Verified
I started on the same evening that the tingling began. The discomfort did not disappear immediately, but the sores stayed smaller than during my previous episode and healed within the week.
13 Sep 2026
Aciclovir
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Active ingredient
Aciclovir
Aciclovir is an antiviral tablet for adults with herpes infections, including genital herpes and selected herpes zoster regimens. It is also used to suppress frequent genital herpes recurrences and for herpes infections in people with reduced immunity when prescribed. The dose is stated on the pack — follow the leaflet.
Description
Aciclovir is an antiviral tablet. It is used in adults for herpes simplex infections, including genital herpes, and may be used for long-term suppression of recurrent episodes. The dose is stated on the pack — follow the leaflet.
Composition
Each Aciclovir tablet contains aciclovir, an antiviral medicine from the nucleoside analogue class. It acts against herpes simplex virus type 1, herpes simplex virus type 2, and varicella-zoster virus.
The medicine does not remove herpes virus from the body. It limits viral multiplication during active infection, which can shorten the course of lesions and reduce pain when treatment starts early. FDA prescribing information describes aciclovir as selectively activated in virus-infected cells, where it interferes with viral DNA production. [1]
For recurrent herpes, treatment works best when started at the first familiar warning signs, such as tingling, burning, itching, or local sensitivity before visible sores develop.
A practical detail often missed is hydration. Aciclovir leaves the body through the kidneys, and adequate fluid intake is useful during treatment, especially for older adults or anyone taking other medicines that can affect kidney function.
Dosage and usage
Aciclovir tablets are swallowed with water. The dose is stated on the pack — follow the leaflet. The dose and course depend on whether treatment is for a first herpes episode, a recurrence, or long-term suppression.
Common adult regimens used in clinical guidance include:
- Initial genital herpes: the dose is stated on the pack — follow the leaflet.
- Recurrent genital herpes: the dose is stated on the pack — follow the leaflet.
- Suppressive treatment for frequent recurrences: the dose is stated on the pack — follow the leaflet.
- Kidney impairment: lower doses or longer dosing intervals may be required.
A first genital herpes episode can be more painful and longer-lasting than later recurrences. Prescribers may extend treatment if new lesions continue to appear after the initial course.
Take doses at evenly spaced times. For a three-times-daily schedule, spacing doses across waking hours helps keep antiviral levels stable. If a dose is missed, take it when remembered unless the next dose is close. Do not double the next dose.
Set reminders for morning, mid-afternoon, and bedtime when using a three-times-daily regimen. Missing several doses may allow viral activity to return before the skin has healed.
Tablets should be swallowed whole. Crushing tablets is unnecessary and can leave an unpleasant taste. People who have difficulty swallowing should discuss suitable administration options with their prescriber before starting treatment.
How it works
After swallowing a tablet, aciclovir enters infected cells and is converted into its active form by viral enzymes. The active compound blocks viral DNA polymerase, an enzyme the herpes virus needs to reproduce. Human cells are affected far less because they do not activate aciclovir in the same targeted way.
This is why Aciclovir is useful for herpes viruses but does not treat bacterial infections, fungal infections, or viral illnesses such as influenza.
Aciclovir reduces viral shedding during treatment. It can also reduce the number of recurrent genital herpes outbreaks when taken as suppressive therapy. The World Health Organization includes aciclovir among antiviral options for genital herpes management, with treatment choice guided by the type of episode, recurrence pattern, and immune status. [2]
The main limitation is timing. Starting treatment after lesions have already crusted or begun healing may bring less benefit than starting during the first day of symptoms.
A recurring sore in the same area may be easier to recognise than a first episode. New, severe, widespread, or unusually painful lesions need clinical assessment because diagnosis changes the treatment plan.
Indications
Aciclovir is used for:
- Initial or recurrent genital herpes
- Suppression of frequent genital herpes recurrences
- Herpes infections in people with reduced immunity when prescribed for that purpose
- Selected herpes zoster regimens when the prescriber chooses tablet-based treatment
Comparison
Aciclovir is one of several oral antiviral approaches used for herpes infections. The best option depends on recurrence frequency, kidney function, convenience, and the clinical reason for treatment.
| Antiviral approach | Dosing pattern | Practical difference |
|---|---|---|
| Aciclovir | Often two to three daily doses for herpes simplex regimens | Long-established option with flexible episodic and suppressive use |
| Valaciclovir | Often once or twice daily | Converted to aciclovir in the body and may be more convenient |
| Famciclovir | Regimen varies by indication | Alternative antiviral with different activation and dosing schedules |
Valaciclovir can suit people who find frequent dosing difficult. Aciclovir remains a well-established choice when a prescriber wants a familiar antiviral with extensive clinical use.
