Allopurinol

What is allopurinol?

Allopurinol is a medicine that lowers the levels of uric acid in the blood. Too much uric acid can lead to painful conditions like gout or kidney stones, or cause complications during cancer treatment[1].  

It belongs to a group of drugs called xanthine oxidase inhibitors, which help reduce the production of uric acid in the body[1]. 

What is allopurinol used for?

Allopurinol is most commonly used to treat or prevent gout, a type of arthritis caused by uric acid crystals building around the joints. It can also be prescribed for uric acid and calcium oxalate renal stones kidney stones, or high uric acid levels caused by cancer chemotherapy[1]. 

Allopurinol is a preventative medicine. It is normally prescribed 2-4 weeks after a gout flare has settled, however your doctor or pharmacist may recommend starting during a flare alongside acute treatment if flares are more frequent[1]. 

How does allopurinol work?

Allopurinol works by inhibiting an enzyme called xanthine oxidase which the body uses to make uric acid from hypoxanthine (natural substances found in food and cells). By reducing uric acid levels, allopurinol helps prevent gout flare-ups, reduce the risk of uric acid and calcium oxalate kidney stones, and protect the kidneys during cancer chemotherapy[1]. 

Who can take allopurinol?

Allopurinol is suitable for most adults. It’s also sometimes used for children with specific conditions like cancer-related high uric acid under the care of a specialist. However, it may not be suitable for people who have had an allergic reaction to allopurinol or any of the excipients listed as part of the formulation[1].  

Individuals who are pregnant or breastfeeding, or are taking medicines that interact with allopurinol (see below), should speak to their doctor or pharmacist first before taking[1]. 

Some ethnicities may have a greater risk of allopurinol related hypersensitivity reactions, such as Stevens-Johnson syndrome. If you are of Han Chinese, Thai, Korean or Japanese descent, talk to your doctor or pharmacist before starting treatment.[1]  

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

What is the typical dosage of allopurinol?

The typical initial adult dose of allopurinol to treat gout is around 100mg, taken once daily. This dose may be increased gradually up to a maximum of 900mg per day in divided doses, based on blood uric acid levels[1].  

In other cases, the dose is based on factors like comorbidities, condition, age, and weight. Always follow your doctor’s or pharmacist’s instructions for best results[1].  

How do you take allopurinol?

Allopurinol is normally taken once a day, preferably after a meal to reduce stomach upset. It’s a good idea to drink plenty of fluids alongside allopurinol to help prevent kidney stones and keep taking it regularly, even if you feel well. It is important to keep taking allopurinol can take several weeks to feel the full benefit of gout prevention and a reduction of urate levels[1]. 

Can you stop taking allopurinol suddenly?

You should not stop taking your regular dose of allopurinol suddenly unless told to by your doctor or pharmacist. Stopping can cause your urate levels to rise. This can then increase the risk of another gout attack[1]. 

What should you do if you take too much allopurinol?

The symptoms of allopurinol overdose can include nausea, vomiting, dizziness, or diarrhoea. Get emergency medical attention if you take too much, even if you feel well at the time[1]. 

What should you do if you forget a dose of allopurinol?

If you miss a dose of allopurinol, you can take it as soon as you remember. If it’s time for your next dose, then just take that one and carry on. Do not double up to make up for a missed dose. Taking your dose at the same time each day can help stick to your schedule[1]. 

Which medicines should you avoid while taking allopurinol?

Some medicines may interact with allopurinol. Tell your doctor or pharmacist about all medicines, including any supplements, that you’re taking to avoid any unwanted side effects. The most notable medicines that should be avoided with allopurinol include[1]:  

• Azathioprine or mercaptopurine, increases the risk of haematological toxicity 

• Diuretics (like furosemide, bendroflumethiazide and indapamide) that may increase risk of hypersensitivity reactions  

• ACE inhibitors (like ramipril) can increase the risk of hypersensitivity and haematological reactions 

• Warfarin, as allopurinol can increase its blood-thinning effect 

• Ampicillin/amoxicillin which may increase risk of rash 

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].

What are the side effects of allopurinol?

Allopurinol’s most common side effects are mild skin rashes, nausea, vomiting and diarrhoea. Other serious (but rare) side effects are[1]: 

• Severe allergic reactions like rash, peeling skin, fever, mouth ulcers (these may indicate Stevens-Johnson syndrome) 

• Liver problems 

• Blood disorders (such as unusual bruising or infections) 

Always contact a healthcare provider if you're unsure about any symptoms. If any side effects are worrying, severe, or persistent, contact your doctor.

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]. 

Frequently asked questions about allopurinol

Can I drink alcohol while taking allopurinol? 

Yes, you can drink alcohol while taking allopurinol. But it’s best to do so in moderation. Excess alcohol, especially beer, can raise uric acid levels and trigger gout attacks[1]. 

Will I need to take allopurinol for life? 

You may need to take allopurinol in the long term. If you have chronic gout or frequent attacks, your doctor or pharmacist may advise you take it for life to prevent further incidents[1]. 

Can I take painkillers with allopurinol? 

Yes, you can use NSAIDs (like ibuprofen) or colchicine to relieve acute gout attacks. Check with your doctor or pharmacist to ensure safe combinations and dosages[1]. 

Does allopurinol treat a current gout attack? 

Allopurinol lowers uric acid levels to prevent future attacks – but does not relieve active symptoms[1].

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