References UK clinical guidance from the NHS, the British HIV Association (BHIVA), and the British Association for Sexual Health and HIV (BASHH). Last updated: April 2026.
Famvir is the brand name for famciclovir, an antiviral medication used to treat herpes simplex (cold sores and genital herpes) and herpes zoster (shingles). It’s a third-generation antiviral similar to aciclovir and valaciclovir, offering convenient dosing and good effectiveness. Famvir is prescription-only in the UK.
Here’s what you need to know.
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What Famvir Treats
| Condition | Typical Use |
|---|---|
| Genital herpes (HSV) | Episodic or suppressive treatment |
| Cold sores (HSV-1) | Episodic treatment |
| Shingles (varicella zoster) | Treatment of acute shingles |
| Post-herpetic neuralgia prevention | Reduces nerve pain after shingles |
How It Works
Famciclovir is a prodrug — once in the body, it’s converted to penciclovir, which blocks herpes viruses from replicating. It’s taken as tablets (not a cream) and works systemically.
Dosing
- Episodic genital herpes — 125-250mg twice daily for 5 days, or higher dose short-course regimens
- Suppressive therapy — 250mg twice daily
- Cold sores — 1500mg single dose or short course
- Shingles — 750mg three times daily or 500mg three times daily for 7 days
How to Take It
- With or without food
- Take the full course as prescribed
- Start treatment as soon as symptoms begin — works best early
Side Effects
Generally well tolerated. Possible side effects include:
- Headache
- Nausea
- Dizziness
- Fatigue
- Rash (rare)
Serious side effects are uncommon.
Famvir vs Aciclovir vs Valaciclovir
- Aciclovir — well-established, cheaper, sometimes taken more often
- Valaciclovir — prodrug of aciclovir, better oral absorption, less frequent dosing
- Famvir (famciclovir) — prodrug of penciclovir, similar to valaciclovir
All three work similarly well. Choice often depends on local prescribing habits and cost.
When to Use Famvir
- For people who prefer shorter courses
- For those who don’t tolerate aciclovir
- For suppressive therapy when convenient dosing matters
Precautions
- Not recommended for people with severe kidney problems without dose adjustment
- Discuss with your doctor if pregnant or breastfeeding
- Tell your doctor about other medications
Read more: What is herpes? | Do I have herpes? | HSV-1 vs HSV-2
Frequently Asked Questions
Is Famvir better than aciclovir?
Not better — comparable effectiveness. Choice depends on dosing preferences and tolerance.
Can I buy it over the counter?
No — prescription only in the UK.
How quickly does it work?
Best if started early — within 24-48 hours of symptoms appearing.
Related reading
- Can You Get Herpes From a Toilet Seat?
- Can You Get Herpes From Kissing?
- Comprehensive Test: Chlamydia, Gonorrhoea and Herpes
- Cold Sores vs Syphilis Sores: How to Tell the Difference
- Genital Warts vs Herpes: What's the Difference?
Sources
- NHS — Sexual health conditions
- BASHH — UK clinical guidelines for STI management
- British HIV Association (BHIVA) — HIV treatment guidelines
- Terrence Higgins Trust — sexual health information
- UK Health Security Agency — STI surveillance data
Steve Page is a recognised expert on Sexually Transmitted Diseases (STDs) and STD treatments, having published numerous articles in peer-reviewed journals and presented his research at conferences around the world. He has an in-depth understanding of the latest medical research on STDs, and is an advocate for the development of new treatments and protocols to improve the health of those affected. In addition to his research, he has dedicated his career to understanding the causes and symptoms of STDs, as well as how to best treat those impacted.
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