aciclovir at a glance
Medicine class
Direct-acting antiviral nucleoside analogue
Viruses targeted
Herpes simplex and varicella-zoster viruses
Available forms
Tablets, oral suspensions, cold-sore cream and intravenous infusion
Kidney considerations
Systemic aciclovir is cleared mainly by the kidneys; hydration and renal function are important
What is aciclovir used for?
Selected products are licensed for different herpes-virus infections and settings.
Oral products: herpes simplex infections, including genital herpes; suppression or prevention in selected people; chickenpox and shingles.
Cold-sore cream: herpes simplex infection of the lips and face.
Intravenous product: severe or specialist-managed herpes simplex and varicella-zoster infections, including herpes encephalitis and neonatal herpes.
How does aciclovir work?
In herpes-infected cells, aciclovir is converted to an active form that blocks viral DNA polymerase and stops viral DNA-chain formation, limiting further virus replication.
aciclovir preparations and strengths
Eye ointment
Route: Ophthalmic
Strengths: 30 mg/g
Oral suspension
Route: Oral
Strengths: 200 mg/5 mL, 400 mg/5 mL
Tablet
Route: Oral
Strengths: 200 mg, 400 mg, 800 mg
How to take aciclovir
Follow the product label or prescriber's instructions because administration differs by formulation.
Tablets may be swallowed with water; some can be dispersed in water first.
Maintain adequate fluid intake during oral treatment, particularly with reduced kidney function.
Shake oral suspension well and use the supplied oral-measuring device.
For cold-sore cream, wash hands before and after applying a thin film to affected and surrounding skin. Do not use it in the eyes, inside the mouth or vagina, or for genital or eye herpes.
Intravenous aciclovir is given as a slow infusion by healthcare professionals and must not be given as a rapid injection.
aciclovir side effects
Common or expected effects
- Oral treatment: headache, dizziness, nausea, vomiting, diarrhoea or abdominal discomfort
- Rash, itching or increased sensitivity to sunlight
- Tiredness or fever
- Cold-sore cream: brief burning or stinging, itching, dryness or flaking at the application site
Get urgent medical advice
- Allergic reaction with facial or throat swelling or breathing difficulty
- Kidney injury, including reduced urine output or renal pain
- Confusion, hallucinations, tremor, marked drowsiness or seizures
- Liver inflammation or jaundice
- Blood-cell changes causing unusual bruising, tiredness or frequent infections
aciclovir in pregnancy
Aciclovir can be used during pregnancy when clinically indicated. Available evidence has not identified an increased risk of birth defects. Discuss treatment with a prescriber or midwife, particularly for systemic treatment, genital herpes or chickenpox.
aciclovir while breastfeeding
Aciclovir is generally compatible with breastfeeding a full-term, healthy infant. Prevent the infant touching treated skin and seek specialist advice for premature or unwell infants.
aciclovir interactions
Topical aciclovir has no described clinically significant medicine interactions, but systemic treatment requires a complete medicines review.
Probenecid or cimetidine
May reduce renal clearance and increase aciclovir exposure.
Ciclosporin, tacrolimus or other nephrotoxic medicines
May increase kidney-injury risk, especially with intravenous treatment.
Lithium
High systemic exposure, particularly with intravenous aciclovir, may increase lithium toxicity.
Theophylline
Aciclovir may increase theophylline exposure.
Common questions about aciclovir
Answers are fully visible for fast scanning and source review.
Is aciclovir an antibiotic?
No. Aciclovir is an antiviral that acts against herpes viruses; antibiotics treat bacterial infections.
Does aciclovir cure herpes permanently?
It suppresses viral replication and helps control episodes or prevent recurrences, but does not remove latent herpes virus from the body.
Sources
These sources were used to prepare and review this medicine page.
Prepared and reviewed by the iatroX editorial team.