Available in cream or on prescription in tablet form, acyclovir acts directly on herpes, shingles and chickenpox viruses.
Cold sores, genital herpes, shingles… Acyclovir is one of the most used antiviral treatments. It was discovered in the 1970s from marine organisms, which explains its natural origin. Available as a cream or on prescription in tablet form, it acts directly on the viruses responsible for these infections. In what cases should it be used? Is it effective from the first symptoms? What are its side effects? Here’s what you need to know.
Definition: what is acyclovir?
Aciclovir is an antiviral medication used to treat certain infections caused by viruses in the herpes family. It mainly targets:
- herpes simplex virus (HSV-1, responsible for cold sores, and HSV-2, responsible for genital herpes)
- shingles and varicella virus (VZV)
It does not permanently cure the infection, but helps reduce the duration of symptoms, limit pain and avoid complications. It is found in several forms:
- cream or ointment (especially for cold sores)
- tablets or syrup
- eye ointment
- injection solution in hospital
Acyclovir works by blocking the multiplication of the virus in the body. Concretely, it prevents the virus from manufacturing its DNA, which stops its propagation in infected cells. It acts on several viruses of the same family: herpes, shingles, but also certain rarer viruses such as Epstein-Barr or cytomegalovirus in specific situations. It has the advantage of targeting only infected cells, without disturbing healthy cells, which explains why it is generally well tolerated. When taken orally, it is poorly absorbed (around 20%), which may require higher doses or administration in hospital in severe forms. After taking it, it acts quickly: its maximum concentration in the blood is reached in 1 to 2 hours. It spreads to several organs (such as the kidneys or the brain) before being eliminated mainly by the kidneys. Its duration of action is relatively short (around 3 hours), which explains the repeated doses during the day.
When to take acyclovir?
- Cold sore (herpes labialis)
- Genital herpes (first episode or recurrence)
- Shingles (to reduce duration and pain)
- Ocular herpes (on prescription)
It can also be prescribed for prevention in people who have frequent flare-ups (at least 6 per year) or in immunocompromised people. In some more serious cases, particularly in hospitals, it is used to treat severe infections:
herpetic meningoencephalitis, infections in infants or complications of shingles.
Treatment should be started as early as possible. Ideally within the first 48 hours following the appearance of symptoms, or even from the first tingling for a cold sore.
► As a cream (without prescription): apply 5 times a day to the affected area for approximately 5 days.
► In tablets (on prescription): several doses per day (often 2 to 5 depending on the case), the treatment lasts 5 to 10 days, sometimes longer for prevention.
Always wash your hands before and after application and avoid touching the lesions so as not to spread them. If you forget, do not double the dose. In the elderly or in case of kidney problems, the dose must be adjusted by the doctor. In the event of unusual symptoms (severe pain, affected eye, shingles, etc.), you should consult.
Acyclovir: with or without a prescription?
Without a prescription: cold sore creams
With prescription: tablets, syrup, ophthalmic ointment and injectable forms
Ophthalmic and oral forms require medical advice because they concern more sensitive infections.
Is acyclovir effective?
Yes, as long as you take it quickly.
It allows you to:
- shorten the duration of symptoms
- reduce pain
- limit contagion
- reduce the frequency of recurrences (as a preventive treatment)
On the other hand, it does not permanently eliminate the virus, which remains present in the body.
What are the side effects of acyclovir?
Acyclovir is generally well tolerated, but can cause:
- headache
- nausea, diarrhea, vomiting
- dizziness
- skin reactions (redness, tingling with the cream)
More rarely:
- kidney problems (in case of high doses or in fragile people)
- liver abnormalities
With local forms (creams), the effects are mainly irritation or a burning sensation.
What are the contraindications?
Aciclovir should not be used if you are allergic to the drug. Precautions are necessary:
- in case of renal failure
- in the elderly
- during breastfeeding: oral or injectable forms generally require medical advice, while creams are preferred if treatment is essential.
What is the price of acyclovir?
Creams (without prescription): free price, generally between €5 and €10
Tablets and other forms: reimbursed on medical prescription
Injectable forms, used in hospitals, are much more expensive.
When to consult?
It is recommended to consult a doctor if:
- symptoms persist or worsen
- the lesions are extensive or painful
- the infection affects the eye
- this is a first episode of genital herpes
- you are a person at risk
