A 32-year-old man with chronic hepatitis B infection (HBeAg-positive, HBV DNA >10^5 copies/mL) and compensated cirrhosis presents for antiviral therapy initiation. Which of the following is the preferred first-line nucleos(t)ide reverse transcriptase inhibitor for this patient?

Explanation

## First-Line Nucleos(t)ide Agents in Chronic Hepatitis B **Key Point:** Entecavir is the preferred first-line NRTI for chronic HBV infection, particularly in patients with cirrhosis or high viral loads, due to superior potency and a lower barrier to resistance. ### Comparison of Nucleos(t)ide Agents | Agent | Potency | Barrier to Resistance | Renal Toxicity | Bone Loss | First-Line Status | |-------|---------|----------------------|----------------|-----------|-------------------| | **Entecavir** | Very high | High | Minimal | Minimal | **Yes** | | Tenofovir DF | High | High | Moderate | Moderate | Alternative | | Lamivudine | Moderate | **Low** | None | None | No (resistance) | | Adefovir | Moderate | Moderate | **Yes** | **Yes** | No (toxicity) | **High-Yield:** Entecavir achieves HBV DNA suppression in >90% of treatment-naïve patients and is superior to lamivudine (which develops resistance in up to 70% by 5 years). The high barrier to resistance makes it ideal for cirrhotic patients where viral breakthrough could precipitate decompensation. ### Clinical Pearl **Warning:** Lamivudine monotherapy is now considered obsolete due to rapid emergence of YMDD mutants (tyrosine-methionine-aspartate-aspartate mutations), resulting in treatment failure and hepatic flare in up to 70% of patients by year 5. It should not be used as monotherapy in any patient with chronic HBV. ### Mechanism Entecavir is a guanosine nucleoside analogue that inhibits HBV reverse transcriptase with high selectivity and potency. Its high barrier to resistance (requires multiple mutations) makes it durable for long-term monotherapy, even in cirrhotic patients where treatment failure carries high risk. **Tip:** In the NEET PG exam, when you see "chronic HBV with cirrhosis" or "HBeAg-positive with high viral load," think **entecavir** as first-line. Tenofovir is an acceptable alternative but entecavir is preferred due to lower renal and bone toxicity. [cite:Harrison 21e Ch 297]