Istergan (Entecavir)

• Entecavir is an antiviral medication used primarily in the management of hepatitis B virus (HBV) infection.
• Chronic hepatitis B infection: reduces HBV DNA levels, improves liver enzyme profiles, and helps prevent progression to cirrhosis or liver cancer.
• Compensated liver disease due to hepatitis B: maintains hepatic function and reduces the risk of decompensation.
• HBV carriers (asymptomatic): lowers viral replication to decrease transmission risk and long‑term liver damage.

• Entecavir is a nucleoside analogue that is phosphorylated intracellularly to its active triphosphate form. The active metabolite competitively inhibits the hepatitis B virus DNA polymerase (reverse transcriptase), blocking all three activities of the enzyme—priming, reverse transcription of pregenomic RNA, and synthesis of the negative‑strand DNA—thereby preventing viral replication. By halting the formation of new viral particles, entecavir reduces the amount of circulating virus and allows the immune system to control infection more effectively.

Entecavir may be associated with adverse reactions that vary in frequency and severity.

Common Side Effects

• Fatigue: mild to moderate tiredness reported by some patients.
• Headache: occasional tension‑type headaches.
• Nausea: transient stomach upset, often resolves with continued therapy.
• Dizziness: occasional light‑headed sensation.

Serious or Rare Side Effects

• Lactic acidosis: rare metabolic complication requiring immediate medical attention.
• Severe allergic reaction: includes rash, swelling, or anaphylaxis.
• Hepatic decompensation: worsening liver function in patients with advanced disease.

• When prescribing entecavir, clinicians should consider several precautionary measures to ensure safe use.
• Liver function monitoring: Regularly assess ALT and AST levels to detect hepatic changes.
• Renal function assessment: Evaluate creatinine clearance before initiating therapy, especially in patients with impaired kidneys.
• History of lactic acidosis: Use with caution in individuals with prior metabolic disorders.
• Avoid concurrent nucleoside analogues: Combining with similar agents may increase toxicity risk.
• Store at ambient temperature: keep below 25°C in the original container, protect from moisture and light.

Entecavir may interact with other medicines, requiring attention to potential effects.

Major Interactions (Avoid)

• Co‑administration with other nucleos(t)ide analogues: may increase risk of mitochondrial toxicity.
• Combination with interferon therapy: can heighten adverse event profile.

Moderate Interactions (Monitor Closely)

• Use with nephrotoxic drugs: may necessitate dose adjustment of entecavir.
• Concurrent immunosuppressants: monitor for HBV reactivation.
• Oral contraceptives: potential reduction in contraceptive efficacy, advise additional protection.