Itchy, painful blisters in the mouth area – every third German has had to struggle with cold sores. Means of choice against this herpes is then usually a cream with the active ingredient aciclovir, whereby the symptoms can be relieved. But aciclovir is also effective against other diseases caused by herpes viruses – for example, shingles or genital herpes. We explain what you need to be aware of when treating with aciclovir and what side effects may occur.
Mode of action: Inhibition of viral replication
Aciclovir is a so-called nucleoside analogue. This means that its chemical structure resembles a building block of the DNA of the herpes virus. When the virus replicates in an infected human cell and duplicates its DNA for this purpose, the aciclovir molecule can be incorporated instead of the “correct” building block. This then leads to the virus replication being interrupted. In this way, the active ingredient can alleviate and shorten the course of herpes infections. In this context, aciclovir is effective against herpes simplex virus type 1 and type 2 (HSV-1 and HSV-2), as well as against the varicella zoster virus, which also belongs to the group of herpes viruses.
Application of aciclovir
Aciclovir is used for the following conditions caused by herpes viruses:
- Labial herpes (herpes labialis).
- Genital herpes (genital herpes)
- Shingles (herpes zoster)
- Corneal inflammation of the eye
- Inflammation of the brain (encephalitis)
In addition, aciclovir can be used in severely immunocompromised patients – such as after an organ transplant – to prevent HSV infections. More rarely, the active ingredient is also used to treat chickenpox (varicella) in immunocompromised individuals.
Aciclovir as an ointment
Aciclovir ointment is used to relieve the pain and itching of cold sores and is available over the counter at pharmacies. The cream should be applied to the affected area every four hours until the blisters crust over. The duration of treatment is usually five to a maximum of ten days. In addition, an ointment containing aciclovir can be used to support the treatment of genital herpes. For the treatment of corneal inflammation caused by herpes viruses, there is a special eye ointment that must be prescribed by an ophthalmologist. During treatment, a strip of ointment about one centimeter long is usually placed in the lacrimal sac every four hours. The duration of treatment depends on the course of the disease – after healing of the inflammation, the ointment should continue to be applied for at least three days.
Dosage of aciclovir
Depending on the disease to be treated, aciclovir can be used in different dosage forms and dosages: In the form of tablets containing 200, 400, or 800 milligrams of active ingredient, aciclovir is used for genital herpes and shingles, as well as for severe courses of corneal inflammation. Please follow the instructions of your doctor or the package leaflet regarding dose and application! In the case of genital herpes and corneal inflammation, 400 milligrams of aciclovir are usually taken three to four times a day, whereas in the case of shingles a higher dosage of up to 4,800 milligrams a day divided into six individual doses is usually required. The duration of treatment is usually seven to ten days – but it is important that therapy is started as soon as possible after the onset of symptoms.
Aciclovir as prophylaxis
In particular, patients with severely weakened immune systems who are at increased risk for herpes infection can be treated prophylactically with aciclovir. In addition, prophylactic use of aciclovir may be considered in patients with frequently recurring, severe genital herpes. The dose here is usually between 400 and 1,600 milligrams per day.
Infusion therapy for severe disease
For severe conditions such as encephalitis caused by herpes viruses, aciclovir may be given as an infusion. Infusion therapy with aciclovir may also be considered in cases of severely painful genital herpes or when severe complications such as pneumonia occur with chickenpox disease. Herpes infections in immunocompromised patients are also frequently treated with aciclovir infusions.Compared with use in the form of tablets, infusions are usually much more effective – but hospitalization is usually necessary.
Contraindications and precautions
Aciclovir must not be used if you are hypersensitive to the active substance. Caution should be exercised in patients with renal impairment because aciclovir is excreted by the kidney. Thus, with impaired renal function, there may be delayed excretion of aciclovir, which is why a lower dosage is usually required in these cases.
Side effects of aciclovir
Aciclovir is a relatively well-tolerated active ingredient – side effects usually occur only at high doses or during infusion therapy. This is because crystals from the active ingredient can then form in the urine, causing damage to the kidneys. Therefore, you should drink enough during treatment with aciclovir. In addition, the following side effects may occur:
- Allergic reactions such as skin rash
- Nausea and vomiting
- Headache or dizziness
- Confusion, impaired consciousness, or hallucinations
- Change in blood count and liver and kidney values.
- Burning, irritation or redness of the skin or conjunctiva with topical treatment with an ointment or cream containing aciclovir.
- Irritation of the veins at the infusion site, as well as inflammation – especially if the infusion accidentally leaks into the tissue.
For a detailed list of possible side effects, please refer to the package insert.
Drug interactions
Drug interactions may occur if you take medications that affect kidney activity – for example, probenicid (used to treat gout), cimetidine (used to reduce stomach acid), or theophylline (used to treat respiratory conditions such as asthma) – during treatment with aciclovir. In addition, concomitant treatment with the active ingredients mycophenolate mofetil and ciclosporin (used to suppress the immune system after transplantation) may interact with aciclovir. Therefore, always inform your doctor about all medications you need to take regularly!
Aciclovir during pregnancy and breastfeeding
In animal studies, the use of aciclovir during pregnancy has led to malformations of the fetus. However, there is no evidence that the active ingredient also has adverse effects on the unborn child in humans. Since there are no adequate studies on this, aciclovir should only be used during pregnancy after strict consideration of the benefits and risks. However, it is known that aciclovir passes into breast milk. Therefore, aciclovir should not be used during breastfeeding. If treatment with aciclovir is necessary during lactation, it may be possible to discontinue breastfeeding for the duration of use.
