Aciclovir
The original antiviral for herpes, still widely prescribed, taken more often per day than valaciclovir and costing even less.
- Class
- Antiviral
- Sold as
- Sold as: Zovirax
- Prescription only
From the approved label
Aciclovir tablets
- Approved uses
- Herpes Zoster Infections: Acyclovir tablets, USP are indicated for the acute treatment of herpes zoster (shingles).
- Genital Herpes: Acyclovir tablets, USP are indicated for the treatment of initial episodes and the management of recurrent episodes of genital herpes.
- Chickenpox: Acyclovir tablets, USP are indicated for the treatment of chickenpox (varicella).
- Forms and strengths
- Acyclovir tablets USP, 800 mg containing 800 mg of acyclovir USP are blue, oval, biconvex tablets debossed with 'J' on one side and '50' on the other side.
- How it is taken
- Acute Treatment of Herpes Zoster: 800 mg every 4 hours orally, 5 times daily for 7 to 10 days.
- Genital Herpes: Treatment of Initial Genital Herpes: 200 mg every 4 hours, 5 times daily for 10 days.
- Chronic Suppressive Therapy for Recurrent Disease: 400 mg 2 times daily for up to 12 months, followed by re-evaluation.
- Alternative regimens have included doses ranging from 200 mg 3 times daily to 200 mg 5 times daily.
- Must not be used when
- Acyclovir tablets are contraindicated in patients who have had a demonstrated clinically significant hypersensitivity reaction [e.g., anaphylaxis, severe cutaneous adverse reactions (SCARs)] to acyclovir, valacyclovir, or any component of the formulation (see WARNINGS and ADVERSE REACTIONS).
- Interactions
- See CLINICAL PHARMACOLOGY: Pharmacokinetics.
- Warnings and precautions
- Acyclovir tablets are intended for oral ingestion only.
- Renal failure, in some cases resulting in death, has been observed with acyclovir therapy (see ADVERSE REACTIONS: Observed During Clinical Practice and OVERDOSAGE).
- Thrombotic thrombocytopenic purpura/hemolytic uremic syndrome (TTP/HUS), which has resulted in death, has occurred in immunocompromised patients receiving acyclovir therapy.
- Severe cutaneous adverse reactions (SCARs), including acute generalized exanthematous pustulosis (AGEP), drug reaction with eosinophilia and systemic symptoms (DRESS), Stevens-Johnson syndrome (SJS), toxic epidermal necrolysis (TEN), and erythema multiforme (EM) have been reported with acyclovir (see CONTRAINDICATIONS and ADVERSE REACTIONS).
- Common side effects
- Herpes Simplex: Short-Term Administration: The most frequent adverse events reported during clinical trials of treatment of genital herpes with acyclovir tablets 200 mg administered orally 5 times daily every 4 hours for 10 days were nausea and/or vomiting in 8 of 298 patient treatments (2.7%). Nausea and/or vomiting occurred in 2 of 287 (0.7%) patients who received placebo.
- Pregnancy
- Teratogenic Effects: Pregnancy Category B. Acyclovir administered during organogenesis was not teratogenic in the mouse (450 mg/kg/day, p.o.), rabbit (50 mg/kg/day, s.c. and IV), or rat (50 mg/kg/day, s.c.). These exposures resulted in plasma levels 9 and 18, 16 and 106, and 11 and 22 times, respectively, human levels.
- Label holder:
- Camber Pharmaceuticals, Inc.
- Label version:
This section reports the approved product information. The wording is condensed from the regulator's own summary, and the full document is linked under Sources.
Written by us
How it works
Aciclovir is taken up by cells infected with the virus and blocks the enzyme the virus uses to copy itself. Because uninfected cells take up far less of it, its effect is concentrated where the infection is, which is the reason a medicine this old is still in routine use.
Original and generic
Entirely generic. The label shown here comes from a generic manufacturer, because that is what pharmacies dispense.
What it costs
Cheaper than valaciclovir and among the least expensive prescriptions in any pharmacy. The trade-off is the number of doses per day, which is set out in the label.
How to get it legally
Prescription only as tablets. The topical cream for cold sores is sold without a prescription in many countries, which is a different product with a different label, and this page is about the tablets.
Comparison
See also
Questions
- Why take it several times a day?
- Because of how quickly it leaves the body. The dosing section states the schedule for each approved indication.
- Is the cream the same medicine?
- The same substance in a different product with its own approval and its own label. Creams for cold sores are sold over the counter in many countries; tablets are not.
- Does it cure herpes?
- No, and no label in this class claims that. The virus persists in nerve cells and the treatment acts on episodes and their frequency.
Sources
- Acyclovir: prescribing informationDailyMed, US National Library of Medicine. Label version 2 February 2026
- Drugs@FDA: ANDA203834US Food and Drug Administration
In this category
- ValaciclovirThe standard treatment for genital herpes, taken either as a short course during an outbreak or daily to reduce how often outbreaks occur.
- DoxycyclineThe first-line antibiotic for chlamydia in current European and British guidance, and an old, cheap, well-documented medicine.
- AzithromycinThe single-dose antibiotic that was once standard for chlamydia and has since moved down the guidance in most of Europe.
- Emtricitabine and tenofovir disoproxilPre-exposure prophylaxis: a daily tablet taken by people who do not have HIV, to prevent acquiring it. Prevention rather than treatment, with testing built into the label.