If you have been prescribed aciclovir for a cold sore, shingles or genital herpes, you may be wondering whether it is safe to take with your other medicines. For people searching BNF aciclovir ibuprofen nephrotoxicity, the key point is that aciclovir is mainly cleared by the kidneys. Medicines that can affect kidney function, including ibuprofen and other NSAIDs, may increase the risk of kidney related side effects, particularly with regular or high dose use, dehydration or existing kidney problems.
Aciclovir does not have a long list of serious medicine interactions. The most important considerations are usually your kidney function, the dose of aciclovir you are taking and any other medicines that may affect how aciclovir is cleared from the body.
Much of the information available online about aciclovir interactions is aimed at hospital patients receiving intravenous treatment or people taking medicines after a transplant. This is different from someone taking aciclovir tablets or using aciclovir cream for a cold sore, shingles or genital herpes.
This guide focuses on the questions people commonly have about aciclovir and other medicines. It covers ibuprofen, paracetamol, antihistamines and some antibiotics, as well as the differences between aciclovir cream and tablets. It also explains why staying hydrated matters and when you should speak with a healthcare professional. The information is based on NHS guidance and the approved product information.
Key things to know when taking aciclovir
- The NHS identifies three medicines that may interact with aciclovir tablets: probenecid, cimetidine and mycophenolate mofetil.
- No clinically significant medicine interactions are known for aciclovir cream or eye ointment.
- You can generally drink alcohol while taking aciclovir. The NHS advises that you can eat and drink as normal while taking it.
- Paracetamol can generally be taken alongside aciclovir for pain or fever.
- No clinically significant interaction is generally expected between aciclovir and cetirizine, other antihistamines or amoxicillin.
- Drinking enough water while taking aciclovir tablets is important, particularly if you have kidney problems or are at risk of dehydration.
- Aciclovir is mainly cleared by the kidneys, so kidney function is an important consideration when assessing potential interactions.
Which Medicines Actually Interact With Aciclovir?
It helps to separate the medicines into different groups because the level of concern can vary depending on the aciclovir product you are using and your individual health.
The medicines the NHS names for aciclovir tablets
NHS guidance identifies three medicines that may interact with aciclovir tablets: probenecid, cimetidine and mycophenolate mofetil.
If you take any of these medicines, tell your doctor or pharmacist before starting aciclovir. They can consider your other treatment, kidney function and the type and dose of aciclovir you have been prescribed. In some cases, monitoring or an adjustment to treatment may be appropriate.
| Medicine | Used for | Why it matters |
|---|---|---|
| Probenecid | Gout | Slows the removal of aciclovir by the kidneys, so levels in the blood rise and stay higher for longer |
| Cimetidine | Stomach ulcers and reflux | Also reduces how quickly the kidneys clear aciclovir, raising exposure |
| Mycophenolate mofetil | Immunosuppression after an organ transplant | Competes for the same route of clearance, so the effects of both can be increased |
Notice the common thread. All three act on the kidneys, not on the liver. None of them is a medicine most people with a cold sore will be taking, which is why the interaction question resolves quickly for the majority of readers.
Interactions that mainly matter in hospital and specialist care
Professional references such as the British National Formulary include some additional cautions. These are more relevant to people receiving high dose or intravenous aciclovir, those with kidney problems, or people receiving specialist treatment. They are less likely to be relevant to a short course of oral aciclovir at home.
The main concerns include:
- Medicines that can affect the kidneys, such as aminoglycoside antibiotics including gentamicin and amikacin, amphotericin B, ciclosporin, tacrolimus and tenofovir. Taking several medicines that can affect kidney function may increase the risk of kidney related problems.
- Medicines whose levels may be affected by aciclovir, including theophylline, which is used to treat some respiratory conditions. Zidovudine, an HIV medicine, has also been associated with increased drowsiness and lethargy when taken with aciclovir.
