Allopurinol

What is Allopurinol?

Allopurinol is a prescription-only medication that lowers uric acid levels in the blood to prevent conditions, such as gout, kidney stones, and high uric acid levels during cancer treatment. It is a xanthine oxidase inhibitor because it blocks xanthine oxidase, the enzyme responsible for uric acid production in the body.

Allopurinol is available as an oral tablet and is usually taken once daily, preferably with food and water. It was discovered in the early 1960s by Dr Gertrude Elion and Dr George Hitchings. Their pioneering work on this and other medications that improve metabolism eventually earned them a Nobel Prize.

What is Allopurinol Used For?

Allopurinol is usually used to relieve the symptoms of gout, a form of arthritis that is caused by the crystallisation of uric acid in the joints. However, it can also be used to treat other conditions caused by high uric acid levels, including kidney stones.

At Prescription Doctor, our clinicians can only prescribe allopurinol for gout, a painful type of inflammatory arthritis that commonly affects the big toe. The symptoms of gout include:

• Sudden, severe pain or tenderness in the joint, particularly at night
• Swelling, redness, and skin discolouration around the joint
• Extreme sensitivity around the joint; even a bedsheet touching it can feel unbearable

Allopurinol does not treat the sudden, sharp pain associated with gout flare-ups, but it can lower uric acid levels in your blood to help prevent them from occurring.

What Does Allopurinol Do?

Allopurinol blocks the enzyme xanthine oxidase, which plays an important role in uric acid production. This reduces uric acid (the compound responsible for painful gout attacks) production, thereby lowering uric acid levels and reducing the likelihood of gout attacks.

Reducing uric acid levels in the body also helps reduce joint inflammation, which can lead to reduced pain and swelling. Plus, allopurinol works as a prophylactic, preventing the formation of new uric acid crystals and minimising the risk of future gout flare-ups.

How Long Does Allopurinol Take to Work?

Uric acid levels usually begin to fall within 1 to 2 weeks of starting allopurinol, but it can take several weeks or even months to take effect fully. The timeframe will vary from person to person due to factors such as gout severity, overall health, and adherence to prescriptions.

How Effective is Allopurinol for Gout?

Research suggests that while allopurinol does not reduce the number of gout attacks, it does increase the number of people who reach target uric acid levels within 30 days. 96% of people achieved the target serum uric acid levels while taking allopurinol daily. The same paper found that 4% fewer people had an acute gout attack while taking allopurinol.

Some studies suggest that allopurinol helps 42% of patients with gout reduce their uric acid levels to ≤6 mg/dL, the recommended blood uric acid target. If you’re unsure about your uric acid levels, you can purchase a test kit from Prescription Doctor.

How to Take Allopurinol Tablets

Allopurinol tablets should be taken after food and swallowed whole with a glass of water. You mustn’t chew the allopurinol tablet, but there is a break line on the pill to help you break the tablet if you have difficulty swallowing it whole. It’s essential that you always take the medication exactly as your prescriber advises and check with them if you are ever unsure.

Allopurinol Dosage Information

The recommended allopurinol dosage for gout ranges from 100mg to 900mg each day. You will typically start on a low dose to reduce the risk of side effects, which will be increased if necessary. Regular monitoring is required to ensure you are on the right strength for your circumstances.

If you are an older person, or have reduced liver or kidney function, your doctor may prescribe a lower dose or to take it at longer intervals. If you have dialysis two or three times a week, your doctor may prescribe a dose of 300 or 400 mg, which needs to be taken straight after your dialysis.

If You Forget to Take Allopurinol

Take your missed dose of allopurinol as soon as you remember, unless it is nearly time for your next one. In this case, just skip the missed dose and take your next one at the usual time. Do not take a double dose to make up for one you have missed.

If You Take Too Many Allopurinol Tablets

If you take more allopurinol than you should, seek medical attention or go straight to your nearest hospital. Ensure that you take the medicine pack with you so it can be determined what tablets you have taken and how many. Possible signs of an overdose include diarrhoea, dizziness, nausea, and vomiting.

Side Effects and Cautions

Just like all medications, allopurinol can cause side effects in some people, so it is important to understand what they are alongside any potential cautions. This will give you a better idea of what to look out for and when you may need to seek medical advice.

