Acyclovir: What It’s For, How to Use It & Side Effects

Acyclovir is a medication with antiviral action indicated for the prevention or treatment of skin infections or mucosal infections caused by the Herpes simplex or Herpes zoster virus. This medication does not cure infections, however, but reduces symptom intensity and duration. It can help reduce the burning sensation or formation of blisters.

This medication helps to heal the blisters faster, helping to prevent the formation of new wounds. It can decrease itching and relieve pain that these blisters can cause during an outbreak or after they have healed. Acyclovir can decrease the risk of the virus spreading to other parts of the body in immunocompromised people, as this population is at risk for developing more severe infections.

Acyclovir can be found in pharmacies in pill form (in doses of 200 mg or 400 mg), as a cream or as an ointment. It should be used as prescribed by the doctor. In addition, acyclovir can be as an IV medication, administered in a hospital setting.

What it is for

Acyclovir is indicated for the treatment of infections caused by the following viruses:

• Herpes zoster virus, also known as shingles

• Varicella zoster virus (chickenpox)

• Herpes simplex virus (genital herpes and cold sores)

In addition, this medication is also used to treat herpes meningoencephalitis.

How acyclovir works

Acyclovir is an active substance that acts by blocking the mechanisms involved with virus multiplication. This helps to prevent the spread of the virus to other cells. This medication, however, does not kill the virus nor does it cure an infection, but it can reduce the duration of infection and the intensity of symptoms.

How to use it

Acyclovir should be used in the doses prescribed by the doctor. Dosing will vary depending on the virus being treated, the patient's health status and the route of the medication, which include:

1. Acyclovir cream (50 mg/g)

Acyclovir cream is indicated for the treatment of skin or mucosal infections caused by the Herpes simplex virus, including genital or oral herpes. It can be used at the onset of symptoms.

This cream should be applied as a layer over the blister or skin wound 5 times per day, every 4 hours. Applications can be skipped when sleeping. You should wash your hands with water and mild soap before and after applying the cream to prevent worsening or spreading of the infection.

Treatment with acyclovir cream should continue for at least 4 days for oral herpes, or 5 days for genital herpes. If your wounds do not heal, treatment can extend for another 5 days. If the wounds persist for over 10 days, you should follow-up with your doctor.

Acyclovir cream should not be used on the eyes, as there is a specific ophthalmic ointment available for eye infections.

2. Acyclovir pills (200 or 400 mg)

Acyclovir pills should be used orally in the dosing and duration prescribed by a doctor. If you forget to take a dose at the right time, take it as soon as you remember, or skip it if you are close taking your next scheduled dose. You should never double your dose to compensate for a forgotten pill.

Dosing should be prescribed by a doctor and will vary depending on the health problem being treated.

People who are immunocompromised or have intestinal absorption problems may benefit from an increase to 400 mg or from IV administration. Dosing for babies, children and older adults should be adjusted according to weight and health status.

3. Ophthalmic ointment (30 mg/g)

Acyclovir ophthalmic ointment is indicated for the treatment of keratitis, a corneal infection caused by the Herpes simplex virus.

Before using this ointment, you should wash your hands with water and mild soap. To apply it, press your finger on your under-eye and pull it down to create a pocket. Then squeeze the ointment tube to apply a 1 centimeter ribbon of ointment in the space between the lower lid and the eye. This ointment is applied 5 times per day, every 4 hours. Be sure to close your eye for 1 to 2 minutes after application and to wash your hands once again with water and mild soap.

You should monitor for healing and continue to apply this ointment for at least 3 days.

Possible side effects

Use of the ophthalmic ointment can lead to cornea wounds and a light, temporary sensation of stinging after application, local irritation or conjunctivitis. In some cases, the cream can cause a temporary burning sensation, mild skin dryness, peeling or itching. The side effects of oral acyclovir are classified below.

Common side effects

The most frequently reported adverse effects of aciclovir include:

• Nausea

• Vomiting

• Diarrhea

• Headache

• Malaise

Serious side effects (Call Doctor)

Rare but serious adverse reactions require prompt medical evaluation:

• Unusual bleeding or bruising: This may indicate blood disorders such as thrombotic thrombocytopenic purpura.

• Seizures or confusion: Neurotoxicity symptoms may include agitation, hallucinations, and seizures, particularly in elderly patients or those with renal impairment.

• Swelling: Swelling in the face, feet, or legs, or changes in urination, can be signs of acute kidney injury.

Drug interactions

Several medications can interact with aciclovir, potentially affecting how the drug works or increasing the risk of side effects.

• Probenecid and Cimetidine: These medications can increase the amount of acyclovir in the blood by reducing its elimination through the kidneys.

• Nephrotoxic Drugs: Combining acyclovir with other medicines that can harm the kidneys increases the risk of acute kidney injury. This includes nonsteroidal anti-inflammatory drugs (NSAIDs) such as diclofenac, ibuprofen, and piroxicam, as well as aminoglycosides and vancomycin.

• Mycophenolate Mofetil: While significant interaction is rare, caution is advised when used in combination therapies that affect immune suppression levels.

Who should not use it

Acyclovir should not be used by people with an allergy to acyclovir, valacyclovir, propilenoglycol, or any of the components in the medication formula. It is also not recommended for pregnant or breastfeeding women or by women looking to become pregnant, unless prescribed by a doctor.

You should avoid using contact lenses when treating with ophthalmic ointment.