Allopurinol: A XANTHINE OXIDASE inhibitor that decreases URIC ACID production. It also acts as an antimetabolite on some simpler organisms.Gout Suppressants: Agents that increase uric acid excretion by the kidney (URICOSURIC AGENTS), decrease uric acid production (antihyperuricemics), or alleviate the pain and inflammation of acute attacks of gout.Xanthine Oxidase: An iron-molybdenum flavoprotein containing FLAVIN-ADENINE DINUCLEOTIDE that oxidizes hypoxanthine, some other purines and pterins, and aldehydes. Deficiency of the enzyme, an autosomal recessive trait, causes xanthinuria.Oxypurinol: A xanthine oxidase inhibitor.Gout: Hereditary metabolic disorder characterized by recurrent acute arthritis, hyperuricemia and deposition of sodium urate in and around the joints, sometimes with formation of uric acid calculi.Uric Acid: An oxidation product, via XANTHINE OXIDASE, of oxypurines such as XANTHINE and HYPOXANTHINE. It is the final oxidation product of purine catabolism in humans and primates, whereas in most other mammals URATE OXIDASE further oxidizes it to ALLANTOIN.Hyperuricemia: Excessive URIC ACID or urate in blood as defined by its solubility in plasma at 37 degrees C; greater than 0.42mmol per liter (7.0mg/dL) in men or 0.36mmol per liter (6.0mg/dL) in women. This condition is caused by overproduction of uric acid or impaired renal clearance. Hyperuricemia can be acquired, drug-induced or genetically determined (LESCH-NYHAN SYNDROME). It is associated with HYPERTENSION and GOUT.Uricosuric Agents: Gout suppressants that act directly on the renal tubule to increase the excretion of uric acid, thus reducing its concentrations in plasma.Tumor Lysis Syndrome: A syndrome resulting from cytotoxic therapy, occurring generally in aggressive, rapidly proliferating lymphoproliferative disorders. It is characterized by combinations of hyperuricemia, lactic acidosis, hyperkalemia, hyperphosphatemia and hypocalcemia.Antimetabolites: Drugs that are chemically similar to naturally occurring metabolites, but differ enough to interfere with normal metabolic pathways. (From AMA Drug Evaluations Annual, 1994, p2033)Urate Oxidase: An enzyme that catalyzes the conversion of urate and unidentified products. It is a copper protein. The initial products decompose to form allantoin. EC 1.7.3.3.Hypoxanthines: Purine bases related to hypoxanthine, an intermediate product of uric acid synthesis and a breakdown product of adenine catabolism.Xanthine: A purine base found in most body tissues and fluids, certain plants, and some urinary calculi. It is an intermediate in the degradation of adenosine monophosphate to uric acid, being formed by oxidation of hypoxanthine. The methylated xanthine compounds caffeine, theobromine, and theophylline and their derivatives are used in medicine for their bronchodilator effects. (Dorland, 28th ed)Free Radical Scavengers: Substances that influence the course of a chemical reaction by ready combination with free radicals. Among other effects, this combining activity protects pancreatic islets against damage by cytokines and prevents myocardial and pulmonary perfusion injuries.Xanthines: Purine bases found in body tissues and fluids and in some plants.Benzbromarone: Uricosuric that acts by increasing uric acid clearance. It is used in the treatment of gout.Xanthine Dehydrogenase: An enzyme that catalyzes the oxidation of XANTHINE in the presence of NAD+ to form URIC ACID and NADH. It acts also on a variety of other purines and aldehydes.Hypoxanthine: A purine and a reaction intermediate in the metabolism of adenosine and in the formation of nucleic acids by the salvage pathway.Drug Hypersensitivity: Immunologically mediated adverse reactions to medicinal substances used legally or illegally.Drug Eruptions: Adverse cutaneous reactions caused by ingestion, parenteral use, or local application of a drug. These may assume various morphologic patterns and produce various types of lesions.Enzyme Inhibitors: Compounds or agents that combine with an enzyme in such a manner as to prevent the normal substrate-enzyme combination and the catalytic reaction.Antiprotozoal Agents: Substances that are destructive to protozoans.Probenecid: The prototypical uricosuric agent. It inhibits the renal excretion of organic anions and reduces tubular reabsorption of urate. Probenecid has also been used to treat patients with renal impairment, and, because it reduces the renal tubular excretion of other drugs, has been used as an adjunct to antibacterial therapy.Stevens-Johnson Syndrome: Rare cutaneous eruption characterized by extensive KERATINOCYTE apoptosis resulting in skin detachment with mucosal involvement. It is often provoked by the use of drugs (e.g., antibiotics and anticonvulsants) or associated with PNEUMONIA, MYCOPLASMA. It is considered a continuum of Toxic Epidermal Necrolysis.