Drug Guide
Emtricitabine; Tenofovir Disoproxil Fumarate
Classification
Therapeutic: antiretroviral for HIV infection and PrEP
Pharmacological: nucleoside/nucleotide reverse transcriptase inhibitor (NRTI)
FDA Approved Indications
- HIV-1 infection in combination with other antiretrovirals
- Pre-exposure prophylaxis (PrEP) for HIV prevention in high-risk individuals
Mechanism of Action
Emtricitabine and tenofovir disoproxil fumarate are nucleoside/nucleotide reverse transcriptase inhibitors that block the activity of reverse transcriptase, an enzyme crucial for HIV replication, thereby inhibiting viral DNA synthesis.
Dosage and Administration
Adult: 200 mg emtricitabine + 300 mg tenofovir disoproxil fumarate once daily, with or without food
Pediatric: Not approved for HIV treatment or PrEP in children less than 17 years; dosing as per clinical guidelines
Geriatric: Adjust based on renal function; consider comorbidities
Renal Impairment: Dose adjustment necessary for creatinine clearance less than 60 mL/min
Hepatic Impairment: No dose adjustment recommended for mild impairment; caution in severe impairment
Pharmacokinetics
Absorption: Both drugs are well absorbed orally
Distribution: Wide distribution, including into tissues and bodily fluids
Metabolism: Minimal metabolism for tenofovir; emtricitabine is phosphorylated intracellularly to active form
Excretion: Primarily renal excretion via filtration and secretion
Half Life: Emtricitabine: approximately 10 hours; Tenofovir disoproxil fumarate: approximately 17 hours
Contraindications
- Hypersensitivity to emtricitabine, tenofovir disoproxil fumarate, or any component of the formulation
Precautions
- Renal impairment, Hepatitis B virus infection (careful monitoring needed)
Adverse Reactions - Common
- Nausea (Frequent)
- Headache (Frequent)
- Insomnia (Common)
Adverse Reactions - Serious
- Lactic acidosis and severe hepatomegaly with steatosis (Rare)
- Renal toxicity including proximal renal tubulopathy (Rare)
- Bone mineral density loss (Less common)
Drug-Drug Interactions
- Nephrotoxic agents (e.g., aminoglycosides, NSAIDs)
- Emtricitabine or tenofovir with other antiretrovirals causing mitochondrial toxicity
Drug-Food Interactions
- None significant
Drug-Herb Interactions
- Limited data, caution advised with herbal products
Nursing Implications
Assessment: Monitor renal function (serum creatinine, eGFR), liver function, and adherence
Diagnoses:
- Risk of renal impairment
- Potential for medication nonadherence
Implementation: Educate patient on adherence, monitor labs regularly, counsel on side effects
Evaluation: Assess viral load, renal function, and patient adherence periodically
Patient/Family Teaching
- Take medication exactly as prescribed, with or without food
- Report signs of renal problems (e.g., swelling, fatigue), bone pain, or allergic reactions
- Educate on HIV prevention methods for at-risk contacts
Special Considerations
Black Box Warnings:
- Lactic acidosis/hypersensitivity (emtricitabine)
- Lactic acidosis and severe hepatomegaly with steatosis (tenofovir)
Genetic Factors: HIV subtype or patient genetics do not significantly impact drug choice
Lab Test Interference: Can cause asymptomatic increases in serum creatinine and decreases in serum phosphate
Overdose Management
Signs/Symptoms: Nausea, vomiting, dizziness, hypotension, dehydration, possible renal failure
Treatment: Supportive care, remove drug through hemodialysis if necessary, monitor renal function, no specific antidote
Storage and Handling
Storage: Store at room temperature 20-25°C (68-77°F), protect from moisture and light
Stability: Stable as per manufacturer’s expiration date under recommended storage conditions