No oral antiviral completely eliminates future herpes recurrences. Suppressive therapy can reduce their frequency, yet outbreaks may still occur. The decision to use daily treatment is often based on how often episodes happen, how severe they are, and whether they affect sexual wellbeing or quality of life.
Contraindications
- Serious allergic reaction to aciclovir or valaciclovir
- Known kidney disease or a history of kidney injury
- Dehydration from vomiting, diarrhoea, fever, or poor fluid intake
- Older age, where kidney function may be reduced
- Pregnancy or breastfeeding, where treatment choice should be tailored to the infection and stage of pregnancy
- Neurological conditions that could make confusion or drowsiness harder to assess
Aciclovir may interact with medicines that affect kidney function or its elimination. Probenecid and cimetidine can increase aciclovir exposure. Medicines with potential kidney toxicity, including tacrolimus, ciclosporin, aminoglycoside antibiotics, and some anti-inflammatory pain medicines, can increase the need for renal monitoring.
Aciclovir product information highlights dose adjustment for impaired renal function because drug accumulation raises the chance of kidney and neurological adverse effects. [3]
When this is not for you
This medication is not for you if you have had a serious allergic reaction to aciclovir or valaciclovir.
Talk to a doctor before using it if you have kidney disease, may be dehydrated, are older, are pregnant or breastfeeding, or have a neurological condition that could make confusion or drowsiness difficult to assess.
Tell your doctor about medicines that affect the kidneys, including probenecid, cimetidine, tacrolimus, ciclosporin, aminoglycoside antibiotics, and some anti-inflammatory pain medicines.
Mention every regular medicine before starting Aciclovir, including anti-rejection treatment, pain medicines, and over-the-counter anti-inflammatory tablets. The interaction concern is often kidney clearance rather than a direct conflict in the stomach.
Side effects
Most people tolerate oral aciclovir well. The more common effects are usually mild and settle without stopping treatment.
Possible side effects include:
- Headache
- Nausea
- Diarrhoea
- Stomach discomfort
- Tiredness
- Mild skin rash or itching
Kidney-related side effects are less common but more significant. They are more likely with dehydration, high doses, older age, pre-existing kidney disease, or medicines that also place strain on the kidneys. Reduced urine output, marked flank pain, unusual confusion, or severe weakness require prompt medical attention.
Neurological effects such as agitation, tremor, hallucinations, confusion, or drowsiness are uncommon. They occur more often when aciclovir accumulates because kidney clearance is reduced.
Nausea is often easier to manage when the tablet is taken after a light meal. This does not reduce aciclovir’s antiviral action.
A rash with facial swelling, wheezing, blistering, or peeling skin can indicate a serious allergic or skin reaction. Aciclovir should not be continued in that situation.
Common mistakes
Several avoidable errors make Aciclovir less useful.
- Starting too late: Waiting until lesions are fully developed may reduce the benefit of episodic treatment.
- Stopping after one improved day: Viral activity can continue after pain begins to ease. Complete the prescribed course.
- Doubling a missed dose: This raises side-effect risk without restoring the missed timing.
- Using another person’s regimen: A recurrence, first episode, shingles episode, and immune-related infection do not always use the same schedule.
- Ignoring reduced urine output: This can be an early warning of kidney stress, especially during dehydration.
- Assuming treatment prevents all transmission: Aciclovir lowers viral activity but does not guarantee that the virus cannot be passed on.
Some people also mistake every genital irritation for herpes. Thrush, bacterial skin conditions, dermatitis, and sexually transmitted infections can resemble a recurrence. A change in the usual pattern deserves assessment rather than repeated self-treatment.
What doctors say
In clinical practice, doctors often separate two goals: treating an active episode and preventing repeated episodes. A short course may be enough for occasional recurrences. Daily suppression may be considered when outbreaks are frequent, painful, emotionally disruptive, or linked with repeated transmission concerns.
