What it is used for
- Shingles (herpes zoster)
- Genital herpes outbreaks
- Cold sores
- Prevention of recurrent genital herpes
How it works
Famciclovir is converted in the body into penciclovir, which blocks the enzyme herpes viruses use to copy their DNA, stopping the virus from multiplying. It eases symptoms and speeds healing of outbreaks but does not remove the virus from the body.
How it is taken
Available as tablets taken by mouth, with or without food. It works best when started as soon as symptoms begin, such as the first tingling or pain of an outbreak. Take it exactly as your doctor, pharmacist, or label directs and complete the full course.
No doses here on purpose. The right strength and schedule depend on you — only a doctor or pharmacist should set them. Always follow your prescription and the label.
Common side effects
- Headache
- Nausea
- Diarrhoea
- Dizziness
- Tiredness
Serious effects — get help
- Confusion, hallucinations, or unusual drowsiness, especially in older adults or those with kidney problems
- Signs of a severe skin reaction
- Severe allergic reaction
- Unusual bruising or bleeding
If a reaction is severe — for example trouble breathing, swelling of the face or throat, or collapse — go to the nearest emergency room now or call your local emergency number. Do not wait for an online consultation.
Interactions to watch
- Medicines that affect the kidneys
- Probenecid (can raise drug levels)
- Tell your clinician about all your medicines
Who should take care
- Tell your doctor about kidney problems, as the dose may need adjusting
- Older adults may be more prone to confusion or drowsiness
- Use in pregnancy or breastfeeding only on clinical advice
- Mention any previous reaction to aciclovir, valaciclovir, or famciclovir