Generic Name: Entecavir 0.5 mg & 1 mg
Therapeutic Class: Nucleoside Reverse Transcriptase Inhibitors (Antivirals)
Indications
Entecavir is indicated for the treatment of **Chronic Hepatitis B Virus (HBV) infection** in adults and pediatric patients (2 years of age and older) with evidence of active viral replication. It is used in patients with:
- Compensated liver disease with evidence of persistent elevations in serum aminotransferases (ALT or AST) or histologically active disease.
- Decompensated liver disease (specifically in adults).
- Both HBeAg-positive and HBeAg-negative chronic HBV infection.
- Lamivudine-refractory or resistant Hepatitis B.
Presentation
Tablet: Available as film-coated tablets containing Entecavir INN 0.5 mg or 1 mg.
Description
Entecavir is a guanosine nucleoside analogue with potent and selective activity against HBV polymerase. It is efficiently phosphorylated to the active triphosphate (TP) form, which has an intracellular half-life of 15 hours. Entecavir triphosphate inhibits HBV polymerase by competing with the natural substrate deoxyguanosine triphosphate, effectively blocking all three functional activities of the viral polymerase: (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.
Dosage & Administration
Entecavir should be taken on an **empty stomach** (at least 2 hours after a meal and at least 2 hours before the next meal).
- Compensated Liver Disease (Nucleoside-naive): 0.5 mg once daily.
- Compensated Liver Disease (Lamivudine-refractory): 1 mg once daily.
- Decompensated Liver Disease: 1 mg once daily.
- Renal Impairment: Dosage adjustment is required if Creatinine Clearance is < 50 mL/min.
- ClCr 30-49: 0.25 mg once daily (or 0.5 mg every 48 hours).
- ClCr 10-29: 0.15 mg once daily (or 0.5 mg every 72 hours).
- ClCr < 10 (Hemodialysis): 0.05 mg once daily (or 0.5 mg every 7 days).
Side Effects
The most common side effects include headache, fatigue, dizziness, and nausea. In patients with decompensated liver disease, more serious side effects like peripheral edema, ascites, and pyrexia may occur. Rare but serious side effects include **Lactic Acidosis** and severe hepatomegaly with steatosis. Severe acute exacerbations of hepatitis B have been reported in patients who have discontinued anti-hepatitis B therapy.
Pregnancy & Lactation
Pregnancy: Pregnancy Category C. 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.
Lactation: It is not known whether Entecavir is excreted in human milk. Mothers should be instructed not to breastfeed if they are taking Entecavir.
Lactation: It is not known whether Entecavir is excreted in human milk. Mothers should be instructed not to breastfeed if they are taking Entecavir.
Precautions & Interactions
Precautions: Renal function should be monitored before and during therapy. Patients co-infected with HIV/HBV who are not receiving HAART should not use Entecavir as it may lead to the development of HIV resistance.
Interactions: Since Entecavir is primarily eliminated by the kidneys, co-administration with drugs that reduce renal function or compete for active tubular secretion may increase serum concentrations of either drug.
Interactions: Since Entecavir is primarily eliminated by the kidneys, co-administration with drugs that reduce renal function or compete for active tubular secretion may increase serum concentrations of either drug.
Overdose
There is limited experience with Entecavir overdose reported in patients. If overdose occurs, the patient must be monitored for evidence of toxicity, and standard supportive treatment should be applied. A 4-hour hemodialysis session can remove approximately 13% of the Entecavir dose.
Storage
Store in a cool and dry place, below 30°C. Protect from light and moisture. Keep the container tightly closed and out of reach of children.
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