How Long Does Allopurinol Take to Work? Answers to 5 Common Allopurinol FAQs

What’s the first thing you think of when you hear the word “gout”? Benjamin Franklin, beer, or red meat might come to mind. Gout is a painful joint inflammation caused by a buildup of sharp uric acid crystals that collect in the joints.

Franklin did indeed have gout during his lifetime — he even wrote a funny story about the condition that bothered him so much. What he didn’t have was a way to treat his gout. But fast-forward to now, there are many ways to manage it.

Allopurinol (Zyloprim, Aloprim) is one oral medication used to lower the amount of uric acid that your body makes. This makes it a helpful gout treatment. But gout isn’t the only condition that’s caused by too much uric acid. Excess uric acid can also cause kidney stones. And if you’re receiving certain cancer treatments, high uric acid could be a sign of tumor lysis syndrome (TLS) — a serious condition that happens when a large amount of cancer cells die quickly and release their contents into your blood.

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Allopurinol can prevent each of these health conditions. But it’s important to understand details about how this medication works so you can get the most out of it.

1. How long does allopurinol take to work?

Allopurinol doesn’t start working right away. This is because allopurinol prevents your body from making more uric acid. It can’t remove the uric acid that’s already there.

Allopurinol does this by blocking a protein called xanthine oxidase. This protein normally plays a role in uric acid production; interfering with it gives your body time to start breaking down high levels of uric acid that are already there.

Gout

Your uric acid levels should start to decrease after 1 to 2 weeks of taking allopurinol. Your primary care specialist will likely start you at a low dose and slowly increase it over time.

This dose-escalation process can take several months, though. This slow increase helps lower the risk of gout flares, which can happen when you first start taking allopurinol. Gout flares happen as allopurinol allows your body to break down uric acid crystals. These crystals can find their way into your joints and cause inflammation.

Tumor lysis syndrome (TLS)

TLS is a serious medical condition that happens when cancer treatments quickly break down cancer cells. As a result, cancer cells spill their contents — including uric acid — into the blood.

EXPERT PICKS: WHAT TO READ NEXT

• Can’t take allopurinol? Learn if an alternative xanthine oxidase inhibitor might be better for you.

• Allopurinol side effects deep dive: Gain a deeper understanding of side effects you could encounter while taking allopurinol.

• Let your diet help you: Learn which foods are high in purines and could contribute to a possible gout flare-up.

Your kidneys are normally able to get rid of uric acid. But when uric acid levels rise too quickly, it can overwhelm your kidneys and cause damage. Since allopurinol takes some time to work, it’s best to use it as a prevention and start taking it 1 to 2 days before your cancer treatment.

Keep in mind: Not all cancer treatments cause TLS. Your oncologist will let you know if you need to take allopurinol to prevent TLS.

Kidney stones

Allopurinol is mostly used to prevent kidney stones caused by high uric acid and calcium levels. But it doesn’t actively treat them. If you have a kidney stone, allopurinol can prevent it from getting bigger. This allows you a chance to pass it.

How long it takes to pass the kidney stone depends more on its size and less on how quickly allopurinol works.

2. How long does it take to see full effects from allopurinol?

This, again, depends on why you’re taking allopurinol. Allopurinol can be helpful in preventing TLS after just a few days of taking it, while it takes much longer to see improvement for gout.

Gout

It can take anywhere from 6 to 12 months for gout symptoms to fully disappear after starting allopurinol. This may be related to the need to slowly increase the dose.

If you’re still having gout flares after a year of taking allopurinol, check in with your primary care team or rheumatologist to make sure your dose is high enough.

Tumor lysis syndrome

It’s usually OK to stop taking allopurinol once your uric acid levels are normal following your cancer treatment. This typically happens after about 7 days.

Kidney stones

Since allopurinol is used for prevention, there isn’t necessarily a specific timeline to see its full effects for kidney stones. If allopurinol isn’t preventing you from developing new kidney stones, it’s time to discuss alternatives with your primary care team or nephrologist.

3. Are there factors that affect how long allopurinol takes to work?

Yes. Effective gout treatment depends on whether you can get your uric acid levels to a normal level. This timing can be affected by multiple factors, including:

• Your dose: Although it’s recommended to start at a 100 mg daily dosage for gout, your primary care team or rheumatologist may raise your dose to as high as 800 mg daily. It takes longer to slowly increase to higher doses.

• Your dose increase (titration) schedule: Some healthcare professionals may feel comfortable increasing your dose as often as weekly. Others may titrate every 2 to 5 weeks. This depends on their medical judgement, as well as any other conditions you have.

• Gout severity: Most people with mild cases of gout can effectively treat it with 200 mg to 300 mg of allopurinol daily. More severe cases of gout often require higher allopurinol dosages of 400 mg to 600 mg daily, which take longer to reach.

• Kidney function: Your kidneys remove allopurinol from the body. If you have decreased kidney function, you’ll need a lower starting dose of allopurinol.

• Drug interactions: Certain medication classes, such as angiotensin-converting enzyme (ACE) inhibitors, thiazide diuretics, and penicillin antibiotics, can increase the risk of having an allergic reaction to allopurinol. In this case, you’d likely need to stop taking allopurinol and switch to an alternative treatment.

4. What should you expect when starting allopurinol?

If you’re taking allopurinol for gout, you’ll likely need to take additional medications — such as colchicine (Colcrys); nonsteroidal anti-inflammatory drugs (NSAIDs), such as ibuprofen (Advil, Motrin); or prednisone — for the first 3 to 6 months of taking it. Combining medications such as these with allopurinol is necessary to treat and prevent gout flares. Even if you get a gout flare while taking allopurinol, it’s important that you continue taking it.

You’ll also need regular blood draws while taking allopurinol. How often you need them depends on why you’re taking it. For instance, your oncologist will likely draw your blood daily if you’re taking allopurinol to prevent TLS. For gout, your healthcare professional will likely draw your blood with every dose increase to make sure you’re making progress toward your uric acid goals. They’ll also monitor your kidney and liver function to ensure that allopurinol isn’t aggravating them. After you hit your target dose, you’ll likely only need lab draws every 6 months.

There are some dietary precautions to take, too. You should try to stay well hydrated by drinking at least 2 L (8 to 9 cups) of water every day. This helps flush uric acid out of your body and prevent kidney stones. Taking allopurinol with food can also prevent nausea.

Does allopurinol shorten your life?

No. A meta-analysis combining the results of four studies found that allopurinol does not increase the risk of death in people with gout.

5. How long do you need to take allopurinol?

If you’re taking allopurinol to prevent gout flares and kidney stones, you’ll likely need to take it chronically (long-term) — potentially for the rest of your life. If you’re taking it for TLS, you shouldn’t need to take it for longer than a week.

Always check in with your healthcare professional prior to stopping allopurinol. Abruptly stopping it could cause a gout flare, another kidney stone, or TLS.

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Written by:

Rachel Feaster, PharmD, BCOP, BCPS

Rachel Feaster has over 10 years of professional experience in ambulatory, inpatient, pharmacogenomics, and oncology care. She is board certified in oncology and pharmacotherapy.

Edited by:

Joshua Murdock, PharmD, BCBBS

Joshua Murdock, PharmD, BCBBS, is a licensed pharmacist in Arizona, Colorado, and Rhode Island. He has worked in the pharmacy industry for more than 10 years and currently serves as a pharmacy editor for GoodRx.

Reviewed by:

Christina Aungst, PharmD

Christina Aungst, PharmD, is a pharmacy editor for GoodRx. She began writing for GoodRx Health in 2019, transitioning from freelance writer to editor in 2021.

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