Possible Side Effects of Allopurinol

Allopurinol can cause side effects, but not everyone will get them. For most people, the side effects are mild and temporary, improving as your body gets used to the medication.

Please note that the above is not a complete list of possible allopurinol side effects. More information can be found within the Patient Information Leaflet that comes with the medication. If you get any allopurinol side effects, including any that aren’t listed here, you can report them to the Yellow Card Scheme to give clinicians a better understanding of the safety of this medication.

Allopurinol and Hypersensitivity

Allergic or hypersensitivity reactions are uncommon but possible. If you get any of the following hypersensitivity reactions while taking allopurinol, stop taking it immediately and see a doctor, or in an emergency go to A&E:

Allopurinol Warnings and Interactions

Although Allopurinol is effective for gout, it may not be suitable for everyone. You should not take the medication if you are allergic to allopurinol or any other ingredients in the treatment. If you are unsure, speak to your clinician or doctor beforehand.

Precautions Before Taking Allopurinol

Before taking allopurinol, tell the clinician if you:

• Are of Han Chinese, African, or Indian origin
• Have problems with your liver or kidneys
• Have heart problems or high blood pressure and take diuretics or a medication called an ACE-inhibitor
• Are currently having a gout attack
• Have thyroid problems

You should take special care with allopurinol if you have:

• Serious skin rashes (hypersensitivity syndrome, Stevens-Johnson syndrome, toxic epidermal necrolysis)
• Cancer or Lesch-Nyhan syndrome
• Kidney stones

Allopurinol and Other Medicines

Before taking allopurinol, it is important that you tell the clinician about any prescribed, over-the-counter, or herbal medicines you are taking. That’s because some medicines can affect how allopurinol works, and vice versa.

Tell the clinician if you are taking any of the following:

• aspirin
• theophylline, used for breathing problems
• medicines used for fits (epilepsy), phenytoin
• vidarabine, used to treat herpes or chickenpox
• antibiotics (ampicillin or amoxicillin)
• didanosine, used to treat HIV infection
• medicines used for cancer
• medicines used to reduce your immune response (immunosuppressants)
• medicines used to treat diabetes
• medicines for heart problems or high blood pressure such as ACE inhibitors or water tablets (diuretics)
• medicines used to thin your blood (anticoagulants), such as warfarin
• any other medicine to treat gout
• 6-Mercaptopurine (used to treat blood cancer)
• Azathioprine (used to suppress the immune system)

You should leave at least 3 hours between taking allopurinol and aluminium hydroxide, as taking them together can reduce their effectiveness.

If you take allopurinol with cytostatics, such as cyclophosphamide, doxorubicin, bleomycin, procarbazine, alkyl halogenides, blood disorders can happen more frequently than when they are taken alone. You may need regular blood tests to check your blood health.

Pregnancy and Breastfeeding

Before taking allopurinol, tell the clinician if you are pregnant, think you might be pregnant, or are breastfeeding. It is not recommended that you take allopurinol while breastfeeding as the medicine can be excreted in your breast milk.

Where Can I Buy Allopurinol Tablets in the UK?

Allopurinol is a prescription-only medicine, which means you must have the approval of a qualified clinician, doctor, or pharmacist to get it for gout. It may be available on the NHS or via a private prescription from an online pharmacy service, depending on your preference.

Can You Buy Allopurinol Over the Counter?

No, allopurinol is not available over the counter; you must have a prescription from a clinician to get it. They must check that allopurinol is both safe and suitable for you to take.

Is Allopurinol Available on the NHS?

Yes, allopurinol is available on the NHS to treat gout. Your GP can prescribe allopurinol as a long-term gout treatment once they have assessed your symptoms and diagnosed gout. If you pay for your prescriptions, allopurinol will be subject to the current NHS prescription charge.

Can I Buy Allopurinol Online?

Yes, allopurinol is available online from regulated services like Prescription Doctor. You will need to fill out a short online health questionnaire for our clinician to review. This enables them to ensure that allopurinol is a suitable medication for you.

If it is, we will post your medication in discreet packaging to maintain your confidentiality. If your order is approved before 3pm Monday to Friday, we will dispatch your medication for next-day delivery.

Frequently Asked Questions About Allopurinol Tablets