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Tenofovir Mechanism Of Action

Tenofovir Mechanism Of Action


Tafnat 25mg (Tenofovir Alafenamide -TAF) 25mg (TAF) is a Nucleotide Reverse Transcriptase Inhibitor (NRTI) and a novel ester prodrug of the antiretroviral,tenofovir.

Following oral administration, Tafnat 25mg (Tenofovir alafenamide -TAF) (TAF) is converted in vivo to tenofovir. An acyclic nucleoside phosphonate (nucleotide) analog of adenosine 5'-monophosphate. Tenofovir alafenamide 25mg Tablets mimics normal DNA building blocks but is lacking a 3'-OH molecule required for phosphodiester bond linkage.

A competing TAF with regular nucleotides for incorporation into the proviral DNA and prevention of the formation of 5 to 3 tenofovir tablets. A phosphodiester linkage required for DNA elongation.

Tafnat 25mg (Tenofovir Alafenamide -TAF) tablets causes early chain termination and prevents proviral DNA 27 transcription.

Warnings and Precautions

Risk of Development of HIV-1 Resistance in HBV/HIV-1 Coinfected Patients: Due to this risk, VEMLIDY alone should not be used for the treatment of HIV-1 infection. Safety and efficacy of VEMLIDY have not been established in HBV/HIV-1 coinfected patients. HIV antibody testing should be offered to all HBV-infected patients before initiating therapy with VEMLIDY, and, if positive, an appropriate antiretroviral combination regimen that is recommended for HBV/HIV-1 coinfected patients should be used.

New Onset or Worsening Renal Impairment: Cases of acute renal failure and Fanconi syndrome have been reported with the use of tenofovir prodrugs.

In clinical trials of VEMLIDY, there have been no cases of Fanconi syndrome or proximal renal tubulopathy (PRT). Patients with impaired renal function and/or taking nephrotoxic agents (including NSAIDs) are at increased risk of renal-related adverse reactions. Discontinue VEMLIDY in patients who develop clinically significant decreases in renal function or evidence of Fanconi syndrome. Monitor renal function in all patients – See Dosage and Administration.

Lactic Acidosis and Severe Hepatomegaly with Steatosis: Fatal cases have been reported with the use of nucleoside analogs, including tenofovir DF.

Discontinue VEMLIDY if clinical or laboratory findings suggestive of lactic acidosis or pronounced hepatotoxicity develop, including hepatomegaly and steatosis in the absence of marked transaminase elevations.

Drug Interactions

Coadministration of VEMLIDY with drugs that reduce renal function or compete for active tubular secretion may increase concentrations of tenofovir and the risk of adverse reactions.

Coadministration of VEMLIDY is not recommended with the following: oxcarbazepine, phenobarbital, phenytoin, rifabutin, rifampin, rifapentine, or St. John’s wort. Such coadministration is expected to decrease the concentration of tenofovir alafenamide, reducing the therapeutic effect of VEMLIDY. Drugs that strongly affect P-glycoprotein (P-gp) and breast cancer resistance protein (BCRP) activity may lead to changes in VEMLIDY absorption.

Consult the full prescribing information for VEMLIDY for more information on potentially significant drug interactions, including clinical comments.

Dosage and Administration

  • Dosage: Adults; 1 tablet taken once daily with food.
  • Renal Impairment, Screening, and Monitoring: VEMLIDY is not recommended in patients with CrCl <15 mL/min. In all patients, assess serum creatinine, estimated creatinine clearance, urine glucose, and urine protein prior to initiating and during treatment, on a clinically appropriate schedule. In patients with chronic kidney disease, also assess serum phosphorus.
  • Hepatic Impairment: Not recommended in patients with decompensated (Child-Pugh B or C) hepatic impairment.
  • Testing Prior to Initiation: HIV infection.

Storage and Handling :

  • 28 Store below 30°C (86°F).
  • Keep container tightly closed.
  • Dispense only in original container.

Post Treatment Exacerbation of Hepatitis B Infection

Discontinuation of Tafnat25mg (Tenofovir Alafenamide Fumarate -TAF) may result in severe acute exacerbations of hepatitis B. Hepatic function should be monitored closely with both clinical and laboratory follow-up for at least several months in patients who discontinue of (Tenofovir alafenamide -TAF) tablets.

Risk of Development of HIV-1 Resistance in Patients Co-infected with HBV and HIV-1

Tafnat 25mg (Tenofovir Alafenamide Fumarate -TAF) alone is not recommended for the treatment of HIV-1 infection, as there is a risk of development of HIV-1 resistance. In patients co-infected with HBV and HIV-1, efficacy of TAF has not been established. Prior to initiating the therapy with Tafnat 25mg (Tenofovir Alafenamide -TAF) in patients with HBV-HIV co-infected patients, HIV antibody testing should be offered and, if positive, an appropriate antiretroviral combination regimen that is recommended for patients coinfected with HIV-1 should be used.

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