Acyclovir: uses, dosing, side effects & brands
Acyclovir is a herpes simplex virus nucleoside analog dna polymerase inhibitor sold in the U.S. under 6 brand and generic names, for chickenpox, herpes genitalis and herpes labialis. Below: what the FDA label says, every product that contains it, what the pills look like, and its recall record.
Key facts
- Drug class
- Herpes Simplex Virus Nucleoside Analog Dna Polymerase Inhibitor
- Treats (across its forms)
- Chickenpox, Herpes Genitalis and Herpes Labialis
- Available as
- Injectable · Topical · Capsule · Solution · Suspension · Tablet
- Sold as
- 6 products — Acyclovir Sodium, Zovirax and Acyclovir, and others
- Prescription?
- Prescription only
- Generic available?
- Yes
- Half-life
- about 2.5 to 3.3 hours
- What the pharmacy pays
- about $5 for a 30-count supply — not your price
How Acyclovir Sodium is dosed
From the FDA label for Acyclovir Sodium (application ANDA203701). Other acyclovir products — different forms, different strengths — are dosed differently. Follow the label for the one you were prescribed.
CAUTION - RAPID OR BOLUS INTRAVENOUS INJECTION MUST BE AVOIDED (see WARNINGS and PRECAUTIONS ). INTRAMUSCULAR OR SUBCUTANEOUS INJECTION MUST BE AVOIDED (see WARNINGS ). Therapy should be initiated as early as possible following onset of signs and symptoms of herpes infections. A maximum dose equivalent to 20 mg/kg every 8 hours should not be exceeded for any patient. Dosage HERPES SIMPLEX INFECTIONS MUCOSAL AND CUTANEOUS HERPES SIMPLEX (HSV-1 AND HSV-2) INFECTIONS IN IMMUNOCOMPROMISED PATIENTS Adults and Adolescents (12 years of age and older) 5 mg/kg infused at a constant rate over 1 hour, every 8 hours for 7 days. Pediatrics (Under 12 years of age) 10 mg/kg infused at a constant rate over 1 hour, every 8 hours for 7 days. SEVERE INITIAL CLINICAL EPISODES OF HERPES GENITALIS Adults and Adolescents (12 years of age and older) 5 mg/kg infused at a constant rate over 1 hour, every 8 hours for 5 days. HERPES SIMPLEX ENCEPHALITIS Adults and Adolescents (12 years of age and older) 10 mg/kg infused at a constant rate over 1 hour, every 8 hours for 10 days. Pediatrics (3 months to 12 years of age) 20 mg/kg infused at a constant rate over 1 hour, every 8 hours for 10 days . Neonatal Herpes Simplex Virus Infections (Birth to 3 months) 10 mg/kg infused at a constant rate over 1 hour, every 8 hours for 10 days. In neonatal herpes simplex infections, doses of 15 mg/kg or 20 mg/kg (infused…
Everything below is the FDA label for Acyclovir Sodium (injectable). Acyclovir is also sold as topical, capsule, solution, suspension and tablet, and those are different medicines to take — follow the label for the one you were prescribed.
Acyclovir Sodium side effects
The adverse reactions listed below have been observed in controlled and uncontrolled clinical trials in approximately 700 patients who received acyclovir at approximately 5 mg/kg (250 mg/m 2 ) 3 times daily, and approximately 300 patients who received approximately 10 mg/kg (500 mg/m 2 ) 3 times daily. The most frequent adverse reactions reported during administration of acyclovir were inflammation or phlebitis at the injection site in approximately 9% of the patients, and transient elevations of serum creatinine or BUN in 5% to 10% (the higher incidence occurred usually following rapid [less than 10 minutes] intravenous infusion). Nausea and/or vomiting occurred in approximately 7% of the patients (the majority occurring in nonhospitalized patients who received 10 mg/kg). Itching, rash, or hives occurred in approximately 2% of patients. Elevation of transaminases occurred in 1% to 2% of patients. The following hematologic abnormalities occurred at a frequency of less than 1%: anemia, neutropenia, thrombocytopenia, thrombocytosis, leukocytosis, and neutrophilia. In addition, anorexia and hematuria were observed. Observed During Clinical Practice In addition to adverse events reported from clinical trials, the following events have been identified during post-approval use of Acyclovir Sodium Injection in clinical practice. Because they are reported voluntarily from a population…
Who shouldn’t take Acyclovir Sodium
Acyclovir Sodium Injection is contraindicated for patients who develop hypersensitivity to acyclovir or valacyclovir.
