Medically reviewed by Alan Lucks | MD, Alan Lucks MDPC Private Practice - New York on January 6th, 2026.
Acyclovir is a cornerstone antiviral for managing herpes simplex virus (HSV) infections and varicella-zoster virus (VZV) conditions like shingles. Despite its long-standing use, dosing acyclovir correctly can be confusing because it depends on the type of infection, its severity, and patient-specific factors such as age and kidney health.
Getting the dose right matters. Too little may not entirely suppress the virus, risking flare-ups and transmission. Too much can increase side effects like nausea, headache, or kidney issues. This guide clearly breaks down acyclovir dosages, helping you understand how much to take and when to take it.
Form |
Strength |
Typical Adult Dose |
Typical Children’s Dose |
Frequency |
Route |
Maximum Daily Dose |
|---|---|---|---|---|---|---|
Tablet |
200 mg |
200 mg to 800 mg |
20 mg/kg/day (divided doses) |
3 to 5 times daily |
Oral |
4,000 mg/day |
Capsule |
400 mg |
400 mg to 800 mg |
20 mg/kg/day (divided doses) |
3 to 5 times daily |
Oral |
4,000 mg/day |
Injection |
50 mg/mL |
5 mg/kg |
5 mg/kg |
Every 8 hours |
IV |
15 mg/kg/day |
Ointment |
5% |
Apply 5 times daily |
Apply 5 times daily |
Topical |
Topical |
N/A |
For initial episodes in adults, acyclovir is typically prescribed at 400 mg orally three times a day for 7 to 10 days. Recurrences are often treated with 800 mg orally twice daily for 5 days. For chronic suppression, 400 mg twice daily may be recommended to reduce the frequency of outbreaks.
For cold sores, a common approach is 200 mg five times daily for 5 days. Early treatment at the first sign of symptoms can reduce healing time and severity.
Shingles treatment usually involves 800 mg orally, taken 5 times a day for 7 to 10 days. This higher dose helps control the more severe viral activity and nerve pain associated with shingles.
In children, acyclovir is dosed at 20 mg/kg orally four times daily for 5 days, ideally started within 24 hours of rash onset to reduce symptoms and complications.
Adults receive varying doses depending on the infection. For example, oral doses for herpes simplex infections range from 200 mg to 800 mg taken 3 to 5 times daily. Intravenous doses are reserved for severe infections or immunocompromised patients, typically 5 mg/kg every 8 hours.
It’s essential to take acyclovir exactly as prescribed, maintaining consistent intervals between doses to keep adequate drug levels in the bloodstream.
Children’s doses are generally weight-based, around 20 mg/kg per day, divided into 3 to 5 doses. For severe infections, intravenous administration may be necessary with close medical supervision.
If a dose is missed, take it as soon as remembered unless it is almost time for the next dose. Do not double up doses to catch up. Maintaining a regular dosing schedule is key to effective treatment.
The kidneys primarily eliminate Acyclovir. Patients with reduced kidney function require dose adjustments to prevent toxicity. This may involve lowering the dose or extending the interval between doses. Your healthcare provider will determine the best regimen based on kidney function tests.
Patients with weakened immune systems, such as those undergoing chemotherapy or with HIV, often need higher or more frequent dosing to control viral replication effectively. Close monitoring is necessary to balance efficacy and side effects.
Overdose symptoms can include nausea, vomiting, dizziness, confusion, and, in severe cases, kidney damage or seizures. If an overdose is suspected, seek emergency medical attention immediately.
Common side effects include headache, diarrhea, and fatigue. Severe allergic reactions are rare but require urgent care.
Take with plenty of water to help prevent kidney problems.
Complete the full course even if symptoms improve early.
Store medication at room temperature away from moisture and heat.
Inform your doctor about all medications and supplements to avoid interactions.
Consult your healthcare provider before starting or stopping acyclovir.
Understanding the correct dosage of acyclovir can be complex. Doctronic.ai offers a revolutionary AI-powered doctor service that provides personalized medical advice based on the latest peer-reviewed research. Whether you have questions about dosing schedules, side effects, or need a second opinion, Doctronic’s AI doctor is available 24/7 to help.
Additionally, Doctronic connects you with licensed physicians for telehealth video visits across all 50 states, offering convenient and affordable care for your antiviral treatment needs. Visit Doctronic.ai to get started with your personalized consultation on acyclovir dosage today.
Acyclovir can interact with certain drugs, especially those affecting kidney function. Always inform your healthcare provider about all medications and supplements you are taking.
Acyclovir is generally considered safe during pregnancy but should only be used under medical supervision.
Starting acyclovir at the earliest sign of symptoms improves effectiveness, especially for cold sores and chickenpox.
Most side effects are mild. If you experience severe symptoms such as a rash, difficulty breathing, or swelling, seek medical help immediately.
Yes. Doctronic.ai offers personalized, AI-driven medical advice and connects you with doctors for telehealth visits to discuss your medication and dosage needs.
Acyclovir remains a trusted antiviral for managing herpes and related viral infections. Correct dosing tailored to your condition and health status ensures the best outcomes and minimizes side effects. If you are unsure about how much acyclovir to take or need help adjusting your dose, expert guidance is just a click away with Doctronic.ai.
Understanding Acyclovir Uses and DosagesAcyclovir is a cornerstone antiviral for managing herpes simplex virus (HSV) infections and varicella-zoster virus (VZV) conditions [...]
Read More