These interactions are particularly important with high dose intravenous aciclovir, existing kidney impairment and in people receiving transplant or immunosuppressive treatment. In these situations, healthcare professionals will usually monitor treatment and kidney function as appropriate.
If you are receiving specialist treatment or have kidney problems, make sure your healthcare team knows about all the medicines you take.
Aciclovir Cream and Eye Ointment
The interaction picture is simpler with aciclovir cream and eye ointment. No clinically significant medicine interactions are known for these topical products.
Only a small amount of aciclovir is absorbed into the bloodstream when it is applied to the skin. This means the kidney related concerns associated with aciclovir tablets are much less relevant to topical treatment.
If you are using aciclovir cream for a cold sore, medicine interactions are generally not a major concern. However, always follow the instructions supplied with your particular product.
Can You Take Ibuprofen With Aciclovir?
This is a common question, particularly because people may come across information about kidney toxicity when searching for aciclovir and ibuprofen. The answer depends on your health, how much ibuprofen you take and how long you take it.
Ibuprofen is not listed by the NHS among the main medicines that may interact with aciclovir, and it is not treated as a specific interaction in the same way as medicines such as probenecid or cimetidine. Occasional use of a standard dose of ibuprofen may be suitable for some adults taking a short course of aciclovir, provided they have normal kidney function and are adequately hydrated.
The reason for caution is that both medicines can be relevant to kidney function in different ways. Aciclovir is mainly cleared through the kidneys, while NSAIDs such as ibuprofen can reduce blood flow to the kidneys. The risk may be greater if you take regular or high doses of an NSAID, have kidney problems or become dehydrated.
It is therefore worth speaking with a pharmacist or prescriber before taking ibuprofen with aciclovir if you:
- Take ibuprofen, naproxen, diclofenac or another NSAID regularly.
- Have kidney disease or reduced kidney function.
- Are older or have other health conditions that may affect your kidneys.
- Are vomiting, have diarrhoea or are otherwise struggling to drink enough fluids.
- Have been prescribed a high dose of aciclovir or are receiving intravenous treatment.
If you need a painkiller while taking aciclovir, paracetamol may be a simpler option for many people, provided it is suitable for you.
Paracetamol, Cetirizine and Amoxicillin With Aciclovir
These medicines are commonly searched alongside aciclovir, and the available guidance is generally reassuring. However, your individual health and other medicines still matter.
Paracetamol
Paracetamol can generally be taken alongside aciclovir when a suitable painkiller is needed. NHS guidance states that it is safe to take paracetamol with aciclovir.
Headache can occur while taking aciclovir tablets, and paracetamol may be used to help manage pain when appropriate. If you are choosing between paracetamol and ibuprofen while taking aciclovir, paracetamol does not have the same kidney related considerations as NSAIDs such as ibuprofen.
Always follow the recommended paracetamol dose and check whether any other medicines you take also contain paracetamol.
Cetirizine and other antihistamines
No clinically significant interaction is known between aciclovir and cetirizine. Antihistamines are not among the main medicines highlighted by the NHS as interacting with aciclovir.
The same generally applies to other commonly used antihistamines, including loratadine and fexofenadine. Sedating antihistamines, such as chlorphenamine, may cause drowsiness.
Aciclovir can also cause dizziness or tiredness in some people. If you take aciclovir with a medicine that makes you sleepy and notice that you feel particularly drowsy or dizzy, avoid driving or using machinery until you feel well enough.
Amoxicillin and other antibiotics
No clinically significant interaction is known between aciclovir and amoxicillin. They work in different ways and are used to treat different types of infection, so one does not cancel out the effect of the other.
Some antibiotics used in hospital, including aminoglycosides such as gentamicin and amikacin, require more consideration because they can affect kidney function. This is different from taking a standard course of oral amoxicillin at home.
