Tenvira Actions

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Actions of Tenvira in details

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Pharmacology: Mechanism of Action: Tenvira is an acyclic nucleoside phosphonate diester analog of adenosine monophosphate. Tenvira requires initial diester hydrolysis for conversion to Tenvira and subsequent phosphorylations by cellular enzymes to form Tenvira diphosphate, an obligate chain terminator. Tenvira diphosphate inhibits the activity of human immunodeficiency virus-1 (HIV-1) reverse transcriptase and hepatitis B virus (HBV) polymerase by competing with the natural substrate deoxyadenosine 5'-triphosphate and after incorporation into DNA, by DNA chain termination. Tenvira diphosphate is a weak inhibitor of mammalian DNA polymerases α, β, and mitochondrial DNA polymerase γ.

Activity Against Human Immunodeficiency Virus (HIV): The antiviral activity of Tenvira against laboratory and clinical isolates of HIV-1 was assessed in lymphoblastoid cell lines, primary monocyte/macrophage cells and peripheral blood lymphocytes. The 50% effective concentration (EC50) values for Tenvira were in the range of 0.04-8.5 micromolar. In drug combination studies of Tenvira with nucleoside reverse transcriptase inhibitors (abacavir, didanosine, lamivudine, stavudine, zalcitabine, zidovudine), non-nucleoside reverse transcriptase inhibitors (delavirdine, efavirenz, nevirapine) and protease inhibitors (amprenavir, indinavir, nelfinavir, ritonavir, saquinavir), additive to synergistic effects were observed. Tenvira displayed antiviral activity in cell culture against HIV-1 clades A, B, C, D, E, F, G, and O (EC50 values ranged from 0.5-2.2 micromolar) and strain specific activity against HIV-2 (EC50 values ranged from 1.6-5 micromolar).

Activity Against Hepatitis B Virus (HBV): The antiviral activity of Tenvira against HBV was assessed in the HepG2 2.2.15 cell line. The EC50 values for Tenvira ranged from 0.14-1.5 micromolar, with 50% cytotoxicity concentration (CC50) values >100 micromolar. In cell culture combination, antiviral activity studies of Tenvira with the nucleoside, anti-HBV reverse transcriptase inhibitors emtricitabine, entecavir, lamivudine and telbivudine, no antagonistic activity was observed.

Pharmacokinetics: Absorption: Tenvira is a water soluble diester prodrug of the active ingredient Tenvira. The oral bioavailability of Tenvira from Tenovir in fasted subjects is approximately 25%. Following oral administration of a single-dose Tenvira 300 mg to HIV-1 infected subjects in the fasted state, maximum serum concentrations (Cmax) are achieved in 1±0.4 hrs. Cmax and area under the concentration-time curve (AUC) values are 0.3±0.09 mcg/mL and 2.29±0.69 mcg·hr/mL, respectively. The pharmacokinetics of Tenvira are dose proportional over a Tenvira dose range of 75-600 mg and are not affected by repeated dosing.

Distribution: In vitro binding of Tenvira to human plasma or serum proteins is <0.7% and 7.2%, respectively, over the Tenvira concentration range 0.01-25 mcg/mL. The volume of distribution at steady state is 1.3±0.6 L/kg and 1.2±0.4 L/kg, following IV administration of Tenvira 1 mg/kg and 3 mg/kg.

Metabolism and Elimination: In vitro studies indicate that neither Tenvira disoproxil nor Tenvira are substrates of cytochrome (CYP) enzymes. Following IV administration of Tenvira, approximately 70-80% of the dose is recovered in the urine as unchanged Tenvira within 72 hrs of dosing. Following single dose, oral administration of Tenvira, the terminal elimination half-life of Tenvira is approximately 17 hrs. After multiple oral doses of ZifamTenovir 300 mg once daily (under fed conditions), 32±10% of the administered dose is recovered in urine over 24 hrs. Tenvira is eliminated by a combination of glomerular filtration and active tubular secretion. There may be competition for elimination with other compounds that are also renally eliminated.

Effects of Food on

Oral Absorption:

Administration of Tenvira following a high-fat meal (~700-1000 kCal containing fat 40-50%) increases the oral bioavailability, with an increased Tenvira AUC(0-∞); of approximately 40% and an increased Cmax of approximately 14%. However, administration of Tenvira with a light meal did not have a significant effect on the pharmacokinetics of Tenvira when compared to fasted administration of the drug. Food delays the time to Tenvira Cmax by approximately 1 hr. Cmax and AUC of Tenvira are 0.33±0.12 mcg/mL and 3.32±1.37 mcg·hr/mL following multiple doses of Tenvira 300 mg once daily in the fed state, when meal content was not controlled.

