BMA Concise Guide to Medicine & Drugs


Brand names Action Cold Sore Cream, Boots Avert, Cymex Ultra, Lypsyl Aciclovir 5%, Soothelip, Virasorb, Zovirax

Used in the following combined preparations None


Drug group Antiviral drug

Overdose danger rating Low

Dependence rating Low

Prescription needed No (cold sore cream); Yes (other preparations)

Available as generic Yes


Aciclovir is an antiviral drug used in the treatment of herpes infections, which can cause cold sores and genital herpes. It is available as tablets, a liquid, a cream, eye ointment, and injection. The cream is commonly used to treat cold sores, and can speed up the healing of the lesions, provided it is started as soon as symptoms occur and as the lesions appear. The tablets and injection are used to treat severe herpes infections, shingles, chickenpox, and genital herpes. The tablets can also be used to prevent the development of herpes infection in people who have reduced immunity. Herpes infection affecting the eye can be treated with an eye ointment.


Follow instructions on the label. Call your doctor if symptoms worsen.

How taken/used Tablets, liquid, injection, cream, eye ointment.

Frequency and timing of doses 2–5 x daily. Start as soon as possible.

Adult dosage range Tablets, liquid 1–4g daily (treatment); 800mg–1.6g daily (prevention). Cream, eye ointment 5 x daily.

Onset of effect Within 24 hours.

Duration of action Up to 8 hours.

Diet advice It is necessary to drink plenty of water when taking high doses by mouth or injection.

Storage Keep in original container at room temperature out of the reach of children. Protect from light.

Missed dose Tablets/liquid Take as soon as you remember. Cream, eye ointment Do not apply the missed dose. Apply your next dose as usual.

Stopping the drug Complete the full course as directed.

Exceeding the dose An occasional unintentional extra dose is unlikely to be a cause for concern. But if you notice any unusual symptoms, or if a large overdose has been taken, notify your doctor.


Serious adverse effects are rare. Topical applications commonly cause burning, stinging, and itching at the site of application, or, rarely, a rash; if a rash occurs, stop taking the drug and consult your doctor. Taken by mouth, aciclovir may occasionally cause nausea, vomiting, dizziness, confusion, hallucinations, or a rash. Discuss with your doctor if nausea and/or vomiting are severe or if any of the other effects occur. Administered by injection, aciclovir may rarely cause inflammation at the injection site, confusion, or hallucinations. If any of these effects occur, talk to your doctor.


General note Any drug that affects the kidneys increases the risk of side effects with aciclovir.

Probenecid and cimetidine These drugs may increase the level of aciclovir in the blood.

Mycophenolate mofetil Aciclovir may increase the levels of this drug in the blood and vice.


Be sure to consult your doctor or pharmacist before taking this drug if:

· You have a long-term kidney problem.

· You have reduced immunity.

· You are taking other medicines.

Pregnancy Topical preparations carry no known risk. Oral and injectable forms may be prescribed if the benefits outweigh the risks. Discuss with your doctor.

Breast-feeding No evidence of risk with topical forms. The drug passes into the breast milk following injection or oral administration. Discuss with your doctor.

Infants and children Reduced dose necessary in young children.

Over 60 Reduced dose may be necessary.

Driving and hazardous work No known problems.

Alcohol No known problems.


Aciclovir is usually given as single courses of treatment and is not given long term, except for people with reduced immunity.