Acivir 400: Uses, How It Works, Side Effects
Also known as: Acivir, Acivir 400 mg, Acivir 400 tablet, Acyclovir 400 mg, Aciclovir 400 mg
Acivir 400 is a prescription antiviral tablet containing 400 mg of acyclovir, used to treat infections caused by herpes viruses, such as cold sores, genital herpes, shingles and chickenpox. It slows the spread of the virus in the body but does not remove the virus for good. It works best when started early, after a doctor has prescribed it, and the full course should be finished.
- Active ingredient
- Acyclovir 400 mg
- Type of medicine
- Antivirals
- Used for
- Viral infections
- Starts working in
- Best started as early as possible after symptoms begin; follow the course your doctor gives
- Effect lasts
- Taken several times a day for the days your doctor prescribes; follow the label or your doctor's advice
- With or without food
- Can be taken with or without food; drink plenty of water
- Alcohol
- The NHS says you can drink alcohol as normal; ask your doctor if unsure
- Pregnancy
- Usually acceptable, but check with a doctor first; tell the doctor if you are pregnant or breastfeeding
- Habit-forming
- No
- Made by
- VERIFY on pack
Pharmacist review in progress. This page is based on the sources listed below and is being checked by our registered pharmacist.
On this page
- What is Acivir 400 used for?
- How does Acivir 400 work?
- How to take Acivir 400
- Side effects of Acivir 400
- Who should be careful
- Medicines and things that interact with Acivir 400
- If someone takes too much
- Storage
- Regulatory status in India
- Other brands with the same medicine
- Other strengths and forms
- Common questions
What is Acivir 400 used for?
Acivir 400 is used, on a doctor's advice, to treat infections caused by herpes viruses and, in some people with a weakened immune system, to help prevent them.
- Treating herpes simplex infections such as cold sores and genital herpes
- Treating shingles (herpes zoster) and chickenpox
- Helping to prevent these infections in people with a weakened immune system, when a doctor judges it suitable
How does Acivir 400 work?
Herpes viruses need to copy their genetic material inside body cells to multiply. Acyclovir is changed inside infected cells into a form that the virus mistakes for one of its building blocks, which stops the copying. The virus spreads less, but the medicine does not remove the virus from the body.
What happens in your body after you take it
You swallow the tablet
The tablet dissolves in the gut and acyclovir is absorbed into the blood. It can be taken with or without food, with plenty of water.
It reaches infected cells
Acyclovir travels in the blood to the skin, nerves and other tissues where herpes virus is active.
Only infected cells activate it
Inside cells that carry the virus, a virus enzyme converts acyclovir into its active form. Healthy cells make very little of this form.
Virus copying is blocked
The active form is taken in by the virus in place of a normal building block, so its genetic material cannot be copied and the virus spreads less.
The kidneys clear it
Acyclovir leaves the body mainly in the urine. Drinking enough fluid helps the kidneys, which matters more if kidney function is reduced.
How to take Acivir 400
Take Acivir 400 exactly as your doctor has prescribed or as printed on the pack. Your doctor decides how many tablets, how often and for how long.
- Start as soon as possible after the doctor prescribes it, because it works best early in an infection.
- It can be taken with or without food. Swallow it with water, and drink plenty of water during the course.
- Finish the full course even if you feel better, unless your doctor says otherwise.
- If you miss a dose, take it when you remember. If it is almost time for the next dose, skip the missed one. Do not take two doses together.
- Tell the doctor if you have kidney problems, because the amount or timing may need to change.
Side effects of Acivir 400
Most people take acyclovir without serious problems. Some side effects are common and mild, but a few need medical help.
Uncommon or mild
- Headache, dizziness or feeling faint, especially on standing up
- Nausea, vomiting, diarrhoea or stomach ache
- Skin rash or itching, or a skin reaction after sun exposure
- Tiredness or a high temperature
Rare but serious: get medical help
- Swelling of the face, lips, tongue or throat, an itchy raised rash or difficulty breathing (a severe allergic reaction). Get medical help immediately
- Yellow skin or eyes, itchy skin or unusual tiredness (possible liver problems)
- Passing much less urine than usual or none at all (possible kidney problems)
- Easy bruising, frequent infections or unusual tiredness (possible blood changes)
- Confusion, agitation or seizures
Who should be careful
Some people need to check with a doctor before taking Acivir 400, or need extra care while taking it.
