Allopurinol prevention

These patients have a high level of urate because of the breakdown of nucleic acids. Allopurinol prevents the formation of kidney stones and blocks other deleterious consequences of hyperuricemia by preventing the formation of urate (Section 25.6.1). 

Allopurinol is indicated in recurrent gout, when at least three attacks occur per year, in blood diseases where there is spontaneous hyperuiicaemia, and during treatment of myeloproliferative disorders where cell destruction creates a high urate load. Allopurinol prevents the hyperuricaemia due to diuretics and may be combined with a uricosuric agent. The dose is usually 300 mg/d by mouth but some patients may need as much as 600 mg daily. 

Allopurinol prevents the oxidation of mercap-topurine to an inactive metabolite if an ordinary dose of mercaptopurine is given to a patient whose gout is being treated with allopurinol, dangerous potentiation occurs (see also azathiopurine, p. 292). 

Alemtuzumab - monoclonal antibody leukaemia treatment Allopurinol - prevention of uric acid production, gout treatment Alteplase - fibrinolytic thrombosis Amantadine - antiviral Parkinson s disease Amfetamine (amphetamine) - CNS stimulant (little therapeutic use)... 

Ischemia may cause deterioration of myocardial function through excessive loss of ATP and the myocardial pool of purine nucleosides. The enzyme, xanthine oxidase, irreversibly converts purines to uric acid. After periods of asphyxia, an infusion of adenosine caused a markedly accelerated restoration of normal myocardial nucleotides. in coronary-ligated dogs and sheep, the xanthine oxidase inhibitor allopurinol prevented or reversed nucleotide loss from the myocardium, ST-depression and cardiac arrhythmias due to myocardial ischemia. 

Allopurinol, which inhibits XO and scavenges superoxide, prevents the increase in free-radical production... 

Studies of both acute and chronic pancreatitis in humans and in animals support the hypothesis that free radicals are involved in the pathogenesis of pancreatitis. There is some conflicting data from the animal work, which may in part be due to differences in the models used. It does also indicate that free radicals are not the only factors involved and su ests that activation of pancreatic enzymes are also imprortant, particularly in the development of haemorrhagic pancreatitis (Sanfey, 1991). The findings of decreased antioxidant defences and the success of treatment reported in chronic pancreatitis with a cocktail of antioxidants and with allopurinol surest further studies are required to establish the role of antioxidants in pancreatic disease and its prevention. 

Paracetamol-induced hepatotoxicity can be prevented in animals with SOD, catalase and allopurinol (Kyle et al., 1987 Jaeschke, 1990 Tirmenstein and Nelson, 1990), and by N-acetyl-L-cysteine or methionine in humans (Meredith et al., 1986 Nelson, 1990). The protective efiect of allopurinol in mice only occurred at high concentrations, suggesting that its effect was related to scavenging of ROMs rather than inhibition of their production by XO (Jaeschke, 1990). 

RH is admitted to the pediatric oncology service. She is started on allopurinol and intravenous fluids with sodium bicarbonate to prevent tumor lysis syndrome. According to her risk status, she will receive a three-drug induction with vincristine, dexamethasone, and pegylated asparaginase. She also will receive intrathecal (IT) chemotherapy for CNS prophylaxis with methotrexate, cytarabine, and hydrocortisone. 

Pharmacologic prevention strategies for tumor lysis syndrome are aimed at low- and high-risk patients (Fig. 96-7). Allopurinol is a xanthine oxidase inhibitor that is used for prevention only because it has no effect on preexisting elevated uric acid. Rasburicase is a recombinant form of urate oxidase that is useful for both prevention and treatment but is extremely expensive (Table 96-12). Although the approved dose is 0.2 mg/kg per day... 

Unlabeled uses In a limited number of patients, the use of an allopurinol mouthwash (20 mg in 3% methylcellulose 1 mg/mL) after fluorouracil administration prevented stomatitis, a major dose-limiting toxicity of fluorouracil. However, another report indicated that allopurinol mouthwash is not effective. Further study is needed. 

Allopurinol is an xanthine oxidase inhibitor. It reduces urate production and is used in primary and secondary urate overproduction. Therapy of hyperuricemia prevents recurring attacks of acute gouty arthritis. Allopurinol dosages are 300 mg/day for serum creatinine < 1.5 mg/dl and 100 mg/day for serum creatinine between 1.6-2.0 mg/dl. Reduction of tophi is slow with allopurinol, particularly in patients with giant tophi and renal insufficiency where drug dosage is limited. 

Busulfan is used in the palliative treatment of chronic granulocytic leukemia. Daily oral therapy results in decreased peripheral white blood cells and improved symptoms in almost all patients during the chronic phase of the disease. Excessive uric acid production from rapid tumor cell lysis should be prevented by coadministration of allopurinol. 

As noted above, colchicine or an NSAID should be given during the first weeks of allopurinol therapy to prevent the gouty arthritis episodes that sometimes occur. 

MP is converted to an inactive metabolite (6-thiouric acid) by an oxidation reaction catalyzed by xanthine oxidase, whereas 6-TG undergoes deamination. This is an important issue because the purine analog allopurinol, a potent xanthine oxidase inhibitor, is frequently used as a supportive care measure in the treatment of acute leukemias to prevent the development of hyperuricemia that often occurs with tumor cell lysis. Because allopurinol inhibits xanthine oxidase, simultaneous therapy with allopurinol and 6-MP would result in increased levels of 6-MP, thereby leading to excessive toxicity. In this setting, the dose of mercaptopurine must be reduced by 50-75%. In contrast, such an interaction does not occur with 6-TG, which can be used in full doses with allopurinol. 

Azathioprine is well absorbed from the gastrointestinal tract and is metabolized primarily to mercaptopurine. Xanthine oxidase splits much of the active material to 6-thiouric acid prior to excretion in the urine. After administration of azathioprine, small amounts of unchanged drug and mercaptopurine are also excreted by the kidney, and as much as a twofold increase in toxicity may occur in anephric or anuric patients. Since much of the drug s inactivation depends on xanthine oxidase, patients who are also receiving allopurinol (see Chapters 36 and 54) for control of hyperuricemia should have the dose of azathioprine reduced to one-fourth to one-third the usual amount to prevent excessive toxicity. 

Combined administration of azathioprine and allopurinol may result in severe pancytopenia. The dose of Azathioprine should be reduced by two-thirds when given with allopurinol. Azathioprine rarely causes liver dysfunction, frequently manifested by an isolated rise in ALT and bilirubin. With the introduction of mycophenolate mofetil, azathioprine may be relegated to a second-line anti metabolite for the prevention of graft rejection. 

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