Acyclovir Sodium drug interactions
See CLINICAL PHARMACOLOGY, Pharmacokinetics .
Every acyclovir product we track (6)
Same active ingredient — different manufacturer, form, price and FDA recall record. That last one is what our independent score measures.
| # | Drug | Rating | Type | Form | Generic? | Pharmacy pays | |
|---|---|---|---|---|---|---|---|
| 1 | 70/100 | Prescription | Injectable | Generic | $5 | View → | |
| 2 | 70/100 | Prescription | Topical | Generic | $5 | View → | |
| 3 | 56/100 | Prescription | Topical | Generic | $5 | View → | |
| 4 | Not yet rated | Prescription | Injectable | Generic | $5 | View → | |
| 5 | Not yet rated | Prescription | Topical | Generic | $5 | View → | |
| 6 | Not yet rated | Prescription | Tablet | Generic | $5 | View → |
What acyclovir pills look like
Imprint codes, colour and shape from the FDA’s labelling data. Match the imprint on your pill — or search any imprint.
| Imprint | Strength | Colour | Shape | Maker |
|---|---|---|---|---|
| J;50 | 800 mg | blue | oval | — |
| S042 | 800 mg | blue | capsule | — |
| Apotex;5307 | 800 mg | white | oval | — |
| Y213 | 800 mg | white | oval | — |
Acyclovir recalls
From the FDA Enforcement database. A recall covers specific lots — not the drug as a whole.
How long acyclovir keeps
The date on a sealed pack is not the only one: some acyclovir labels start a second clock once the product is opened or mixed, as short as 24 hours.
Does acyclovir expire? The in-use limits and storage rules from its labelsAcyclovir and breastfeeding
From LactMed, the US National Library of Medicine’s Drugs and Lactation Database — quoted, not rewritten.
Full LactMed record for acyclovir: levels in milk, effects in breastfed infants, and the drugs it would consider insteadEven with the highest maternal dosages, the dosage of acyclovir in milk is only about 1% of a typical infant dosage and would not be expected to cause any adverse effects in breastfed infants. Acyclovir is considered a treatment of choice for Herpes infections during breastfeeding. Topical acyclovir applied to small areas of the mother's body away from the breast should pose no risk to the infant. Only water-miscible cream or gel products should be applied to the breast because ointments may expose the infant to high levels of mineral paraffins via licking.
National Institute of Child Health and Human Development, record revised February 15, 2026. LactMed states its information is not a substitute for professional judgement.
What people report to the FDA about acyclovir
The FDA Adverse Event Reporting System (FAERS) collects reports from patients and clinicians. It holds 117,258 reports naming acyclovir, and the FDA flagged 72% of those reports as serious. The effects reported most often — leaving out reports about overdose, misuse or the condition being treated, which dominate the raw list for common medicines:
- fatigue8,596 reports
- diarrhoea7,617 reports
- nausea5,995 reports
- pneumonia5,897 reports
- pyrexia5,065 reports
- rash4,418 reports
- dyspnoea3,754 reports
- headache3,576 reports
Read these as a signal, not a rate. A report does not mean acyclovir caused the effect — anyone can file one, and many describe people taking several medicines for several conditions. Crucially there is no denominator: FAERS does not record how many people took the drug, so these counts cannot be turned into “X% of patients” — a bigger number often just means a more widely used or more talked-about drug. Duplicates exist, and publicity drives reporting. For what is actually established, read the FDA label section above.
Source: openFDA drug/event (FAERS), retrieved August 25, 2026.
How long acyclovir stays in your system
The elimination half-life of acyclovir is about 2.5 to 3.3 hours. Acyclovir is cleared almost entirely by the kidneys — 62% to 91% of a dose leaves the body as unchanged drug — so the half-life tracks kidney function closely. The IV label tabulates it by creatinine clearance: 2.5 hours at CrCl above 80, 3 hours at 50–80, 3.5 hours at 15–50, and 19.5 hours in anuric patients, roughly an eightfold increase in severe kidney failure. Older adults reach higher plasma levels than younger adults, which the label attributes to age-related decline in renal function rather than to age itself; no separate geriatric half-life is given. There is no active metabolite that outlasts the parent — the only major urinary metabolite named is 9-carboxymethoxymethylguanine (up to 14.1% of the dose), and the label does not report a half-life for it. Liver impairment is not addressed in the pharmacokinetics section, consistent with renal rather than hepatic elimination. No extended-release oral acyclovir is marketed in the US; tablets, capsules, oral suspension and IV all reflect the same short elimination half-life. One drug effect worth naming: probenecid taken with acyclovir lengthens the mean half-life and raises overall exposure.
