Aciclovir

What is aciclovir?

Aciclovir is an antiviral medication used to treat infections caused by herpes viruses. It doesn’t cure the infection but helps reduce symptoms and speed up healing[1]. 

What is aciclovir used to treat?

Aciclovir is licensed to treat[1]: 

• Treatment and prevention of recurrence of cold sores (Herpes simplex virus) 

• Treatment and prevention of recurrence of genital herpes 

• Chickenpox (Varicella zoster virus) 

• Shingles (Herpes zoster) 

• neonatal herpes simplex infection 

• Herpes encephalitis (brain inflammation caused by herpes virus) 

• Preventing herpes infections in people with weakened immune systems 

How does aciclovir work?

Aciclovir works by interfering with the virus’s DNA replication, preventing it from going and multiplying. This helps control the infection and reduces the severity and duration of symptoms[1]. 

Who can take aciclovir?

Most adults, children and babies can take aciclovir[1]. 

However, caution is needed if you: 

• Have kidney problems 

• Have ever had an allergic reaction to aciclovir 

• Are over 65 

• Have a weakened immune system 

• Are pregnant, trying to get pregnant or breastfeeding 

Always inform your doctor or pharmacist about any conditions you may have before you start treatment and always follow the instructions in the Patient Information Leaflet[2]. 

How do you take aciclovir?

Aciclovir tablets or liquid can be taken with or without food. You should drink plenty of fluids to protect your kidneys, especially if you are elderly, have kidney problems, or are on high doses[1].  

You should swallow the tablets whole with a drink of water and space your doses evenly throughout the day[1]. 

Aciclovir is available as an oral liquid. It should come with a syringe or spoon designed to hold the correct amount. If you do not have either, ask your pharmacist rather than using a kitchen teaspoon so that you take the correct dose. 

For the cream to treat cold sores, apply only to the affected areas as directed. Make sure you wash your hands before and after using the cream. 

What is the dosage of aciclovir?

Your dosage depends on the condition being treated, age, and kidney function. Your doctor will tell you how much to take and how often[1]. 

Topical creams for cold sores, genital herpes, and eye ointments are generally applied 5 times a day. Follow the instructions on the information leaflet on how to apply them 

Always follow your doctor’s instructions or the leaflet provided with your medicine[2]. 

Can you stop taking aciclovir?

Do not stop taking your medicine until the course is finished even if you feel better, unless advised by your doctor. Stopping too soon may allow the virus to return or worsen[1]. 

What do you do if you take too much aciclovir?

Taking an extra dose of aciclovir by accident is unlikely to cause harm. However, if you take too much for several days or a very large single overdose, it can be harmful, particularly to your kidneys. Contact your doctor, NHS 111, or go to a hospital immediately if you are worried or have taken a significant overdose. 

What do you do if you forget to take aciclovir?

If you miss a dose, take it as soon as you remember. If it's almost time for your next dose, skip the missed dose and continue with your regular schedule. Never take 2 doses at the same time[1]. 

What are the side effects of aciclovir?

The most common side effects of aciclovir include[1]: 

• Headache 

• Nausea or vomiting 

• Diarrhoea 

• Dizziness 

• Tiredness/fatigue 

• Skin reactions (rash, itching) 

 If you have a severe allergic reaction (swelling, difficulty breathing, rash). Call 999 or go to A&E immediately. 

If you experience any side effects, including those not listed, you are encouraged to report them via the Yellow Card Scheme or contact your doctor, pharmacist, or nurse. This information is intended as a summary for general awareness and does not replace professional medical advice. 

The information provided in the side effects section is not a comprehensive list of all possible side effects associated with this medication. For a complete list of side effects, please refer to the Patient Information Leaflet (PIL) provided with your medication or consult your healthcare professional[2]. 

Medicines you can and can’t take with aciclovir

Tell your doctor if you are taking, or have recently taken, any of the following, as they may interact with aciclovir[1]: 

• Probenecid (for gout) 

• Cimetidine (for ulcers) 

• Theophylline (for asthma) 

• Immunosuppressants (e.g., tacrolimus, cyclosporin) 

• Lithium (for bipolar disorder) 

• Mycophenolate mofetil 

Always inform your doctor or pharmacist about all medications and supplements you take before you start a new medicine, and follow the instructions in the Patient Information Leaflet[2]. 

Frequently asked questions about aciclovir

Can I drink alcohol while taking aciclovir? 
Yes, alcohol doesn’t interfere with aciclovir. However, alcohol can sometimes cause dehydration or worsen side effects like dizziness or nausea. It is generally advisable to limit alcohol while taking any medication, especially if you experience these effects[1]. 

Can I take aciclovir long-term? 
Yes, for people with frequent infections, doctors may prescribe it long-term to prevent recurrences[1]. 

Is it safe during pregnancy? 
Aciclovir is generally considered safe to use if needed during pregnancy after assessment by a doctor[1]. 

Can I drive while taking aciclovir? 
Yes, unless you feel dizzy, drowsy, or experience other side effects that could affect your ability to drive safely[1]. 

Will it affect my contraception? 

Aciclovir does not affect your contraception. However, if you are sick or have diarrhoea for more than 24 hours, your contraceptive pills may not protect you. Look at the leaflet in your pill packet to find out what to do[1]. 

For the official NHS guide to aciclovir, visit their website.