What it's for (Indications)
- Tenofovir alafenamide (TAF) is indicated for the treatment of specific viral infections.
- For human immunodeficiency virus type 1 (HIV-1) infection, TAF is approved for use in adults and pediatric patients weighing at least 14 kg, as a component of a complete antiretroviral regimen.
- It is crucial to note that TAF must always be co-administered with other antiretroviral agents and is not indicated as a monotherapy for HIV-1.
- The use of TAF in HIV-1 treatment is supported by its potent antiviral activity and generally improved safety profile compared to its predecessor, tenofovir disoproxil fumarate (TDF), particularly concerning renal and bone mineral density outcomes.
- Furthermore, TAF is indicated for the treatment of chronic hepatitis B virus (HBV) infection in adults and pediatric patients aged 12 years and older with compensated liver disease.
- Its efficacy against both HIV-1 and HBV stems from its unique pharmacology that allows for efficient intracellular delivery of tenofovir, minimizing systemic exposure while maximizing antiviral effect.
- These indications are based on robust clinical trials demonstrating significant viral suppression and clinical benefits in the respective patient populations, contributing to improved long-term health outcomes for individuals living with these chronic viral infections.
Dosage Information
| Type | Guideline |
|---|---|
| Standard | The recommended dosage of tenofovir alafenamide (TAF) varies slightly depending on the indication and specific patient characteristics. For the treatment of HIV-1 infection, the standard adult and pediatric dosage (for patients weighing at least 35 kg) is 25 mg once daily, administered orally, typically as part of a fixed-dose combination product containing other antiretroviral agents. For pediatric patients weighing 14 kg to less than 35 kg, the recommended dose is 10 mg once daily. For the treatment of chronic hepatitis B virus (HBV) infection in adults and pediatric patients aged 12 years and older weighing at least 35 kg, the recommended dose is 25 mg once daily, administered orally. It is imperative that TAF be taken with food to enhance its bioavailability and ensure optimal drug exposure. No dosage adjustment is generally required for patients with mild, moderate, or severe renal impairment (creatinine clearance ≥ 15 mL/min), or for patients with end-stage renal disease (ESRD) on hemodialysis, on dialysis days following completion of hemodialysis. However, TAF is not recommended in patients with ESRD who are not on hemodialysis. For patients with impaired hepatic function, no dosage adjustment is necessary for mild or moderate hepatic impairment (Child-Pugh A or B), but TAF has not been studied in patients with decompensated hepatic impairment (Child-Pugh C). |
Safety & Warnings
Common Side Effects
- While tenofovir alafenamide (TAF) generally demonstrates a favorable safety profile compared to tenofovir disoproxil fumarate (TDF), a range of side effects can occur, necessitating patient education and vigilant monitoring.
- Common adverse reactions reported in clinical trials, often mild to moderate in severity, include gastrointestinal disturbances such as nausea, diarrhea, abdominal pain, and flatulence, along with headache and fatigue.
- More serious but less common side effects require careful clinical consideration.
- These can include new onset or worsening renal impairment, although the risk is significantly lower than with TDF due to reduced systemic tenofovir exposure.
- Patients may experience modest decreases in bone mineral density, though the impact on bone health is also generally less pronounced than with TDF.
- Other important potential adverse effects, though rare, include lactic acidosis and severe hepatomegaly with steatosis, conditions that can be life-threatening and demand immediate medical intervention.
- Additionally, in patients with HIV-1, an immune reconstitution inflammatory syndrome (IRIS) can occur following initiation of combination antiretroviral therapy (cART), including TAF, where the immune system responds vigorously to previously subclinical opportunistic infections.
- Regular monitoring of renal function, bone health parameters, and liver enzymes is crucial throughout TAF therapy to promptly identify and manage any emerging adverse effects.
