entecavir

Action and Spectrum

Actions and Spectrum:

Action:

• entecavir is a nucleoside analogue reverse transcriptase inhibitor (NRTI). It works by inhibiting the reverse transcriptase enzyme, which is essential for the replication of the hepatitis B virus.
• By incorporating itself into the growing viral DNA chain, entecavir blocks the reverse transcription process, preventing the virus from reproducing and reducing the viral load in the body.
• entecavir is more selective for viral polymerases (enzymes involved in viral replication) than for human polymerases, minimizing its impact on normal cellular functions.

Spectrum:

• entecavir is specifically indicated for the treatment of chronic hepatitis B in adults and children 2 years of age and older with evidence of active viral replication and either persistent elevations in serum alanine aminotransferase (ALT) levels or evidence of active liver inflammation.
• It is effective against hepatitis B virus (HBV), including wild-type HBV and strains with resistance mutations to other nucleoside/nucleotide analogues.
• entecavir has a high genetic barrier to resistance, meaning that it is less prone to developing drug-resistant mutations compared to some other antiviral medications used in the treatment of hepatitis B.

Drug Interaction

Adverse Reaction

Frequency defined

1-10%

Headache (2-4%)

Nausea

Dizziness

Fatigue (1-3%)

<1%

Dyspepsia

Diarrhea

Vomiting

Insomnia

Somnolence

Post marketing Reports

Increased transaminases

Lactic acidosis

Black Box Warning

Black Box Warning:

None

Contraindication / Caution

Contraindications:

• Hypersensitivity: entecavir should not be used in individuals with a known hypersensitivity or allergic reaction to the drug or any of its components. Allergic reactions can range from mild skin rashes to severe reactions like anaphylaxis, a potentially life-threatening condition.

Cautions:

• HIV Coinfection: entecavir is primarily indicated for the treatment of chronic HBV infection and may not be suitable for individuals coinfected with HIV and HBV. If a patient has both HBV and HIV infection, it is important to consider the potential impact on the patient’s HIV treatment regimen and choose an appropriate antiviral therapy that addresses both infections.
• Renal Impairment: entecavir is primarily eliminated from the body through the kidneys. Therefore, caution is advised when using entecavir in individuals with impaired renal function. Dose adjustments may be necessary based on the patient’s estimated creatinine clearance.
• Lactic Acidosis and Hepatomegaly with Steatosis: Rare cases of lactic acidosis (a buildup of lactic acid in the blood) and hepatomegaly with steatosis (enlarged liver with fat accumulation) have been reported in patients receiving entecavir, particularly in those with underlying liver disease or risk factors. Monitoring liver function and overall clinical status is important during treatment.
• Resistance and Viral Flare: During the treatment of chronic HBV infection with entecavir, the emergence of resistant viral strains is possible. Regular monitoring of viral load and liver function is necessary to assess treatment response and detect any potential resistance.

Pregnancy / Lactation

Pregnancy consideration: N/A

Lactation: N/A

Pregnancy category:

• Category A: well-controlled and Satisfactory studies show no risk to the fetus in the first or later trimester.
• Category B: there was no evidence of risk to the fetus in animal studies, and there were not enough studies on pregnant women.
• Category C: there was evidence of risk of adverse effects in animal reproduction studies, and no adequate evidence in human studies must take care of potential risks in pregnant women.
• Category D: adequate data with sufficient evidence of human fetal risk from various platforms, but despite the potential risk, and used only in emergency cases for potential benefits.
• Category X: Drugs listed in this category outweigh the risks over benefits. Hence these categories of drugs need to be avoided by pregnant women.

Category N: There is no data available for the drug under this category.

Pharmacology

Pharmacology:

entecavir is a medication used in the treatment of chronic hepatitis B virus (HBV) infection. Here is an overview of the pharmacology of entecavir:

Pharmacodynamics:

entecavir is a potent inhibitor of HBV DNA polymerase, an enzyme necessary for the replication of the hepatitis B virus. It selectively inhibits viral replication by competing with the natural substrate, deoxyguanosine triphosphate (dGTP), and incorporating itself into the growing viral DNA chain. This results in chain termination and prevents the elongation of viral DNA, thereby reducing viral replication.

Pharmacokinetics:

Absorption

entecavir is well absorbed after oral administration. Food does not significantly affect its absorption, so it can be taken with or without food.

Distribution

entecavir is distributed widely throughout the body, including the liver, where the hepatitis B virus primarily replicates. It has a high binding affinity to plasma proteins (approximately 13%) but does not extensively bind to red blood cells.

Metabolism

entecavir undergoes minimal metabolism in the liver. The majority of the drug is excreted unchanged in the urine.

Elimination and excretion

entecavir is primarily eliminated by renal excretion. Approximately 60-70% of an administered dose is excreted unchanged in the urine, with the remainder being eliminated as metabolites.

Adminstartion

Administration:

entecavir is an antiviral medication primarily used in the treatment of chronic hepatitis B virus (HBV) infection. It is available in oral tablet form.

The recommended dosage of entecavir may vary depending on the patient’s age, liver function, and other factors. It is important to follow the prescribed dosage as directed by the healthcare professional.

entecavir is taken orally by mouth. The tablets should be swallowed whole with water and can be taken with or without food.

Patient Information Leaflet

Patient information leaflet

Generic Name: entecavir

Why do we use entecavir?

entecavir is used for the treatment of chronic hepatitis B virus (HBV) infection. Here are the reasons why entecavir is commonly prescribed:

• Antiviral Activity: entecavir is a potent inhibitor of HBV replication. It works by blocking the action of HBV’s reverse transcriptase enzyme, which is necessary for the virus to replicate and produce new viral DNA. By suppressing viral replication, entecavir helps to reduce the viral load in the body.
• Effective Suppression of HBV: entecavir has demonstrated high efficacy in reducing HBV DNA levels in both treatment-naive patients (those starting antiviral therapy for the first time) and patients with prior treatment experience. It has been shown to achieve significant viral suppression, leading to improved liver function and a decrease in liver inflammation.
• Low Risk of Resistance: entecavir has a high genetic barrier to resistance, meaning that it is less prone to the development of drug-resistant HBV strains compared to some other antiviral medications.