Entecavir

Uses

Entecavir 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.

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

How Entecavir works

By competing with the natural substrate deoxyguanosine triphosphate, entecavir functionally inhibits all three activities of the HBV polymerase (reverse transcriptase, rt): (1) base priming, (2) reverse transcription of the negative strand from the pregenomic messenger RNA, and (3) synthesis of the positive strand of HBV DNA. Upon activation by kinases, the drug can be incorporated into the DNA which has the ultimate effect of inhibiting the HBV polymerase activity.

Dosage

Entecavir dosage

Administration of Entecavir 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.

Toxicity

Healthy subjects who received single entecavir doses up to 40 mg or multiple doses up to 20 mg/day for up to 14 days had no increase in or unexpected adverse events. If overdose occurs, the patient must be monitored for evidence of toxicity, and standard supportive treatment applied as necessary.

Precaution

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.

Interaction

Since Entecavir 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.

[Moderate] ADJUST DOSING INTERVAL: Food delays the oral absorption and reduces the oral bioavailability of entecavir.

According to the product labeling, administration of entecavir 0.5 mg with a standard high-fat meal or a light meal resulted in a delay in absorption by 0.25 to 0.75 hours, a decrease in the peak plasma concentration (Cmax) by 44% to 46%, and a decrease in the area under the plasma concentration-time curve (AUC) by 18% to 20% compared to administration in the fasting state.

MANAGEMENT: To ensure maximal oral absorption, entecavir should be administered on an empty stomach at least 2 hours after a meal and 2 hours before the next meal.

Entecavir Drug Interaction

Unknown: aspirin, aspirin, aspirin, aspirin, ginkgo, ginkgo, metoprolol, metoprolol, acetaminophen, acetaminophen, omeprazole, omeprazole, levothyroxine, levothyroxine, valproic acid, valproic acid, ascorbic acid, ascorbic acid, cholecalciferol, cholecalciferol

Entecavir Disease Interaction

Major: hepatotoxicityModerate: hemodialysis, renal dysfunction

Elimination Route

Absorption Following oral administration in healthy subjects, entecavir peak plasma concentrations occurred between 0.5 and 1.5 hours. In healthy subjects, the bioavailability of the tablet is 100% relative to the oral solution.

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.

Clearance

• 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. Entecavir 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 Entecavir is excreted in human milk. Mothers should be instructed not to breast-feed if they are taking Entecavir.

Contraindication

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

Special Warning

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

Use in geriatric patient: Entecavir 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 Entecavir 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.

Innovators Monograph

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