Serious Warnings
- Black Box Warning: **WARNING: SEVERE ACUTE EXACERBATIONS OF HEPATITIS B AND LACTIC ACIDOSIS/SEVERE HEPATOMEGALY WITH STEATOSIS** * **Severe Acute Exacerbations of Hepatitis B:** Discontinuation of tenofovir alafenamide (TAF) in patients co-infected with human immunodeficiency virus type 1 (HIV-1) and chronic hepatitis B virus (HBV) infection may lead to severe acute exacerbations of hepatitis B. Patients co-infected with HIV-1 and HBV should be closely monitored with both clinical and laboratory follow-up for at least several months after discontinuing TAF. In some cases, these exacerbations have been associated with hepatic decompensation and liver failure. Resumption of anti-HBV therapy may be warranted. * **Lactic Acidosis and Severe Hepatomegaly with Steatosis:** Lactic acidosis and severe hepatomegaly with steatosis, including fatal cases, have been reported with the use of nucleoside analogs, including tenofovir disoproxil fumarate (TDF), a related antiretroviral. While TAF has a significantly lower systemic exposure to tenofovir compared to TDF, this serious warning remains relevant for the class of drugs. Treatment with TAF should be suspended in any patient who develops clinical or laboratory findings suggestive of lactic acidosis or pronounced hepatotoxicity (which may include hepatomegaly and steatosis even in the absence of marked transaminase elevations). These adverse events, though rare, can be life-threatening and require immediate medical intervention.
- Several critical warnings must be meticulously considered when prescribing or administering tenofovir alafenamide (TAF) to ensure patient safety and optimize treatment outcomes.
- Patients co-infected with HIV-1 and chronic hepatitis B virus (HBV) infection are at risk of severe acute exacerbations of hepatitis B if TAF is discontinued; therefore, they should be vigilantly monitored with both clinical and laboratory follow-up for at least several months after cessation of therapy, as these exacerbations can lead to hepatic decompensation and failure.
- TAF is not approved as monotherapy for HIV-1 infection, and patients co-infected with HIV-1 and HBV must always receive a complete antiretroviral regimen for HIV-1.
- Lactic acidosis and severe hepatomegaly with steatosis, including fatal cases, have been reported with nucleoside analogs, and while TAF has lower systemic tenofovir exposure, this risk, though rare, necessitates caution and immediate suspension of TAF if suspected.
- New onset or worsening renal impairment, including acute renal failure, has been reported; thus, renal function should be assessed prior to and regularly during therapy.
- Although TAF has a better renal and bone safety profile than TDF, decreases in bone mineral density have occurred.
- Immune reconstitution inflammatory syndrome (IRIS) may develop in HIV-infected patients initiating antiretroviral therapy, requiring appropriate diagnostic evaluation and treatment.
- Caution is advised when coadministering TAF with other nephrotoxic agents or drugs that significantly affect the activity of P-glycoprotein and breast cancer resistance protein (BCRP), as this could alter TAF exposure and potentially increase the risk of adverse reactions.
How it Works (Mechanism of Action)
Tenofovir alafenamide (TAF) functions as a highly potent and selective prodrug of tenofovir, classified as a nucleotide reverse transcriptase inhibitor (NtRTI). Upon oral administration, TAF is efficiently absorbed and then predominantly hydrolyzed within target cells, particularly lymphoid cells (for HIV-1) and hepatocytes (for HBV), to form the active antiviral agent, tenofovir. This targeted intracellular delivery mechanism results in significantly lower systemic plasma concentrations of tenofovir compared to tenofovir disoproxil fumarate (TDF), thereby mitigating the systemic side effects, particularly renal and bone toxicities. Once inside the cells, tenofovir is subsequently phosphorylated by cellular kinases to its active metabolite, tenofovir diphosphate. This diphosphate form is a highly selective and competitive inhibitor of both HIV-1 reverse transcriptase and HBV DNA polymerase. It competes with the natural substrate deoxyadenosine triphosphate for incorporation into the nascent viral DNA chain. Upon incorporation, tenofovir diphosphate causes premature DNA chain termination, effectively halting viral DNA synthesis and replication. This optimized intracellular activation and targeted delivery contribute to TAF's enhanced antiviral potency at lower doses and its improved safety profile by maximizing intracellular concentrations where the drug is needed for antiviral effect while minimizing extracellular tenofovir exposure.
Commercial Brands (Alternatives)
No other brands found for this formula.