If you have been prescribed an antibiotic while taking aciclovir, tell your doctor or pharmacist about all the medicines you are taking so they can check that the combination is appropriate for you.
| Everyday medicine | With aciclovir | Notes |
|---|---|---|
| Paracetamol | Suitable | The usual choice for aciclovir-related headache |
| Ibuprofen and other NSAIDs | Usually fine occasionally | Ask about regular or high-dose use, kidney problems, or if you are dehydrated |
| Cetirizine, loratadine, fexofenadine | No known interaction | Watch for combined drowsiness with sedating antihistamines |
| Amoxicillin and other oral antibiotics | No known interaction | Different target organism entirely |
| Omeprazole and most reflux medicines | No known interaction | Cimetidine is the exception and is flagged separately |
| The combined pill and most contraceptives | No known interaction | Aciclovir does not reduce contraceptive effectiveness |
| Herbal remedies and supplements | Tell your prescriber | Not automatically safe just because they are sold without a prescription |
Can You Drink Alcohol on Aciclovir?
Yes. NHS guidance states that you can eat and drink normally while taking aciclovir, including alcohol. There is no known direct interaction between alcohol and aciclovir, and alcohol is not expected to stop the medicine from working.
There are two sensible points to keep in mind. First, aciclovir can cause headache, dizziness and nausea in some people, and alcohol can cause similar symptoms. Drinking heavily when you are already feeling unwell may therefore make you feel worse. Second, staying hydrated is important. Alcohol can contribute to dehydration, and maintaining good fluid intake is particularly important when taking aciclovir tablets.
So, rather than alcohol itself being the main concern, it is sensible to avoid heavy drinking, particularly if you are unwell, vomiting or not drinking enough water.
Why the NHS Says to Drink Plenty of Water With Aciclovir
The advice to drink plenty of water appears in aciclovir patient information, and there is a good reason for it.
Aciclovir is removed from the body mainly through the kidneys, largely unchanged. It has limited solubility in urine, so when someone is dehydrated and their urine becomes more concentrated, aciclovir can, rarely, form crystals in the kidney tubules. This can contribute to kidney problems, particularly with high doses, intravenous treatment, existing kidney impairment or dehydration.
Drinking enough fluid helps the kidneys clear the medicine. NHS guidance places particular emphasis on staying well hydrated if you have kidney problems.
There is no official requirement to drink a specific number of glasses of water each day while taking aciclovir, so avoid relying on an exact target unless your healthcare professional has given you one. Pale yellow urine can be a useful general sign that you are adequately hydrated, although it is not a medical test.
Illness itself can also make dehydration more likely. If you are vomiting, have diarrhoea, or are struggling to eat and drink because you feel unwell, speak to a pharmacist or healthcare professional for advice.
Who Needs Extra Caution With Aciclovir
Aciclovir is suitable for many people, but some situations need extra care. Tell your prescriber or pharmacist if any of the following apply to you:
- Kidney problems, because aciclovir is cleared mainly through the kidneys and the dose may need to be adjusted.
- Older age, particularly if there is a possibility of reduced kidney function.
- Dehydration caused by illness, hot weather, vomiting or diarrhoea.
- A weakened immune system, for example because of HIV, chemotherapy or immunosuppressant medicines. In these situations, medical advice is particularly important.
- A previous allergic reaction to aciclovir or valaciclovir, which is closely related to aciclovir.
- Certain neurological conditions, particularly when high dose or intravenous aciclovir is being considered.
- Pregnancy or breastfeeding. Aciclovir may be prescribed in these situations when appropriate, but speak to your prescriber before using it.
For children, the appropriate formulation and dose depend on their age, condition and individual circumstances. Aciclovir may be prescribed for conditions such as chickenpox or shingles, but children should be treated according to specific prescribing guidance rather than adult dosing information.
Aciclovir Side Effects
Side effects are more commonly reported with aciclovir tablets than with cream or ointment. With topical treatment, mild burning or stinging at the application site can occur.
Common side effects of the tablets
Possible side effects include headache, dizziness, nausea, vomiting, diarrhoea, stomach discomfort, rash, itching and tiredness. Not everyone experiences these effects.
