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Quick summary

Type of medicine




Active Ingredient


Effective within

Depends on the condition being treated

Works by

Killing or stopping the growth of viruses

Side effects

Headache, dizziness, nausea, vomiting, diarrhea, rash, photosensitivity, fatigue

Medication details


Aciclovir 400 mg Tablets are a recognized antiviral medication widely employed for addressing various viral conditions. These tablets contain the active ingredient Aciclovir, known for its effectiveness in inhibiting the replication of certain viruses. With a standard dosage of 400 mg, this medication is commonly utilized in the management of herpes simplex infections, herpes zoster (shingles), and varicella-zoster (chickenpox) infections. As with any medication, it's essential to adhere to prescribed guidelines and consult a healthcare professional for accurate usage. Potential side effects and interactions with other medications are crucial aspects to consider, making informed decision-making paramount.


Dosage: The standard dosage is 400 mg, typically taken orally, unless otherwise advised by a healthcare professional.
Frequency: The frequency of administration depends on the specific viral condition being treated. Common dosing intervals may range from two to five times daily, as directed by your healthcare provider.
Timing: It's crucial to adhere to a consistent schedule when taking Aciclovir. To ensure optimal effectiveness, try to space out doses evenly throughout the day, following the prescribed dosing intervals.
With or Without Food: Aciclovir can usually be taken with or without food. However, if you experience stomach upset, taking it with a meal or snack might help alleviate discomfort.
Stay Hydrated: Ensure you drink an adequate amount of fluids while taking Aciclovir to support proper absorption and minimize the risk of dehydration.
Completion of Course: Even if symptoms improve, it's imperative to complete the full course of medication as prescribed by your healthcare professional. This helps prevent the recurrence of the viral infection.
Missed Dose: If you miss a dose, take it as soon as you remember. However, if it's close to the time for your next dose, skip the missed dose and resume your regular schedule. Avoid doubling the dose to make up for a missed one.
Consultation: Before starting or discontinuing Aciclovir treatment, consult your healthcare provider. They can provide personalized guidance based on your medical history and condition.


Aciclovir 400 mg Tablets contain aciclovir as the active ingredient. Each tablet comprises 400 mg of aciclovir. In addition to the active ingredient, the tablets contain other components, including cellulose, microcrystalline, sodium starch glycolate, povidone, silica colloidal anhydrous, and magnesium stearate.

Side Effects

It's important to be aware of potential side effects associated with Aciclovir 400 mg Tablets. While not everyone experiences them, they may include:
- Headache
- Dizziness
- Nausea or vomiting
- Diarrhoea
- Stomach pains
- Rash
- Photosensitivity (skin reaction after light exposure)
- Itching
- Fatigue
- Fever and fainting upon standing (postural hypotension)
- Allergic reactions (rash, swelling, shortness of breath, collapse)
Uncommon or rare effects on blood, liver, and other body systems
If you notice any side effects, consult your doctor or pharmacist. You can also report side effects through the Yellow Card Scheme for the safety of others using this medicine.


Before taking Aciclovir 400 mg Tablets, consider the following:
Do not take if you are allergic to Aciclovir or its ingredients.
If you have kidney problems or are over 65 years old, consult your doctor or a pharmacist before use.
If you are Pregnant, breastfeeding, or planning pregnancy, Seek medical advice before taking this medicine.
If you experience drowsiness or impaired concentration, avoid driving or operating machinery.

Drink plenty of water while you are taking this medicine.

Medically reviewed and published

  • This page was medically reviewed by Dr Sohaib Imtiaz, Clinical Lead on Aug 24, 2023, 3:30 pm

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Start a consultation for your condition, select a treatment option, and our in-house clinicians will review and prescribe if suitable. Expect your order within 1-3 working days.

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Please read our FAQs page to find out more.

Can Aciclovir 400 mg Tablets be used to prevent herpes outbreaks?

Yes, Aciclovir 400 mg Tablets can be prescribed to prevent recurrent herpes outbreaks. This includes cold sores, genital herpes, and other herpes simplex infections. Your doctor will determine the appropriate dosage and duration based on your medical history and condition.

Can I take Aciclovir 400 mg Tablets if I'm pregnant or breastfeeding?

If you are pregnant, breastfeeding, planning to become pregnant, or suspect you may be pregnant, it's essential to consult your doctor before taking Aciclovir 400 mg Tablets. They will provide guidance on whether this medication is suitable for your situation.

Are there any interactions between Aciclovir 400 mg Tablets and other medications?

Yes, there can be interactions between Aciclovir 400 mg Tablets and other medications. It's crucial to inform your doctor or pharmacist about all the medicines you are currently taking, including prescription, non-prescription, and herbal remedies. Certain medications, such as probenecid and cimetidine, may interact with Aciclovir 400 mg Tablets.

How long should I continue taking Aciclovir 400 mg Tablets?

The duration of Aciclovir 400 mg Tablets treatment varies depending on the condition being treated and your doctor's recommendations. For example, treatment for chickenpox and shingles typically lasts seven days, while treatment for cold sores and genital herpes may last five days or longer. Always follow your doctor's instructions for the prescribed duration.

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