Antavir Tablet

Antavir is a guanosine nucleoside analogue with potent and selective activity against HBV polymerase. For pharmacological action it is phosphorylated to the active triphosphate (TP) form. Antavir triphosphate functionally inhibits all 3 activities of the viral polymerase-

  • Priming of the HBV polymerase,
  • Reverse transcription of the negative strand from the pregenomic messenger RNA
  • Synthesis of the positive strand HBV DNA.


Antavir is used for the treatment of chronic hepatitis B virus infection in adults with compensated liver disease, evidence of viral replication and histologically documented active liver inflammation or fibrosis. It is also effective in decompensated cirrhosis.

Antavir is also used to associated treatment for these conditions: Hepatitis B Chronic Infection

Trade Name Antavir
Generic Entecavir
Other Names Entecavir, Entecavirum
Weight 0.5mg
Type Tablet
Formula C12H15N5O3
Weight Average: 277.2792
Monoisotopic: 277.117489371
Protein binding

Binding of entecavir to human serum proteins in vitro is approximately 13%.

Therapeutic Class Hepatic viral infections (Hepatitis B)
Manufacturer Opsonin Pharma Ltd
Available Country Bangladesh
Last Updated: June 23, 2021 at 11:20 am


Antavir dosage

Administration of Antavir with food decreases absorption and so it should be taken in an empty stomach (at least 2 hours before or 2 hours after meal). 

Adult over 16 years, not previously treated with nucleoside analogues: 0.5 mg once daily.

Adult over 16 years with lamivudine or telbivudine resistant chronic hepatitis B: 1 mg once daily.

Side Effects

The most common side effects are headache, fatigue, dizziness and nausea.


Monitor liver function tests every 3 months, and viral and serological markers for hepatitis B every 3-6 months. Discontinue if deterioration in liver function, hepatic steatosis, progressive hepatomegaly or unexplained lactic acidosis. Recurrent hepatitis may occur on discontinuation.


Since Antavir is predominantly eliminated by the kidney, coadministration with drugs that reduce renal function or compete for active tubular secretion may increase serum concentrations of either drug.

Food Interaction

  • Take on an empty stomach. Take 2 hours before or 2 hours after a meal.

Half Life

After reaching peak concentration, entecavir plasma concentrations decreased in a bi-exponential manner with a terminal elimination half-life of approximately 128-149 hours. The phosphorylated metabolite has a half-life of 15 hours.


  • renal cl=383.2 +/- 101.8 mL/min [Unimpaired renal function]
  • renal cl=197.9 +/- 78.1 mL/min [Mild impaired renal function]
  • renal cl=135.6 +/- 31.6 mL/min [Moderate impaired renal function]
  • renal cl=40.3 +/- 10.1 mL/min [severe impaired renal function]
  • apparent oral cl=588.1 +/- 153.7 mL/min [Unimpaired renal function]
  • apparent oral cl=309.2 +/- 62.6 mL/min [Mild impaired renal function]
  • apparent oral cl=226.3 +/- 60.1 mL/min [Moderate impaired renal function]
  • apparent oral cl=100.6 +/- 29.1 mL/min [severe impaired renal function]
  • apparent oral cl=50.6 +/- 16.5 mL/min [severe impaired renal function amnaged with Hemodialysis]
  • apparent oral cl=35.7 +/- 19.6 mL/min [severe impaired renal function amnaged with CAPD]

Pregnancy & Breastfeeding use

Use in pregnancy: There are no adequate and well-controlled studies in pregnant women. Antavir should be used during pregnancy only if the potential benefit justifies the potential risk to the fetus.

Use in lactation: It is not known whether Antavir is excreted in human milk. Mothers should be instructed not to breast-feed if they are taking Antavir.


Antavir is contraindicated in patients with previously demonstrated hypersensitivity to Antavir or any component of the product.

Special Warning

Use in pediatric patient: Safety and effectiveness of Antavir in pediatric patients below the age of 16 years have not been established.

Use in geriatric patient: Antavir is significantly excreted by the kidney, and the risk of toxic reactions to this drug may be greater in patients with impaired renal function. Because elderly patients are more likely to have decreased renal function, care should be taken in dose selection, and it may be useful to monitor renal function.

Dose adjustment in renal impairment: Dose adjustment is recommended for patients with CrCl <50 ml/min including patients on hemodialysis or continuous ambulatory peritoneal dialysis (CAPD) as shown in the following table.

CrCl ≥50 ml/min: 0.5 mg every 24 hours

CrCl 30 to <50 ml/min: 0.5 mg every 48 hours

CrCl 10 to <30 ml/min: 0.5 mg every 72 hours

CrCl <10 ml/min or  Hemodialysis or CAPD: 0.5 mg every 7 days

Acute Overdose

There is no experience of Antavir overdosage reported in patients. Healthy subjects who received up to 20 mg daily for up to 14 days and single doses up to 40 mg had no unexpected adverse events. If overdosage occurs, the patient must be monitored for evidence of toxicity and standard supportive treatment as necessary.

Storage Condition

Store at temperatures not above 30°C.

Antavir contains Entecavir see full prescribing information from innovator Monograph