in adults and pediatric patients aged 12 years and older weighing at least 35 kg.
- Pre-exposure prophylaxis (PrEP) for HIV-1 infection in at-risk adults and adolescents weighing at least 35 kg.
Mechanism of Action
Emtricitabine and Tenofovir Alafenamide are nucleotide reverse transcriptase inhibitors that block the activity of HIV reverse transcriptase, an enzyme crucial for viral replication. Tenofovir inhibits HIV DNA synthesis by competing with natural substrate deoxyadenosine 5'-triphosphate (dATP). Emtricitabine is a synthetic nucleoside analogue of cytidine that is incorporated into viral DNA, causing termination of DNA chain elongation.
Dosage and Administration
Adult: One tablet (200 mg emtricitabine/25 mg tenofovir alafenamide) once daily with or without food.
Pediatric: Not approved for pediatric use; consult specific guidelines for adolescent patients.
Geriatric: No specific dose adjustment required but caution in patients with renal impairment.
Renal Impairment: Contraindicated in patients with eGFR less than 30 mL/min. Dose adjustment needed in renal impairment.
Hepatic Impairment: Use with caution in severe hepatic impairment; no specific adjustments provided.
Pharmacokinetics
Absorption: Well absorbed following oral administration.
Distribution: Widely distributed; volume of distribution approximately 1-2 L/kg.
Metabolism: Tenofovir is not significantly metabolized by hepatic enzymes; emtricitabine is minimally metabolized.
Excretion: Primarily excreted unchanged in the urine via glomerular filtration and tubular secretion.
Half Life: Emtricitabine: approximately 10 hours; Tenofovir: approximately 15-18 hours.
Contraindications
- Hypersensitivity to emtricitabine, tenofovir, or any component of the formulation.
Precautions
- Renal impairment, Hepatic impairment, Osteomalacia, Bone mineral density loss, Lactic acidosis risk, Fanconi syndrome
Adverse Reactions - Common
- Nausea (Common)
- Fatigue (Common)
- Headache (Common)
- Dizziness (Common)
- Diarrhea (Common)
Adverse Reactions - Serious
- Lactic acidosis (Rare)
- Severe hepatomegaly with steatosis (Rare)
- Renal impairment or failure (Uncommon)
- Fanconi syndrome (Rare)
Drug-Drug Interactions
- Amiodarone (risk of lactic acidosis),
- Rifampin (reduces tenofovir levels),
- Metformin (increased risk of lactic acidosis)
Drug-Food Interactions
N/ADrug-Herb Interactions
N/ANursing Implications
Assessment: Monitor renal function (serum creatinine, eGFR), bone mineral density, and levels of HIV RNA and CD4 counts during therapy.
Diagnoses:
- Risk for renal impairment
- Risk for bone demineralization
Implementation: Administer once daily, counsel on adherence, monitor for side effects.
Evaluation: Assess virologic response, renal function, and patient adherence regularly.
Patient/Family Teaching
- Take medication exactly as prescribed, once daily.
- Report any symptoms of lactic acidosis, hypersensitivity, or renal issues.
- Maintain regular follow-up appointments for testing.
- Use additional precautions for HIV prevention and management.
Special Considerations
Black Box Warnings:
- Lactic acidosis and severe hepatomegaly with steatosis
Genetic Factors: Consider HLA-B*5701 testing before initiation of emtricitabine due to hypersensitivity risk.
Lab Test Interference: May interfere with serum creatinine measurements; use alternative testing if necessary.
Overdose Management
Signs/Symptoms: Nausea, vomiting, dizziness, increased risk of lactic acidosis.
Treatment: Supportive care; hemodialysis may be considered for overdose of tenofovir.
Storage and Handling
Storage: Store at room temperature, 20-25°C (68-77°F).
Stability: Stable under recommended storage conditions for the duration of the shelf life.