When the label says not to use it
- Allergy to acyclovir, valaciclovir or any ingredient of the tablet
- Allergy to acyclovir or valaciclovir: do not take it
- Kidney problems: the dose may need to change, and plenty of fluids are important
- Dehydration from vomiting, diarrhoea or poor drinking: the kidneys can be affected
- Weakened immune system, such as HIV or chemotherapy: ask the doctor how the infection should be managed
- Pregnancy and breastfeeding: tell the doctor before taking tablets
- Dizziness or faintness: avoid driving, cycling or using machinery until you know how it affects you
- Genital herpes can still spread to a partner when there are no visible sores; ask the doctor about protecting a partner
- Surgery or dental work: tell the surgeon or dentist that you take it
Medicines and things that interact with Acivir 400
Acivir 400 can interact with some other medicines. Tell your doctor or pharmacist about everything you take, including herbal remedies and medicines bought over the counter.
- Probenecid (a gout medicine): it can change how acyclovir is handled by the body
- Cimetidine (a stomach acid medicine): it can change how acyclovir is handled by the body
- Mycophenolate mofetil (used after an organ transplant): the two medicines may not mix well
If someone takes too much
Taking one extra tablet by mistake is unlikely to cause problems, but larger amounts can be harmful, especially to the kidneys. If someone has taken much more than prescribed, call 112 or go to the nearest hospital and take the medicine pack with you.
Storage
Store in a cool, dry place in the original strip, away from light and moisture, and out of the reach of children. Do not use after the expiry date. Check the pack for the exact storage instructions.
Regulatory status in India
Approved for sale in India. Single-ingredient acyclovir is not on the CDSCO list of medicines banned under section 26A of the Drugs and Cosmetics Act. Acivir 400 is meant to be taken on a doctor's prescription; check the schedule printed on the pack.
Other brands with the same medicine
Acyclovir 400 mg tablets are sold under other brand names and as generic medicines. They contain the same medicine; check the label for the strength. Acyclovir is also sold as a cream and an eye ointment, which are different products.
Other strengths and forms
Acyclovir is also sold as a cream, an eye ointment and in other tablet strengths. The strength and form are printed on the pack and are not interchangeable, so check the label of the one you have.
Common questions
What is Acivir 400 used for?
Acivir 400 contains acyclovir, an antiviral used on a doctor's advice for infections caused by herpes viruses, such as cold sores, genital herpes, shingles and chickenpox. It slows the virus but does not remove it from the body.
Does Acivir 400 remove the herpes virus for good?
No. It slows the virus so that the infection can settle sooner, but the virus can stay in the body and return later. Ask your doctor what to expect and how to avoid passing genital herpes to a partner.
Why is it important to start Acivir 400 early?
Antivirals work best when taken soon after symptoms begin. For shingles, the NHS says tablets work best within 3 days of the rash appearing. See a doctor promptly rather than waiting, and follow the course the doctor gives.
Is Acivir 400 a prescription medicine?
Acyclovir tablets are meant to be taken on a doctor's prescription. Do not start, stop or change it without a doctor's advice, and do not share tablets with others.
Do I need to drink more water with Acivir 400?
Yes. Drinking plenty of water helps your kidneys clear the medicine, and this matters more if you have kidney problems. Tell your doctor if you are vomiting, have diarrhoea or cannot drink enough.
What should I do if I miss a dose of Acivir 400?
Take it when you remember. If it is almost time for the next dose, skip the missed one and carry on as usual. Never take two doses together to make up for a missed one.
Can I take Acivir 400 during pregnancy?
The NHS says aciclovir is usually acceptable in pregnancy, but you should check with a doctor first. Tell your doctor if you are pregnant, planning a baby or breastfeeding, so that they can weigh the benefits and risks.
What is the difference between Acivir 400 and acyclovir 400 mg?
Acivir is a brand name and acyclovir is the medicine inside it. Generic acyclovir 400 mg tablets contain the same active ingredient. Check the strength and ingredient list on the pack, and ask your doctor before switching products.
Sources
- Aciclovir. NHS (UK)
- Acyclovir. MedlinePlus, US National Library of Medicine
- Shingles. NHS (UK)
- ATC/DDD Index: J05AB01 Aciclovir. WHO Collaborating Centre for Drug Statistics Methodology
- List of drugs prohibited for manufacture and sale through gazette notifications under section 26A of the Drugs & Cosmetics Act 1940. Central Drugs Standard Control Organisation (CDSCO)