Acyclovir Tablets, USP — FDA prescribing information, Clinical Pharmacology (DailyMed) ↗Half-life is how long the body takes to clear half a dose. It is not the same as how long a drug test can detect it, and it varies with age, kidney and liver function.
Related calculators
Frequently asked questions
What is Acyclovir Sodium?
Acyclovir Sodium is a herpes simplex virus nucleoside analog dna polymerase inhibitor used to treat Chickenpox, Herpes Genitalis, Herpes Labialis, Herpes Zoster Ophthalmicus.
What kind of drug is acyclovir?
The FDA classifies acyclovir as a herpes simplex virus nucleoside analog dna polymerase inhibitor. If you are checking whether it is safe to combine with something else, the class is what matters — two drugs from the same class usually should not be stacked.
How long does acyclovir stay in your system?
The elimination half-life of acyclovir is about 2.5 to 3.3 hours — that is how long the body takes to clear half of a dose. Acyclovir is cleared almost entirely by the kidneys — 62% to 91% of a dose leaves the body as unchanged drug — so the half-life tracks kidney function closely. The IV label tabulates it by creatinine clearance: 2.5 hours at CrCl above 80, 3 hours at 50–80, 3.5 hours at 15–50, and 19.5 hours in anuric patients, roughly an eightfold increase in severe kidney failure. Older adults reach higher plasma levels than younger adults, which the label attributes to age-related decline in renal function rather than to age itself; no separate geriatric half-life is given. There is no active metabolite that outlasts the parent — the only major urinary metabolite named is 9-carboxymethoxymethylguanine (up to 14.1% of the dose), and the label does not report a half-life for it. Liver impairment is not addressed in the pharmacokinetics section, consistent with renal rather than hepatic elimination. No extended-release oral acyclovir is marketed in the US; tablets, capsules, oral suspension and IV all reflect the same short elimination half-life. One drug effect worth naming: probenecid taken with acyclovir lengthens the mean half-life and raises overall exposure. Half-life is not the same as how long a drug test can detect the drug, and it varies with age, kidney and liver function.
Can you take acyclovir with other medicines?
It depends on the medicine. We check it against the FDA labels rather than guessing: our interaction checker searches each drug's own label for the other and quotes what it says, naming the section it came from. Run acyclovir against whatever else you take — and remember that a label not naming a drug is not the same as that combination being safe.
What brand names is acyclovir sold under?
We track 6 acyclovir-containing products in the U.S.: Acyclovir Sodium, Zovirax, Acyclovir, Acyclovir in Sodium Chloride 0.9% Preservative Free, Avaclyr and Sitavig. They are the same active ingredient; they differ in form, manufacturer, price and FDA recall record.
What forms does acyclovir come in?
Across the brands we track, acyclovir is currently marketed as injectable, topical, capsule, solution, suspension and tablet, per the FDA's National Drug Code Directory. Each form is dosed differently — follow the label for the exact product you were prescribed.
Is there a generic acyclovir?
Yes. Our catalog lists 3 generic acyclovir products alongside the brand versions. A generic has the same active ingredient and must meet the FDA's bioequivalence standard; it usually costs less. Ask your pharmacist which one your plan covers.
Has acyclovir been recalled?
The FDA's Enforcement database lists 1 recall record whose product description mentions acyclovir. The most recent: acyclovir sodium (Feb 5, 2026). A recall applies to specific lots, not to the drug as a whole — check the record for the affected lot numbers.
Cite this page
- APA
- pharmaranks. (2026, July 24). Acyclovir: uses, dosing, side effects & brands. https://pharmaranks.com/drugs/acyclovir
- MLA
- “Acyclovir: uses, dosing, side effects & brands.” pharmaranks, 24 July 2026, https://pharmaranks.com/drugs/acyclovir.
We summarise public FDA and NIH sources — for a clinical claim, cite the primary source we link to as well.
Sources: FDA openFDA drug label, National Drug Code Directory, and Enforcement (recall) database. This page reproduces public FDA data and is not medical advice. Dosing is set by your prescriber.
Read the full FDA label for acyclovir on DailyMed (NIH) ↗.