What it is used for
- Cold sores (herpes labialis)
- Genital herpes
- Shingles (herpes zoster)
- Chickenpox (varicella)
- Herpes simplex eye and skin infections
How it works
Aciclovir is taken up by virus-infected cells and converted into an active form that blocks the enzyme the herpes virus uses to copy its DNA. This stops the virus from multiplying, helping the body bring the infection under control. It does not cure or remove the virus from the body permanently.
How it is taken
Comes as tablets, dispersible tablets, oral liquid/suspension, cream for the lips or skin, eye ointment, and an injectable form used in hospital. Oral and topical forms work best when started as early as possible after symptoms begin. Take or apply it exactly as your doctor, pharmacist, or the product label directs, and complete the full course even if you feel better. Drinking plenty of fluids while taking it is generally advised.
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
- Nausea or vomiting
- Diarrhoea
- Headache
- Dizziness
- Tiredness
- Mild skin reactions with the cream
Serious effects — get help
- Signs of kidney problems such as passing little or no urine, swelling, or back pain
- Confusion, hallucinations, agitation, or unusual drowsiness
- Severe allergic reaction (rash, swelling of face or throat, difficulty breathing)
- 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
- Other medicines that can affect the kidneys (such as some painkillers and certain antibiotics)
- Probenecid (can raise aciclovir levels)
- Mycophenolate and some immunosuppressants
- Tell your clinician about all medicines, including over-the-counter and herbal products
Who should take care
- Tell your doctor if you have kidney problems, as the dose may need adjusting
- Keep well hydrated while taking it
- Use in pregnancy or breastfeeding only on a clinician's advice
- Older adults may be more sensitive to side effects
- Tell your doctor about any allergy to aciclovir or valaciclovir