Doctors also look at symptom timing. People who can recognise their early prodrome often get more value from episodic treatment because they begin therapy before lesions fully develop. A tablet started after several days of worsening sores has less opportunity to alter the episode.
Kidney function changes the prescription. A standard dose can become excessive when renal clearance is low, even if the person has used aciclovir before without difficulty. This matters after dehydration, acute illness, or a new kidney diagnosis.
Aciclovir can reduce genital herpes transmission risk when used as part of a broader plan, though it does not make transmission impossible. Condoms reduce risk but do not cover every area where herpes can shed. The Centers for Disease Control and Prevention states that suppressive antiviral therapy reduces recurrence frequency and can lower transmission risk in symptomatic HSV-2 infection. [4]
Frequently asked questions
How quickly does Aciclovir start working?
Aciclovir begins inhibiting viral replication after it is absorbed, yet symptom relief is gradual rather than immediate. People often notice fewer new lesions or reduced burning within several days when treatment starts early. The FDA prescribing information, revised in 2024, supports its use for herpes simplex episodes but does not promise the same response time for every person. [5] Healing speed also depends on whether the episode is a first infection, a recurrence, or associated with reduced immunity. Response varies between patients.
Can Aciclovir cure herpes permanently?
Aciclovir does not remove herpes simplex virus from nerve cells, where the virus can remain inactive between episodes. It treats active viral replication and can prevent or reduce recurrences during suppressive use. WHO guidance published in 2016 describes antiviral therapy as symptom and recurrence management rather than a permanent cure. Episodes may return after treatment stops, though their frequency varies widely between individuals.
Can Aciclovir 400 mg be used every day?
Daily use is prescribed for suppressive treatment of recurrent genital herpes in selected people. A commonly used suppressive schedule is 400 mg twice daily, though kidney function and the person’s infection history affect the final regimen. The CDC’s 2021 sexually transmitted infections guidance reports that suppressive therapy can reduce recurrent episodes substantially in people with frequent symptomatic HSV-2. Treatment is reviewed periodically to see whether the recurrence pattern has changed.
Can I take Aciclovir with food?
Aciclovir tablets can be taken with or without food. Taking a dose after food may help if nausea or stomach discomfort occurs. EMA product information issued in 2023 advises attention to hydration and renal function because the medicine is cleared through the kidneys. Food does not replace the need for regular fluid intake.
Does Aciclovir prevent passing herpes to a partner?
Suppressive aciclovir can reduce viral shedding and lower transmission risk, but it cannot remove that risk completely. Transmission can occur when there are no visible lesions because asymptomatic shedding is possible. WHO guidance from 2016 supports combining antiviral treatment with symptom awareness and barrier protection strategies. Avoiding sexual contact during outbreaks or prodromal symptoms remains a practical measure.
Is Aciclovir suitable during pregnancy?
Aciclovir may be used during pregnancy when the clinical benefit supports treatment, especially when herpes management affects maternal or neonatal risk. The decision depends on the type of herpes infection, gestational stage, recurrence history, and planned delivery care. The FDA pregnancy information for aciclovir, updated in 2024, does not support casual self-selection of a regimen during pregnancy. Obstetric care should guide the dose and duration.
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Comparison
Compare all medications for AntibioticsAciclovir: Reviews and Experiences
4
Based on 4 reviews
Verified
I used suppressive treatment after having outbreaks almost monthly. I had a mild headache during the first few days, then nothing noticeable. I still had one small recurrence during a stressful period, so the result was helpful but not perfect.
2 Sep 2026
Verified
The tablets were easy to take, but I felt nauseated when I used them before breakfast. Taking them after food solved that. I did miss an afternoon dose once, so I started using a phone reminder.
26 Aug 2026
Verified
I had reduced kidney function and my dose schedule needed adjusting. I was glad that this was discussed early because I had assumed the standard schedule suited everyone.
17 Aug 2026
Sources
- U.S. Food and Drug Administration (2024). Zovirax (acyclovir) tablets, capsules and suspension: Prescribing Information.
- World Health Organization (2016). WHO guidelines for the treatment of genital herpes simplex virus.
- electronic Medicines Compendium (emc) (2023). Aciclovir 400 mg Tablets: Summary of Product Characteristics.
- Centers for Disease Control and Prevention (2021). Sexually Transmitted Infections Treatment Guidelines, 2021.
- U.S. Food and Drug Administration (2024). Acyclovir: Drug label information.
