Nurses Compass
Drug Guide
Tenofovir Alafenamide Fumarate
Classification
Therapeutic: Antiviral, Reverse Transcriptase Inhibitor
Pharmacological: Nucleoside Reverse Transcriptase Inhibitor (NRTI)
FDA Approved Indications
- Chronic hepatitis B virus (HBV) infection in adults and pediatric patients 12 years and older with evidence of active replication
Mechanism of Action
Tenofovir Alafenamide is a prodrug of tenofovir. It inhibits HBV DNA polymerase by competing with natural deoxyadenosine 5'-triphosphate, leading to DNA chain termination and suppression of viral replication.
Dosage and Administration
Adult: For chronic hepatitis B, 25 mg once daily with or without food.
Pediatric: Not approved for pediatric use below 12 years or less than 35 kg.
Geriatric: No specific dosage adjustments; use with caution in elderly due to potential renal impairment.
Renal Impairment: Adjust dose in patients with creatinine clearance <30 mL/min or with renal impairment; see prescribing information for specifics.
Hepatic Impairment: Use with caution; no specific dose adjustment recommended.
Pharmacokinetics
Absorption: Well absorbed after oral administration, with food increasing absorption.
Distribution: Extensively distributed in tissues, high concentration in lymphatic tissue.
Metabolism: Not extensively metabolized; activated intracellularly to tenofovir diphosphate.
Excretion: Primarily excreted via renal pathways; dose adjustment needed in renal impairment.
Half Life: Approximately 45 hours for plasma; intracellular half-life of active metabolite is approximately 50 hours.
Contraindications
- Hypersensitivity to tenofovir alafenamide or any component of the formulation.
Precautions
- Renal impairment, bone mineral density loss, lactic acidosis, hepatitis B flare upon discontinuation, caution in patients with concomitant use of nephrotoxic agents.
Adverse Reactions - Common
- Nasal symptoms (nasopharyngitis, URI) (Common)
- Headache (Common)
- Fatigue (Common)
- Nausea (Common)
- Elevated liver enzymes (Common)
Adverse Reactions - Serious
- Lactic acidosis and severe hepatomegaly with steatosis (Rare)
- Renal impairment including Fanconi syndrome (Rare)
- Bone mineral density loss (Rare)
Drug-Drug Interactions
- Rifampin, atazanavir, other nephrotoxic or nephrotoxic agents
Drug-Food Interactions
N/ADrug-Herb Interactions
N/ANursing Implications
Assessment: Monitor renal function (serum creatinine, estimated glomerular filtration rate). Monitor bone density in long-term therapy.
Diagnoses:
- Risk for renal impairment
- Risk for decreased bone density
Implementation: Ensure appropriate renal function monitoring, educate patient on hydration, assess for symptoms of adverse effects.
Evaluation: Renal function remains stable, symptoms of adverse effects are minimized or absent.
Patient/Family Teaching
- Take medication as directed, with or without food.
- Report symptoms of renal impairment (e.g., swelling, fatigue).
- Maintain hydration.
- Do not discontinue abruptly, especially in HBV patients, to prevent flare-ups.
Special Considerations
Black Box Warnings:
- Risk of hepatitis B flare upon discontinuation, which can be severe and sometimes fatal.
Genetic Factors: N/A
Lab Test Interference: May cause elevations in serum creatinine and phosphate levels, monitor accordingly.
Overdose Management
Signs/Symptoms: Potential overdose may cause nausea, vomiting, renal impairment, lactic acidosis.
Treatment: Supportive care; hemodialysis may be considered in severe cases.
Storage and Handling
Storage: Store at room temperature 20°C to 25°C (68°F to 77°F); protect from light and moisture.
Stability: Stable under recommended storage conditions.