Allopurinol is used to prevent or lower high uric acid levels in the blood. It is also used to prevent or lower excess uric acid levels caused by cancer medicines or in patients with kidney stones. A high uric acid level can cause gout or gouty arthritis (joint pain and inflammation). Allopurinol is a xanthine oxidase inhibitor that works by decreasing the uric acid produced by the body.

This medicine is available only with your doctor's prescription.

Take this medicine exactly as directed by your doctor. Do not take more of it, do not take it more often, and do not take it for a longer time than your doctor ordered. To do so may increase the chance of side effects.

You may take this medicine after meals to avoid stomach upset.

Take this medicine with plenty of liquids to help prevent kidney stones. Check with your doctor about the amount of liquid you should drink each day. You should also increase your fiber intake.

You may need to lessen your intake of animal protein, sodium, refined sugars, or foods rich in oxalate and calcium, especially if you have kidney stones that keep coming back.

Along with its needed effects, a medicine may cause some unwanted effects. Although not all of these side effects may occur, if they do occur they may need medical attention.

Check with your doctor immediately if any of the following side effects occur:

More common

Ankle, knee, or great toe joint pain

joint stiffness or swelling

rash

rash with flat lesions or small raised lesions on the skin

Rare

Agitation

ammonia-like breath odor

anxiety

bleeding gums

blistering, peeling, or loosening of the skin

blood in the urine or stools

bloody nose

bloody or black, tarry stools

blue or pale skin

bruising

changes in skin color

chest pain or discomfort

chest pain, possibly moving to the left arm, neck, or shoulder

chills

clay-colored stools

cloudy urine

confusion

constipation

cough

coughing up blood

cracks in the skin

dark urine

decreased awareness or responsiveness

decreased urine output

depression

diarrhea

difficulty with breathing

dizziness

drowsiness

dry mouth

feeling of warmth or heat

fever

flushing or redness of the skin, especially on the face and neck

general feeling of discomfort or illness

headache

hives or welts, itching, skin rash

hoarseness

hostility

incoherent speech

increased urination

irritability

joint or muscle pain

large, flat, blue or purplish patches in the skin

light-colored stools

loss of appetite

loss of consciousness

loss of heat from the body

lower back or side pain

metallic taste

muscle twitching

muscle weakness

nausea

noisy breathing

pain, tenderness, or swelling of the foot or leg

painful or difficult urination

pinpoint red or purple spots on the skin

rapid weight gain

red, irritated eyes

red, swollen skin

redness, soreness, or itching skin

right upper abdominal or stomach pain and fullness

scaly skin

seizures

severe sleepiness

severe stomach pain

slow or irregular heartbeat

sore throat

sores, ulcers, or white spots on the lips or in the mouth

sores, welting, or blisters

stomach pain

sweating

swelling of the face, ankles, hands, or lower legs

swollen or painful glands

swollen, painful, or tender lymph glands in the neck, armpit, or groin

thirst

tightness in the chest

unpleasant breath odor

unusual bleeding or bruising

unusual drowsiness, dullness, tiredness, weakness, or feeling of sluggishness

unusual weight gain or loss

vomiting

vomiting of blood or material that looks like coffee grounds

yellow eyes or skin

Some side effects may occur that usually do not need medical attention. These side effects may go away during treatment as your body adjusts to the medicine. Also, your health care professional may be able to tell you about ways to prevent or reduce some of these side effects. Check with your health care professional if any of the following side effects continue or are bothersome or if you have any questions about them:

Rare

Bad, unusual, or unpleasant (after) taste

blindness

blue-yellow color blindness

blurred vision

body aches or pain

burning feeling in the chest or stomach

burning, crawling, itching, numbness, prickling, "pins and needles", or tingling feelings

burning, dry, or itching eyes

change in taste

change in vision

congestion

continuing ringing or buzzing or other unexplained noise in the ears

decreased interest in sexual intercourse

decreased vision

difficulty with moving

discharge or excessive tearing

feeling of constant movement of self or surroundings

hair loss or thinning of the hair

hearing loss

impaired vision

inability to have or keep an erection

indigestion

lack or loss of strength

loss in sexual ability, desire, drive, or performance

loss of appetite

loss of memory

multiple swollen and inflamed skin lesions

muscle pain, cramps, or stiffness

muscular pain, tenderness, wasting, or weakness

problems with memory

redness, pain, or swelling of the eye, eyelid, or inner lining of the eyelid

runny nose

sensation of spinning

sensitivity to light

sleepiness or unusual drowsiness

sleeplessness

sneezing

stomach upset

stuffy nose

sweating

swelling of the breasts or breast soreness in both females and males

swelling of the salivary glands

swelling or inflammation of the mouth

tearing

tender, swollen glands in the neck

tenderness in the stomach area

throbbing pain

trouble getting pregnant

trouble with sleeping

trouble with swallowing

unsteadiness or awkwardness

voice changes

weakness in the arms, hands, legs, or feet

weight loss

Other side effects not listed may also occur in some patients. If you notice any other effects, check with your healthcare professional.

Call your doctor for medical advice about side effects. You may report side effects to the FDA at 1-800-FDA-1088.

It is very important that your doctor check your or your child's progress at regular visits to make sure that this medicine is working properly. Blood and urine tests may be needed to check for unwanted effects.

When you start using this medicine, you may have more gout attacks. Keep using the medicine even if this happens. Your doctor may give you other medicines (eg, colchicine, pain medicines [NSAIDs]) to help prevent the gout attacks.

Serious skin reactions can occur with this medicine. Call your doctor right away at the first appearance of a skin rash or allergic reaction (eg, trouble breathing or swallowing, swelling of your hands, face, or mouth). Check with your doctor if you also develop blistering, peeling, or loosening of the skin, red skin lesions, severe acne, or sores or ulcers on the skin.

Check with your doctor right away if you or your child have stomach pain or tenderness, pale stools, dark urine, loss of appetite, nausea, unusual tiredness or weakness, or yellow eyes or skin. These could be symptoms of a serious liver problem.

This medicine may cause some people to become drowsy or less alert than they are normally. Do not drive or do anything else that could be dangerous until you know how this medicine affects you.

Do not take other medicines unless they have been discussed with your doctor. This includes prescription or nonprescription (over-the-counter [OTC]) medicines and herbal or vitamin supplements.