Usage
- Medical Conditions: Emtricitabine + Tenofovir Alafenamide is prescribed in combination with other antiretroviral agents for the treatment of Human Immunodeficiency Virus type 1 (HIV-1) infection in adults and adolescents (aged 12 years and older with body weight at least 35 kg). It is also indicated for pre-exposure prophylaxis (PrEP) to reduce the risk of HIV-1 infection in individuals at high risk. It is not indicated for the treatment of chronic hepatitis B virus (HBV) infection.
- Pharmacological Classification: Antiretroviral, Nucleoside/Nucleotide Reverse Transcriptase Inhibitor (NRTI).
- Mechanism of Action: Both emtricitabine and tenofovir alafenamide are nucleoside/nucleotide reverse transcriptase inhibitors. They are phosphorylated intracellularly to their active metabolites, which compete with natural substrates and incorporate into viral DNA, causing chain termination. This inhibits the reverse transcription of viral RNA into DNA, thereby blocking HIV-1 replication.
Alternate Names
- Emtricitabine/Tenofovir alafenamide fumarate
- FTC/TAF
- Brand Name: Descovy®
How It Works
- Pharmacodynamics: Emtricitabine and tenofovir alafenamide interfere with viral replication within infected cells. The active metabolites compete with natural substrates and get incorporated into the growing viral DNA chain, causing its termination. This prevents the formation of new HIV-1 virions. Emtricitabine’s active form is emtricitabine triphosphate, and tenofovir alafenamide’s active form is tenofovir diphosphate.
- Pharmacokinetics:
- Absorption: Tenofovir alafenamide is a prodrug that is rapidly hydrolyzed to tenofovir after oral administration. Both drugs are well absorbed.
- Metabolism: Tenofovir alafenamide is metabolized to tenofovir. Emtricitabine is minimally metabolized.
- Elimination: Both drugs are primarily excreted renally, with a small amount excreted in the feces.
Dosage
Standard Dosage
Adults (HIV-1 Treatment):
- 200 mg emtricitabine/25 mg tenofovir alafenamide orally once daily with or without food.
Adults (PrEP):
- 200 mg emtricitabine/25 mg tenofovir alafenamide orally once daily with or without food.
Children (HIV-1 Treatment, age 12 years and older and weighing at least 35 kg):
- 200 mg emtricitabine/25 mg tenofovir alafenamide orally once daily with or without food.
Children (PrEP, age 12 years and older and weighing at least 35 kg):
- 200 mg emtricitabine/25 mg tenofovir alafenamide orally once daily.
Children (PrEP, weighing less than 35 kg): Use and dose must be determined by a doctor. Specific recommendations for children based on weight brackets:
- 25kg to <35kg: 200mg/25mg once daily.
- 14kg to <25kg: 120mg/15mg once daily.
Special Cases:
-
Elderly Patients: No dose adjustment is generally required.
-
Patients with Renal Impairment: Dosage adjustments may be necessary. Not recommended for creatinine clearance (CrCl) below 30 mL/min for treatment. For CrCl 15 to <30 mL/min: Not recommended for treatment. CrCl <15 mL/min on hemodialysis: One tablet once daily on hemodialysis days, after completion. Consult specific guidance.
-
Patients with Hepatic Dysfunction: No dosage adjustment is generally required for mild to moderate hepatic impairment.
-
Patients with Comorbid Conditions: Assess for potential drug interactions and adjust dosages as needed.
Clinical Use Cases
These use cases do not usually involve dose or administration changes for this combination. Standard dosing guidelines are typically followed in these clinical settings, with consideration of patient-specific factors as described above.
- Intubation
- Surgical Procedures
- Mechanical Ventilation
- Intensive Care Unit (ICU) Use
- Emergency Situations
Side Effects
Common Side Effects
- Nausea
- Diarrhea
- Headache
- Fatigue
- Abdominal Pain
Rare but Serious Side Effects
- Lactic acidosis
- Hepatotoxicity (liver damage)
- Renal impairment (kidney problems)
- Bone density changes (with chronic use)
- Allergic reactions
- New onset or worsening of HBV infection upon discontinuation
Contraindications
- Hypersensitivity to emtricitabine, tenofovir alafenamide, or any component of the formulation.
- Severe renal impairment (CrCl < 30 mL/min).
- Coadministration with other medications containing tenofovir disoproxil fumarate.
Drug Interactions
- Drugs that induce P-glycoprotein (P-gp) or CYP3A4 may reduce tenofovir alafenamide concentrations.
- Drugs that inhibit P-gp may increase tenofovir alafenamide concentrations.
