Drugs online research references
Circ Shock. 1994 Jan;42(1):39-43.
Role of xanthine oxidase inhibition in survival from hemorrhagic shock.
Mannion D, Fitzpatrick GJ, Feeley M.
Department of Anesthesia and Critical Care, Meath Hospital, Trinity College, Dublin, Ireland.
The irreversible loss of adenine nucleotides and the formation of free radicals have both been suggested as causes of irreversibility following prolonged hemorrhagic shock. This study was performed to assess the effect of xanthine oxidase inhibition (allopurinol 50 mg/kg/day), free radical scavenging (superoxide dismutase 15,000 u/kg, catalase 15,000 u/kg, dimethylsulfoxide 20 mg/kg, and alpha tocopherol 100 mg/kg/day) or both, on the 24-hr survival of dogs subjected to irreversible haemorrhagic shock. Twenty anesthetized dogs were bled to a mean arterial pressure of 30 mm Hg for 4 hr. The dogs were allocated to a control, an allopurinol pretreated, a free radical scavenger, or a combined treatment group. Both groups pretreated with allopurinol had significantly improved survival (P < 0.05) over that seen in the control group, but the free radical scavenger treated group was not significantly different from the control group. This study demonstrates the beneficial effect of xanthine oxidase inhibition on survival, and suggests that it may be due to preservation of adenine nucleotides rather than prevention of free radical formation.
online pharmacy ref source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=8149508&dopt=Abstract
Can J Biochem. 1976 Dec;54(12):1055-60.
Purine catabolism in man: inhibition of 5'-phosphomonesterase activities from placental microsomes.
Fox IH, Marchant PJ.
The 5'-phosphomonoesterase activity of 5'-nucleotidase (EC 3.1.3.5) and alkaline phosphatase (EC 3.1.3.5) participates in the catabolism of purine ribonucleotides to uric acid in humans. Initial velocity studies of 5'-nucleotidase suggest a sequential mechanism of interaction between AMP nad MgCl2, with a Km of 14 and 3 muM, respectively. With product inhibition studies the apparent Ki's for adenosine, inosine, cytidine, and inorganic phosphate were 0.4, 3.0, 5.0, and 42 mM, respectively. A large number of nucleoside mono-, di-, and tri-phosphate compounds were inhibitors of the enzyme. Allopurinol ribonucleotide, ADP, or ATP were competitive inhititors when AMP was the substrate, with a Ki slope of 120 muM. The phosphomonoesterase activity of human placental microsomal alkaline phosphatase had a pH optimum of 10.0 and had only 18% of maximum activity at pH 7.4. Substrates and inhibitors included almost any phosphorylated compound. The Km for AMP was 0.4 mM and the apparent Ki for Pi was 0.6 mM. Activity was increased only 19% by 5 mM MgCl2. These observations suggest that 5'-nucleotidase and alkaline phosphatase may be inhibited by ATP and Pi, respectively, under normal intracellular conditions, and that AMP may be preferentially hydrolyzed by 5'-nucleotidase.
online pharmacy ref source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=1016916&dopt=Abstract
Pediatrics. 1994 Dec;94(6 Pt 1):820-3.
The pharmacokinetics of injectable allopurinol in newborns with the hypoplastic left heart syndrome.
McGaurn SP, Davis LE, Krawczeniuk MM, Murphy JD, Jacobs ML, Norwood WI, Clancy RR.
Division of Neurology, Children's Hospital of Philadelphia.
OBJECTIVE. The purpose of this investigation was to determine the pharmacokinetic disposition of intravenous allopurinol and its metabolite oxypurinol in neonates with the hypoplastic left heart syndrome (HLHS) and to evaluate the subsequent degree of xanthine oxidase inhibition using serum uric acid as a marker. METHODS. Pharmacokinetic data were evaluated in 12 stable preoperative neonates with HLHS after a single intravenous allopurinol administration of 5 mg/kg or 10 mg/kg. Pharmacokinetic parameters were determined for elimination half-life, clearance, volume of distribution, and mean residence time. Xanthine oxidase inhibition, measured by serum uric acid reduction, was also measured. RESULTS. Pharmacokinetic parameters revealed no statistically significant differences between a 5-mg/kg and 10-mg/kg dose of intravenous allopurinol on elimination half-life, clearance, volume of distribution, and mean residence time. Mean serum uric acid levels were significantly reduced from baseline by 39.99 and 42.94%, respectively, in the 5- and 10-mg/kg treatment groups. DISCUSSION. The enzyme xanthine oxidase plays a key biochemical role in the generation of toxic oxygen-derived free radicals during ischemia-reperfusion conditions. Allopurinol and its active metabolite oxypurinol inhibit xanthine oxidase, and significantly reduce the conversion of hypoxanthine to xanthine and xanthine to uric acid. Cell injury may be caused by toxic oxygen free radicals produced by ischemia-reperfusion injury such as could occur during the repair of HLHS under hypothermic total circulatory arrest. We hypothesize that allopurinol may provide protection from cellular injury in this clinical context.
online pharmacy ref source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=7970996&dopt=Abstract
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