What it is used for
- Cold sores (herpes labialis)
- Genital herpes
- Shingles (herpes zoster)
- Prevention of recurrent herpes outbreaks
- Reducing transmission of genital herpes
How it works
Valaciclovir is converted in the body into aciclovir, which blocks the enzyme herpes viruses use to copy their DNA. Because it is absorbed more efficiently, it can be taken less often than aciclovir. It controls the virus but does not clear it from the body.
How it is taken
Available as tablets taken by mouth. It works best when started as soon as symptoms appear. Take it exactly as your doctor, pharmacist, or the label directs, complete the full course, and keep well hydrated. Do not stop early just because symptoms improve.
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
- Stomach pain
- Dizziness
- Tiredness
- Diarrhoea
Serious effects — get help
- Confusion, hallucinations, or unusual drowsiness
- Signs of kidney problems (little or no urine, swelling, back pain)
- Severe allergic reaction
- Unusual bruising, bleeding, or signs of a blood disorder (especially in people with weakened immune systems)
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 and cimetidine (can raise drug levels)
- Some immunosuppressants such as mycophenolate
- Inform your clinician of all medicines you take
Who should take care
- Tell your doctor about kidney problems, as the dose may need adjusting
- Use with caution in people with weakened immune systems
- Stay well hydrated
- Use in pregnancy or breastfeeding only on clinical advice
- Older adults may need closer monitoring