Aciclovir for Viral Infections (Zovirax)
Comprehensive guide to aciclovir (Zovirax): uses, dosage, side effects, and precautions for treating herpes and shingles effectively.
Aciclovir is an antiviral medication primarily used to treat infections caused by varicella-zoster virus (chickenpox and shingles) and herpes simplex virus (cold sores and genital herpes). It works by inhibiting viral DNA replication, reducing symptom severity and preventing spread.
About aciclovir
Aciclovir, also known as acyclovir in the US and marketed as Zovirax®, is a synthetic purine nucleoside analogue with selective activity against herpes simplex virus types 1 and 2 (HSV-1, HSV-2) and varicella-zoster virus (VZV). It prevents viruses from multiplying, thereby alleviating infection severity and halting progression. This medication is particularly valuable for individuals with weakened immune systems, where it can prevent infections altogether.
| Type of medicine | An antiviral medicine |
|---|---|
| Used for | Viral infections in adults and children |
| Also called | Acyclovir (in US); Zovirax® |
| Available as | Tablets, dispersible tablets, oral liquid medicine |
While topical forms like creams treat mild cases such as cold sores, oral tablets are essential for severe infections. Intravenous forms are used in hospitalized patients or immunocompromised individuals. Aciclovir does not eradicate the virus but controls outbreaks effectively.
Key facts about aciclovir
- Aciclovir is taken orally with or without food, spaced evenly throughout the day.
- Typical courses last 2-10 days; complete the full course to prevent recurrence.
- Hydration is crucial to avoid dehydration and kidney issues.
- Doses range from 200 mg to 800 mg, 3-5 times daily, based on infection type and patient factors.
- Not suitable for all; caution in kidney impairment or pregnancy.
Who can and cannot take aciclovir tablets
Most adults and children over 2 years can take aciclovir for appropriate infections. It is safe for pregnant and breastfeeding women when benefits outweigh risks, as it reduces neonatal herpes transmission.
Who can take aciclovir
- Adults and children treating or preventing HSV or VZV infections.
- Immunocompromised patients (e.g., HIV, transplant recipients).
- Neonates with confirmed HSV under specialist care.
Who cannot take it
- Those with hypersensitivity to aciclovir or valaciclovir.
- Caution in severe kidney disease; dose adjustment needed.
How and when to take aciclovir
Follow your doctor’s instructions precisely. Read the patient information leaflet (PIL) for full details on usage and side effects.
Dosage
Dosage varies by condition:
| Condition | Typical Adult Dose | Duration |
|---|---|---|
| Shingles | 800 mg 5 times daily | 7-10 days |
| Genital herpes (initial) | 200 mg 5 times daily or 400 mg 3 times daily | 5-10 days |
| Cold sores | 200 mg 5 times daily | 5 days |
| Chickenpox (children) | 20 mg/kg (max 800 mg) 4 times daily | 5 days |
| Suppression (recurrent genital herpes) | 400 mg twice daily | 6-12 months |
Children under 2: specialist dosing. Elderly or kidney-impaired: reduce dose.
Timing and administration
- Space doses evenly (e.g., every 4-6 hours).
- Take with water; stay hydrated (2-3 liters daily).
- Swallow tablets whole or disperse in water; shake liquid well.
- Continue full course even if symptoms improve.
If you miss a dose, take it soon unless near next dose; never double up.
Common questions about aciclovir
How long does it take to work?
Symptoms often improve within 2-5 days; full course prevents relapse.
Can I drink alcohol?
Yes, in moderation; alcohol does not interact but dehydration risk increases.
Is it safe in pregnancy?
Yes, category B; standard doses for genital herpes reduce transmission risk.
Side effects of aciclovir
Most people tolerate aciclovir well, but side effects occur in some. Consult PIL for full list.
| Common side effects | What to do |
|---|---|
| Feeling sick (nausea), vomiting, stomach ache | Stick to simple foods – avoid fatty or spicy meals |
| Itchy rash, feeling hot | Speak with your doctor if troublesome |
| Headache | Drink plenty of water; use painkiller. See doctor if persists |
| Diarrhea | Drink fluids to avoid dehydration |
Serious side effects (rare): Kidney problems (reduced urine, swelling), neurological effects (confusion, tremors), severe allergic reactions. Seek immediate medical help.
Reporting side effects
In UK, use Yellow Card scheme; in US, FDA MedWatch.
How to cope with side effects
- Nausea: Take with food; ginger tea helps.
- Headache: Paracetamol (acetaminophen); hydrate.
- Rash: Antihistamines; avoid irritants.
- Monitor kidney function if at risk.
Pregnancy and breastfeeding
Aciclovir is commonly used in pregnancy for genital herpes (400 mg three times daily for 5 days) to prevent neonatal transmission. It passes into breast milk in small amounts but is considered safe. Consult your doctor.
Other medicines and aciclovir
Inform your doctor of all medications:
- Mycophenolate mofetil: Increases aciclovir levels.
- Probenecid: Prolongs effects.
- Nephrotoxic drugs (e.g., aminoglycosides): Kidney risk.
- No major food interactions.
Common questions
Can I take it with other herpes treatments?
Yes, but follow medical advice; not with valaciclovir usually.
Does it prevent transmission?
Reduces viral shedding but use condoms and avoid contact during outbreaks.
Further information
- Read PIL thoroughly.
- Store below 25°C; discard expired medicine.
- For topical info, see separate leaflets on aciclovir cream.
Frequently Asked Questions (FAQs)
Q: Can aciclovir cure herpes?
A: No, it controls symptoms and outbreaks but does not cure the lifelong virus.
Q: Is aciclovir safe for children?
A: Yes, dosed by weight for chickenpox; not for under 2 without specialist advice.
Q: What if I forget a dose?
A: Take as soon as remembered unless near next dose; do not double.
Q: Can I drive while taking it?
A: Yes, unless dizziness occurs.
Q: How does it work?
A: Converted to active form by viral enzyme, inhibiting DNA polymerase and chain termination.
References
- Aciclovir for viral infections (Zovirax) — Patient.info. 2023-01-09. https://patient.info/medicine/aciclovir-for-viral-infections-zovirax
- ZOVIRAX (Acyclovir) Label — U.S. Food and Drug Administration (FDA). 2019. https://www.accessdata.fda.gov/drugsatfda_docs/label/2019/018603s030lbl.pdf
- Acyclovir — StatPearls, NCBI Bookshelf, National Library of Medicine (NIH). 2023. https://www.ncbi.nlm.nih.gov/books/NBK542180/
- Acyclovir (oral route, intravenous route) — Mayo Clinic. 2023. https://www.mayoclinic.org/drugs-supplements/acyclovir-oral-route-intravenous-route/description/drg-20068393
- Acyclovir: Uses, Interactions, Mechanism of Action — DrugBank Online. 2023. https://go.drugbank.com/drugs/DB00787
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