HBV Treatment Drugs
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Direct answer
Chronic hepatitis B is suppressed, not eradicated: either pegylated interferon alfa-2a (a finite 48-week, parenteral course) or long-term oral nucleos(t)ide analogues — tenofovir disoproxil fumarate 300 mg daily, tenofovir alafenamide 25 mg daily, or entecavir 0.5 mg daily. Treatment is indicated when HBV DNA is elevated with active hepatitis (ALT roughly double the upper limit for months) or significant fibrosis, and in any cirrhosis with detectable DNA. The drugs block viral replication, normalise ALT, allow HBeAg seroconversion in a subset, and cut hepatocellular carcinoma risk — but therapy for most patients means years, with monitoring, not a finish line.
What you must remember
- Tenofovir disoproxil fumarate (TDF) 300 mg OD: potent, essentially no resistance at 5 years; the price is renal tubular dysfunction (Fanconi-like picture) and bone density loss — monitor creatinine and phosphate.
- Tenofovir alafenamide (TAF) 25 mg OD: the same target with far lower plasma tenofovir, hence better renal and bone profile — preferred where kidney or bone risk exists.
- Entecavir 0.5 mg OD (1 mg in lamivudine resistance): high barrier to resistance; absorbed poorly with food, so it goes on an empty stomach — a detail examiners love.
- Lamivudine 150 mg OD: cheap and on the NLEM, but resistance accrues at roughly 20% per year (rtM204V/I) — monotherapy is obsolete except where cost truly binds.
- Peg-IFN alfa-2a 180 μg weekly × 48 weeks: finite course with the best chance of HBeAg loss in HBeAg-positive disease; flu-like illness, cytopenias, depression; never in decompensated cirrhosis or pregnancy.
- Pregnancy: TDF when HBV DNA exceeds 200,000 IU/mL in the third trimester, alongside neonatal vaccine plus hepatitis B immunoglobulin, to block vertical transmission.
- HIV coinfection: never give lamivudine or entecavir alone — monotherapy selects resistant HIV mutants; use a tenofovir-based antiretroviral regimen.
- Monitoring: ALT and HBV DNA every 3–6 months; 6-monthly liver ultrasound ± AFP for HCC surveillance in cirrhosis and high-risk carriers.
How to decide whom to treat
The natural history sorts patients into phases, and only some get drugs. The immune-tolerant young adult — HBV DNA in the millions, normal ALT, HBeAg positive — is observed, because drugs there buy resistance and little else; the immune system is not yet fighting, so there is nothing to amplify. The immune-clearance phase is the treatment window: DNA above roughly 20,000 IU/mL with sustained ALT elevation or significant fibrosis on transient elastography or biopsy. Compensated cirrhosis with any detectable DNA gets oral therapy regardless of ALT, and decompensated cirrhosis gets oral agents urgently (never interferon) with transplant referral. HBeAg-positive patients who seroconvert to anti-HBe on therapy may consolidate for a year and stop; HBeAg-negative disease usually needs therapy indefinitely because relapse follows withdrawal. Walk this phase-by-phase ladder in a viva and the examiner stops asking questions.
High-yield viva angles
Three traps recur. First, "why not treat the immune-tolerant patient?" — because suppression without an immune attack yields no durable endpoint and burns resistance potential. Second, entecavir dosing: with food its absorption falls substantially, so "empty stomach, two hours after dinner" is a counselling fact, not trivia. Third, the antiviral safety ledger: TDF's Fanconi syndrome and osteomalacia against TAF's cleaner kidney and bone profile; interferon's absolute exclusions (decompensation, pregnancy, autoimmune disease). A fourth favourite asks why lamivudine remains on the NLEM at all — cost and access, with the explicit understanding that its 20% yearly resistance is the accepted trade in resource-limited settings. Frame every answer around "potency, resistance barrier, safety, duration" and the class organises itself.
Frequently asked questions
Which HBV drugs have the lowest resistance rates?
Tenofovir (TDF and TAF) and entecavir — essentially negligible resistance over five years, unlike lamivudine's roughly 20% per year.
Why is peg-interferon contraindicated in decompensated cirrhosis?
It is immunostimulatory and cytopenic, risking precipitous hepatic decompensation and infection in a failing liver.
What is the pregnancy rule for chronic hepatitis B?
Tenofovir in the third trimester when HBV DNA exceeds 200,000 IU/mL, plus neonatal vaccine and HBIG, prevents vertical transmission.
Why must entecavir be taken on an empty stomach?
Food substantially reduces entecavir absorption, so it is dosed away from meals to reach effective levels.
What is the main endpoint beyond viral suppression?
HBeAg seroconversion to anti-HBe allows finite therapy in HBeAg-positive disease; HBsAg loss is the rare, idealised endpoint.