- Coadministration with other nephrotoxic drugs may increase the risk of renal impairment.
- Some examples include: rifampin, rifabutin, oxcarbazepine, phenytoin, phenobarbital, St. John’s wort, atazanavir, lopinavir/ritonavir, and high-dose or multiple non-steroidal anti-inflammatory drugs (NSAIDs).
Pregnancy and Breastfeeding
- Pregnancy: Insufficient data available on tenofovir alafenamide in pregnant women to inform a drug-related risk. Emtricitabine/tenofovir disoproxil fumarate has shown no increased risk of birth defects in limited studies. Consult latest guidance and consider risks and benefits.
- Breastfeeding: Not recommended due to the potential for HIV-1 transmission through breast milk. Data shows components of the drug being present in human milk.
Drug Profile Summary
- Mechanism of Action: Nucleoside/Nucleotide Reverse Transcriptase Inhibitors (NRTIs); inhibit HIV-1 reverse transcription by causing DNA chain termination.
- Side Effects: Nausea, diarrhea, headache, fatigue, abdominal pain, lactic acidosis (rare), hepatotoxicity (rare), renal impairment (rare).
- Contraindications: Hypersensitivity, severe renal impairment, concomitant use with tenofovir disoproxil fumarate.
- Drug Interactions: P-gp inducers/inhibitors, CYP3A4 inducers, nephrotoxic drugs.
- Pregnancy & Breastfeeding: Limited safety data in pregnancy; breastfeeding not recommended.
- Dosage: 200 mg/25 mg once daily for treatment and PrEP in adults and adolescents (12 years and older, weighing at least 35kg). Dosage adjustment may be needed based on renal function.
- Monitoring Parameters: Renal function, liver function tests, HIV-1 viral load, CD4 count, bone mineral density (with long-term use).
Popular Combinations
Emtricitabine/Tenofovir alafenamide is commonly combined with integrase strand transfer inhibitors (INSTIs) such as dolutegravir or bictegravir, or with non-nucleoside reverse transcriptase inhibitors (NNRTIs) like rilpivirine, or protease inhibitors boosted with ritonavir or cobicistat like atazanavir, darunavir, lopinavir.
Precautions
- General Precautions: Assess for renal function, liver function, and HBV infection status before starting treatment. Monitor for adverse effects during treatment.
- Specific Populations: See “Special Cases” under “Dosage.”
- Lifestyle Considerations: Excessive alcohol use may increase the risk of liver and pancreatic side effects.
FAQs (Frequently Asked Questions)
Q1: What is the recommended dosage for Emtricitabine + Tenofovir Alafenamide?
A: The standard dosage is 200 mg emtricitabine/25 mg tenofovir alafenamide taken orally once daily, with or without food. Dosage adjustments may be necessary based on renal function and other factors. See “Dosage” section for details.
Q2: What are the most common side effects of Emtricitabine + Tenofovir Alafenamide?
A: Nausea, diarrhea, headache, and fatigue are the most commonly reported side effects.
Q3: What are the serious side effects of Emtricitabine + Tenofovir Alafenamide?
A: Serious side effects, while rare, include lactic acidosis, hepatotoxicity, renal impairment, and bone density changes. Patients should be monitored for these potential complications.
Q4: Can Emtricitabine + Tenofovir Alafenamide be used during pregnancy?
A: Data on tenofovir alafenamide during pregnancy is limited. The risks and benefits should be carefully considered. Consult the latest guidelines.
Q5: Can Emtricitabine + Tenofovir Alafenamide be used during breastfeeding?
A: Breastfeeding is not recommended due to potential for HIV transmission.
Q6: Does Emtricitabine + Tenofovir Alafenamide interact with other medications?
A: Yes, several clinically significant drug interactions are possible. See the “Drug Interactions” section for details. Always assess for potential interactions before co-prescribing.
Q7: What should be monitored in patients taking Emtricitabine + Tenofovir Alafenamide?
A: Monitor renal function, liver function tests, HIV-1 viral load, and CD4 counts. Bone mineral density should be assessed with long-term use.
Q8: Can Emtricitabine + Tenofovir Alafenamide cure HIV?
A: No, Emtricitabine + Tenofovir Alafenamide is not a cure for HIV. It is used to suppress viral replication and slow disease progression.
Q9: Can Emtricitabine + Tenofovir Alafenamide be used alone to treat HIV?
A: No, Emtricitabine + Tenofovir Alafenamide should always be used in combination with other antiretroviral medications for the treatment of HIV-1 infection.
