Vemlidy Tenofovir Alafenamide Fumarate Tablets

1. Indications and Usage
Treatment of Chronic Hepatitis B Virus (HBV) Infection:
Indicated for the treatment of chronic hepatitis B virus (HBV) infection in adults and adolescents (aged 12 years and older, weighing at least 35 kg).
2. Dosage and Administration
Recommended Dosage:
Adults and Adolescents (≥12 years and ≥35 kg): 25 mg tablet, orally, once daily with food.
Adults with Severe Renal Impairment (CrCl < 30 mL/min) or End-Stage Renal Disease (ESRD):Dosage adjustment is not required.
Administration Instructions:
Must be taken with food to ensure adequate bioavailability.
Do not administer to patients with unknown or undiagnosed liver disease without confirming HBV status.
Missed Dose:
If a dose is missed and it is less than 18 hours since the usual time of dosing, take the dose as soon as possible with food and resume the normal schedule.
If more than 18 hours have passed, skip the missed dose and resume the normal schedule.
3. Mechanism of Action
Nucleotide Analog Reverse Transcriptase Inhibitor (NRTI):
Tenofovir alafenamide (TAF) is a nucleotide analog reverse transcriptase inhibitor.
Pathway:
TAF is a prodrug of tenofovir. It is more stable in plasma than tenofovir disoproxil fumarate (TDF) and is efficiently taken up by hepatocytes (liver cells).
Physiological Effect:
Inside the cell, TAF is hydrolyzed to tenofovir, which is then phosphorylated to the active metabolite, tenofovir-diphosphate.
Tenofovir-diphosphate inhibits HBV polymerase (reverse transcriptase) by competing with the natural substrate (deoxyadenosine 5′-triphosphate) and incorporating into viral DNA, resulting in DNA chain termination.
4. Safety and Warnings
Hepatitis B Exacerbations:
Severe acute exacerbations of hepatitis B have been reported in patients who have discontinued anti-hepatitis B therapy, including TAF. Hepatic function should be monitored closely for at least several months after stopping treatment.
Renal Impairment:
Although TAF has a lower risk of renal toxicity compared to TDF, renal impairment (including acute renal failure and Fanconi syndrome) has been reported. Monitor creatinine clearance (CrCl) and urine glucose in patients with renal risk factors.
Bone Toxicity:
TAF has a lower risk of bone toxicity compared to TDF, but decreases in bone mineral density (BMD) have been observed.
Immune Reconstitution Syndrome:
In patients coinfected with HIV-1 and HBV, the possibility of immune reconstitution syndrome should be considered when anti-HBV therapy is initiated.
5. Adverse Reactions
Most Common:
Headache (12%), fatigue (6%), and nausea (6%).
Other:
Diarrhea, abdominal pain, dyspepsia, rash, and pruritus.
6. Drug Interactions
P-glycoprotein (P-gp) Inducers:
Drugs that induce P-gp (e.g., rifampin, carbamazepine, phenytoin) may significantly decrease plasma concentrations of TAF, leading to loss of therapeutic effect. Concomitant use is not recommended.
Drugs that Increase Renal Proximal Tubule Transport:
Concomitant use with drugs that compete for renal transport (e.g., cobicistat, ritonavir, lopinavir/ritonavir) may increase TAF plasma concentrations and the risk of adverse reactions.
Antacids:
Concomitant use with antacids containing aluminum, magnesium, or calcium may reduce TAF absorption.
7. Pharmaceutical Information
Chemical Name:
Propan-2-yl (S)-((S)-(((2R)-1-(6-amino-9H-purin-9-yl)propan-2-yl)oxy)methyl)(phenoxy)phosphoryl)amino)butanoate fumarate.
Molecular Formula:
C21H29N6O5P·C4H4O4.
Storage:
Store at 25°C (77°F); excursions permitted to 15-30°C (59-86°F). Protect from moisture.