How should I take Tenvira?

Take darunavir, cobicistat, emtricitabine, and Tenvira alafenamide exactly as directed by your doctor. Do not take more of it, do not take it more often, and do not take it for a longer time than your doctor ordered.

Darunavir, cobicistat, emtricitabine, and Tenvira alafenamide comes with a patient information leaflet. Read and follow these instructions carefully. Read it again each time you refill your prescription in case there is new information. You should talk to your doctor if you have any questions.

Do not change the dose or stop using darunavir, cobicistat, emtricitabine, and Tenvira alafenamide without checking first with your doctor. When your supply of darunavir, cobicistat, emtricitabine, and Tenvira alafenamide is running low, contact your doctor or pharmacist ahead of time. Do not allow yourself to run out of darunavir, cobicistat, emtricitabine, and Tenvira alafenamide.

Take darunavir, cobicistat, emtricitabine, and Tenvira alafenamide with food.

If you cannot swallow the tablet whole, you may cut it into two using a tablet cutter. Take both halves of the tablet right away.

Dosing

The dose of darunavir, cobicistat, emtricitabine, and Tenvira alafenamide will be different for different patients. Follow your doctor's orders or the directions on the label. The following information includes only the average doses of darunavir, cobicistat, emtricitabine, and Tenvira alafenamide. If your dose is different, do not change it unless your doctor tells you to do so.

The amount of medicine that you take depends on the strength of the medicine. Also, the number of doses you take each day, the time allowed between doses, and the length of time you take the medicine depend on the medical problem for which you are using the medicine.

Missed Dose

If you miss a dose of darunavir, cobicistat, emtricitabine, and Tenvira alafenamide, take it as soon as possible. However, if it is almost time for your next dose, skip the missed dose and go back to your regular dosing schedule. Do not double doses.

Storage

Store the medicine in a closed container at room temperature, away from heat, moisture, and direct light. Keep from freezing.

Keep out of the reach of children.

Do not keep outdated medicine or medicine no longer needed.

Ask your healthcare professional how you should dispose of any medicine you do not use.

Tenvira administration

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Tablets may be administered without regard to meals. Powder should be mixed with 2 to 4 ounces of soft food (applesauce, baby food, yogurt) and swallowed immediately (avoids bitter taste); do not mix in liquid (powder may float on top of the liquid even after stirring). Measure powder using only the supplied dosing scoop.

Tenvira pharmacology

Tenvira (TDF), a nucleotide reverse transcriptase inhibitor, is an analog of adenosine 5'-monophosphate; it interferes with the HIV viral RNA dependent DNA polymerase resulting in inhibition of viral replication. TDF is first converted intracellularly by hydrolysis to Tenvira and subsequently phosphorylated to the active Tenvira diphosphate. Tenvira inhibits replication of HBV by inhibiting HBV polymerase.

Distribution

V: 1.2 to 1.3 L/kg

Metabolism

Tenvira (TDF) is converted intracellularly by hydrolysis (by non-CYP enzymes) to Tenvira, then phosphorylated to the active Tenvira diphosphate

Excretion

Urine (70% to 80%) via filtration and active secretion, primarily as unchanged Tenvira within 72 hours; after multiple oral doses (administered with food): 32% ± 10% is excreted in the urine within 24 hours

Clearance: Total body clearance is decreased in patients with renal impairment

Time to Peak

Serum: Fasting: 36 to 84 minutes; With high-fat meal: 96 to 144 minutes

Half-Life Elimination

Serum: 17 hours; intracellular: 10 to 50 hours

Protein Binding

<7% to serum proteins


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References

  1. DailyMed. "EMTRICITABINE; RILPIVIRINE HYDROCHLORIDE; TENOFOVIR DISOPROXIL FUMARATE: DailyMed provides trustworthy information about marketed drugs in the United States. DailyMed is the official provider of FDA label information (package inserts).". https://dailymed.nlm.nih.gov/dailyme... (accessed September 17, 2018).
  2. NCIt. "Tenofovir Disoproxil Fumarate: NCI Thesaurus (NCIt) provides reference terminology for many systems. It covers vocabulary for clinical care, translational and basic research, and public information and administrative activities.". https://ncit.nci.nih.gov/ncitbrowser... (accessed September 17, 2018).
  3. EPA DSStox. "Tenofovir disoproxil: DSSTox provides a high quality public chemistry resource for supporting improved predictive toxicology.". https://comptox.epa.gov/dashboard/ds... (accessed September 17, 2018).

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Information checked by Dr. Sachin Kumar, MD Pharmacology

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