TENOFENAMIDE 25 MG (TENOFOVIR ALAFENAMIDE) – MEDICAL DESCRIPTION

Antiviral Medication | Chronic Hepatitis B Management

TENOFENAMIDE 25 MG contains Tenofovir Alafenamide (TAF), an antiviral medication belonging to the nucleotide reverse transcriptase inhibitor (NtRTI) class. It is primarily used for the treatment of chronic hepatitis B virus (HBV) infection.

Tenofovir alafenamide is a prodrug of tenofovir that is converted into its active form inside cells, where it inhibits viral replication. Compared with the older formulation, tenofovir disoproxil fumarate (TDF), TAF achieves effective intracellular drug concentrations with lower circulating tenofovir exposure, which may offer advantages regarding kidney and bone safety.

Composition and Pharmaceutical Form

Drug classification: Antiviral – Nucleotide Reverse Transcriptase Inhibitor (NtRTI).

Indications and Uses

TENOFENAMIDE 25 MG is primarily indicated for:

• Chronic Hepatitis B (HBV): Helps suppress hepatitis B viral replication and reduce viral activity in patients with chronic HBV infection.
• Viral Load Reduction: Helps decrease HBV DNA levels in the blood, supporting long-term viral suppression.
• Liver Disease Management: Helps reduce ongoing viral activity that contributes to liver inflammation and damage.
• Prevention of Disease Progression: Sustained viral suppression may reduce the risk of complications associated with chronic hepatitis B, including liver fibrosis, cirrhosis, and hepatocellular carcinoma.

Important indication clarification: Tenofovir alafenamide 25 mg as a single-agent formulation is used for chronic hepatitis B. It is not an adequate stand-alone treatment for HIV infection. In patients with HIV/HBV coinfection, it must be incorporated into an appropriate, fully suppressive HIV treatment regimen.

Mechanism of Action

Tenofovir alafenamide works by inhibiting the replication of hepatitis B virus.

Its mechanism involves:

1. Cellular Activation: Tenofovir alafenamide enters cells and is converted into its active metabolite, tenofovir diphosphate.
2. Enzyme Inhibition: The active metabolite inhibits HBV DNA polymerase, an essential enzyme involved in viral replication.
3. DNA Chain Termination: It competes with natural nucleotides and becomes incorporated into viral DNA, resulting in premature termination of DNA chain formation.
4. Viral Suppression: This reduces the ability of HBV to multiply, helping decrease viral load and control chronic infection.

Important: Tenofovir alafenamide suppresses HBV replication but does not necessarily eliminate the virus or provide a complete cure.

Dosage and Method of Administration

• Recommended adult dose: One 25 mg tablet once daily.
• Take the tablet orally with food.
• Swallow the tablet whole with water.
• Take the medication at approximately the same time each day.
• If a dose is missed, take it as soon as possible on the same day. If it is almost time for the next dose, skip the missed dose and continue the regular schedule.
• Do not take two doses together to compensate for a missed dose.

Duration of treatment: Treatment is generally long-term and depends on the patient's virological response, liver condition, and physician's assessment.

Important: Do not discontinue treatment without medical supervision, as stopping tenofovir alafenamide may cause a severe flare-up of hepatitis B.

TENOFENAMIDE is generally well tolerated. However, some patients may experience adverse effects.

Common or reported side effects:

• Headache.
• Abdominal pain.
• Nausea.
• Fatigue.
• Diarrhea.
• Back pain.
• Cough.

Potentially serious adverse effects:

• Kidney problems: Although TAF generally has a more favorable renal safety profile than TDF, kidney impairment and renal tubular abnormalities may still occur.
• Lactic Acidosis: A rare but serious condition involving excessive lactic acid accumulation in the blood.
• Severe Hepatomegaly with Steatosis: Rare enlargement of the liver associated with fat accumulation.
• Hepatitis B Exacerbation: Severe worsening of hepatitis B may occur following discontinuation of treatment.

