Medically reviewed by Jessica Swirble, PharmD
Last updated on April 17, 2025
Drug Information | Side Effects | Use & Dosage | Request an Online Prescription
Acyclovir is an antiviral medication used primarily to treat infections caused by certain types of viruses. It treats cold sores around the mouth (caused by herpes simplex), shingles (caused by herpes zoster), and chickenpox.
Acyclovir is primarily used to treat conditions such as:
It may also be used to treat outbreaks of genital herpes and to prevent recurrent outbreaks.
Acyclovir works by interfering with viral DNA synthesis, which reduces the virus's ability to replicate and spread. This helps to decrease the severity of infections and speed up the healing process.
Acyclovir can be taken in different forms, depending on the specific needs:
The dosage and duration of treatment depend on the condition being treated, its severity, and your response to the medication.
Follow your healthcare provider's instructions regarding dosage and schedule. Do not exceed the prescribed dose or duration of treatment without consulting your provider.
The effectiveness of acyclovir and the time it takes to notice improvement can vary among individuals. Improvement in symptoms can usually be observed within a few days of starting the medication, but it may take longer to fully recover from the infection.
Continue taking acyclovir as prescribed even if you start feeling better. Do not abruptly stop the medication, as it may lead to a return of the infection.
While acyclovir is primarily used for managing viral infections, healthcare providers may sometimes prescribe it off-label for other viral infections not listed above.
Discuss any alternative uses of acyclovir with your healthcare provider.
Acyclovir is available in the following dosage forms:
Generic versions of acyclovir are available, providing cost-effective treatment options.
Acyclovir is a prescription medication. You will need a valid prescription from a licensed healthcare provider to obtain this medication.
The use of acyclovir can lead to various side effects in some individuals.
Common mild side effects of acyclovir use include:
More severe side effects of acyclovir use can include:
If you experience any severe or concerning side effects while taking acyclovir, contact your healthcare provider right away.
What should I tell my healthcare provider before using acyclovir?
Tell your healthcare provider about any existing medical conditions, allergies, or other medications you are taking before starting treatment with acyclovir. This includes prescription drugs, over-the-counter medications, and dietary supplements, as they may interact with acyclovir.
Tell your provider if you are taking these medications or supplements:
You should also mention medical conditions such as:
If you are pregnant, planning to become pregnant, or breastfeeding, consult your healthcare provider before using acyclovir to assess potential risks and benefits.
Take acyclovir exactly as prescribed by your healthcare provider. Do not exceed the recommended dose or duration of treatment.
Acyclovir should be taken with or without food based on your healthcare provider's advice. It is important to follow their instructions for optimal effectiveness.
Stay hydrated while taking acyclovir, especially if you are taking higher doses, to help prevent kidney issues.
In case of an acyclovir overdose, seek medical attention immediately. Symptoms of overdose may include agitation, loss of consciousness, and seizures. If you suspect an overdose, contact the poison control helpline at 1-800-222-1222 or call emergency services.
Acyclovir is available in the following forms:
The typical starting dose of acyclovir varies depending on the condition being treated, the severity of symptoms, and individual patient factors. It is important to follow your healthcare provider's instructions regarding dosage and administration.
For herpes simplex virus infections, the typical starting dose may be:
For shingles (herpes zoster), the typical dose may be:
The dosage may be adjusted based on the response and tolerance to the medication. Your healthcare provider will determine the most appropriate dose based on your medical history, current medications, and response to the medication.
Acyclovir should be taken exactly as prescribed by your healthcare provider. Do not exceed the recommended dose or duration of treatment without consulting your provider.
If you have any questions about your dosage or need adjustments, contact your healthcare provider for guidance. If you need immediate medical advice or assistance, consider scheduling an online doctor appointment through a platform like Sesame.
If you miss a dose of acyclovir, take it as soon as you remember unless it is close to the time for your next scheduled dose. In that case, skip the missed dose and continue with your regular dosing schedule. Do not double the dose to make up for a missed one.
Maintain a consistent dosing schedule to ensure the effectiveness of acyclovir in managing your viral infection.
Continue taking acyclovir as prescribed by your healthcare provider, even if you start feeling better. Do not stop the medication abruptly without consulting your provider, as it may lead to a recurrence of symptoms or other complications.
Complete the full course of treatment as directed to minimize the risk of relapse.
If you have any concerns or questions about your medication, discuss them with your healthcare provider for personalized guidance and recommendations.
Store acyclovir according to the instructions provided by your healthcare provider or pharmacist. Keep it at room temperature, away from moisture, heat, and light. Ensure the container is tightly closed and out of reach of children.
Do not use expired medication or medications that appear damaged or discolored. If you have any questions about storage, consult your healthcare provider or pharmacist for guidance.