Allopurinol

WARNING/CAUTION: Even though it may be rare, some people may have very bad and sometimes deadly side effects when taking a drug. Tell your doctor or get medical help right away if you have any of the following signs or symptoms that may be related to a very bad side effect:Signs of an allergic reaction, like rash; hives; itching; red, swollen, blistered, or peeling skin with or without fever; wheezing; tightness in the chest or throat; trouble breathing, swallowing, or talking; unusual hoarseness; or swelling of the mouth, face, lips, tongue, or throat.Signs of kidney problems like unable to pass urine, change in how much urine is passed, blood in the urine, or a big weight gain.Pain when passing urine.Back pain, belly pain, or blood in the urine. May be signs of a kidney stone.Eye irritation.Change in eyesight.Joint pain that is new or worse.Swollen gland.Shortness of breath, a big weight gain, or swelling in the arms or legs.Chest pain or pressure.Liver problems have happened with this drug. Sometimes, liver problems have not gone back to normal after this drug was stopped. Call your doctor right away if you have signs of liver problems like dark urine, feeling tired, not hungry, upset stomach or stomach pain, light-colored stools, throwing up, or yellow skin or eyes.A very bad skin reaction (Stevens-Johnson syndrome/toxic epidermal necrolysis) may happen. It can cause very bad health problems that may not go away, and sometimes death. Get medical help right away if you have signs like red, swollen, blistered, or peeling skin (with or without fever); red or irritated eyes; or sores in your mouth, throat, nose, or eyes.Low blood cell counts have happened with this drug. Most of the time, this happened in people who were also taking other drugs that can cause low blood cell counts. Call your doctor right away if you have any signs of infection like fever, chills, or sore throat; any unexplained bruising or bleeding; or you feel very tired or weak.