Seek immediate medical attention if unusual muscle weakness, persistent nausea, abdominal discomfort, difficulty breathing, or signs of significant liver deterioration occur.

There are no specific formal contraindications listed in the U.S. prescribing information for tenofovir alafenamide 25 mg. However, important precautions should be considered.

Special precautions:

• Renal Impairment: Assess kidney function before and during treatment, including serum creatinine, estimated creatinine clearance, urine glucose, and urine protein.
• Hepatic Impairment: Not recommended for patients with decompensated liver disease (Child-Pugh B or C) under the U.S. product labeling.
• HIV Infection: Patients should be tested for HIV before starting treatment. Tenofovir alafenamide alone should not be used to treat HIV infection.
• Treatment Discontinuation: Stopping therapy may cause severe acute exacerbation of hepatitis B. Patients require close clinical and laboratory monitoring after discontinuation.
• Bone Health: Patients with underlying osteoporosis or other risk factors for bone disease should discuss appropriate monitoring with their physician.
• Liver Monitoring: Periodic assessment of liver function and HBV viral markers is important during treatment.

Drug Interactions

Tenofovir alafenamide is a substrate of P-glycoprotein (P-gp) and breast cancer resistance protein (BCRP). Medications that strongly affect these transport proteins may alter its absorption and effectiveness.

Important interactions include:

• Rifampicin: May reduce tenofovir alafenamide exposure and antiviral effectiveness.
• Rifabutin and Rifapentine: May decrease drug concentrations.
• Certain Anticonvulsants: Carbamazepine, oxcarbazepine, phenobarbital, and other enzyme-inducing medications may reduce exposure.
• St. John's Wort: May decrease tenofovir alafenamide concentrations.
• Nephrotoxic Medications: Certain medicines that affect kidney function may increase the risk of renal adverse effects.

Patients should inform their physician or pharmacist about all prescription medications, over-the-counter products, and herbal supplements they are taking.

Pregnancy and Breastfeeding

• Pregnancy: Treatment decisions should be made by a healthcare professional after evaluating the potential benefits and risks. Women with chronic hepatitis B should receive appropriate medical monitoring during pregnancy.
• Breastfeeding: Consult a physician before using this medication while breastfeeding, particularly when considering maternal HBV infection and infant prevention measures.

Storage Conditions

• Store at room temperature according to the manufacturer's instructions.
• Keep in the original packaging to protect the tablets from moisture.
• Store in a dry place away from direct sunlight and excessive heat.
• Keep the container tightly closed.
• Keep out of reach of children.
• Do not use after the expiry date.

Patient Disclaimer

This description is intended for educational and informational purposes only. It does not replace professional medical advice, diagnosis, or treatment.

TENOFENAMIDE 25 MG should only be used under the supervision of a qualified healthcare professional. Patients should follow the prescribed dosage and undergo regular medical and laboratory monitoring during treatment.

Do not stop taking this medication without consulting your physician, as discontinuation may lead to a serious worsening of hepatitis B infection.

References

1. U.S. FDA – DailyMed: Official prescribing information for tenofovir alafenamide 25 mg, including indications, dosage, contraindications, warnings, and adverse reactions. Vemlidy – FDA/DailyMed.
2. U.S. National Institutes of Health (NIH): Drug information and FDA labeling for tenofovir alafenamide. Tenofovir Alafenamide – NIH.
3. University of Washington – Hepatitis B Online: Clinical pharmacology, indications, safety, and clinical use of tenofovir alafenamide in chronic hepatitis B. Tenofovir Alafenamide – Hepatitis B Online.
4. NIH Clinical Guidelines: Recommendations for the management of hepatitis B and HIV coinfection. HBV/HIV Coinfection – NIH Guidelines.
5. FDA-Verified Product Information: Tenofovir alafenamide 25 mg film-coated tablets, including composition and clinical particulars. Tenofovir Alafenamide – Product Information.