The prescription medication allopurinol prevents users' bodies from producing excess uric acid. This action of allopurinol helps prevent gout attacks, prevent the formation of kidney stones containing calcium oxalate and avoid spikes in blood concentrations of urea that can occur when chemotherapy drug destroy leukaemia or lymphoma cancer cells. Allopurinol use has resulted in fatal allergic reactions and gout attacks. Common side effects from taking allopurinol include nausea and diarrhoea.
An all-caps warning in the prescribing information for allopurinol states, "ZYLOPRIM SHOULD BE DISCONTINUED AT THE FIRST APPEARANCE OF SKIN RASH OR OTHER SIGNS WHICH MAY INDICATE AN ALLERGIC REACTION." Elsewhere, in the prescribing information, rash is identified as one of the more common side effects from taking allopurinol. Signs of an allergy to allopurinol other than rash include itching, chills, sore throat and swelling of the lips or mouth.
Other Warnings and Precautions
Patients taking allopurinol should not drive or engage in other potentially dangerous activities until they know whether the medication will make them sleepy. Also, patients may need to have doses of other gout or kidney stone medications lowered when they take allopurinol. Last, to ensure the medication works optimally, patients should drink at least eight glasses of water each day.
Common Side Effects
Acute gout attacks have been the most common side effect from allopurinol use, despite the medication's use to prevent gout. A note in the prescribing information for allopurinol suggests that worsening of gout occurs most frequently when patients take more than 800 mg maximum recommended daily dose of the medication. Patients also have experienced diarrhoea, nausea, increases in blood concentrations of phosphates and increases in enzymes that can indicate liver damage.
Rarer Side Effects
Fewer than one per cent of patients taking allopurinol have experienced dark patches on their skin (i.e., ecchymosis), swollen veins, fevers, headaches, liver damage, artery death (i.e., necrotizing angiitis), decreased red and white blood cell counts, muscle and joint pain, somnolence, kidney failure, changes in taste sensation and pins and needles" (i.e., parethesia).
Three companies produced brand-name versions of allopurinol for the U.S. market. These branded are Aloprim from Bioniche Pharmaceuticals, Lopurin from Dr. Reddy's Laboratories and Zyloprim from Promethesus Laboratories. The drug makers Apotex, Caraco, Mylan, Mutual, Northstar Laboratories, Vintage and Watson produce generic versions of allopurinol.