If you feel dizzy or faint, avoid driving, cycling or using machinery until you feel well again. Speak to a pharmacist, prescriber or doctor if a side effect concerns you, is severe or does not improve. Do not stop prescribed treatment unless a healthcare professional advises you to do so.
Serious side effects: when to get help
Serious side effects are uncommon, but some symptoms need prompt medical attention. Seek medical advice if you think you may be experiencing a serious reaction while using, or shortly after using, aciclovir.
- Signs of a serious allergic reaction, such as swelling of the throat or tongue, a widespread or raised itchy rash, or difficulty breathing.
- Possible liver problems, which can include unusual tiredness, itching or yellowing of the skin or whites of the eyes.
- Possible kidney problems, such as being unable to pass urine or passing much less urine than usual.
- Possible blood cell changes, which can cause unusual tiredness, easy bruising or repeated infections.
If you miss a dose, take it when you remember unless it is almost time for your next dose. In that situation, skip the missed dose and continue with your usual schedule. Do not take two doses together to make up for a missed dose.
If you accidentally take more than prescribed, seek advice from a pharmacist, prescriber or appropriate medical service, particularly if you develop symptoms such as nausea or vomiting.
Aciclovir Tablets and Aciclovir Cream for Cold Sores
These are different products for different situations, and the distinction affects the interaction question directly.
| Aciclovir 5% cream | Aciclovir tablets | |
|---|---|---|
| Typical use | Cold sores on the lips and face; some types also for genital herpes | Cold sores, shingles, chickenpox, genital herpes, and prevention in some people |
| How it is obtained | Some types available from pharmacies without a prescription | Prescription only |
| Interactions | None known | Three medicines flagged by the NHS, plus kidney-related cautions |
| Side effects | Uncommon; mild burning or stinging | More likely, and listed above |
| When to seek advice | If a cold sore has not healed after 9 days of use, or 10 days for genital herpes | If symptoms worsen or do not improve as expected |
Timing matters more than strength with cold sores. Treatment works best when it is started at the first tingle or itch, before the blister appears, which is why many people keep a treatment at home rather than waiting for an appointment once a sore has erupted. Cream should not be used inside the mouth or nose, in or near the eyes, or internally. Wash your hands before and after applying it, both to protect the area and to avoid spreading the virus.
Which product is appropriate depends on where the infection is, how severe it is, how often outbreaks occur and your general health. Treatment suitability depends on an individual clinical assessment, and your prescriber will determine the appropriate treatment.
Getting Aciclovir in the UK and What It Costs
Aciclovir tablets are a prescription only medicine, so an appropriate clinical assessment is required before they can be supplied. An online consultation can be completed at home and reviewed by a UK registered prescriber, with treatment dispensed by a GPhC registered pharmacy.
When completing an assessment, tell the prescriber about everything you take, including medicines bought over the counter, supplements and herbal products. These can be easy to overlook but may still be relevant when checking whether treatment is suitable.
The price confirmed at consultation is the price that applies. Valaciclovir is converted into aciclovir in the body and has some similar interactions, but the medicines are not identical. Always check the patient information leaflet supplied with your medicine and follow the advice given by your prescriber or pharmacist.
Valtrex is a branded version of valaciclovir and contains the active ingredient valaciclovir.
Medical Disclaimer
This article provides general information and does not constitute medical advice. It does not replace advice from a qualified healthcare professional or the patient information leaflet supplied with your medicine, which contains product specific information.
Aciclovir tablets are a prescription only medicine and should only be used under the supervision of an appropriately qualified prescriber. Whether aciclovir is suitable for you depends on your individual circumstances, medical history and other medicines. Your prescriber will determine the appropriate treatment, and individual responses can vary.
Always tell your prescriber or pharmacist about every medicine you take, including medicines bought without a prescription, supplements and herbal remedies. Seek medical advice if you experience a serious or concerning side effect.
This page explains common aciclovir interactions in general terms and should not be used as a substitute for an individual medicine interaction check.
