Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0344307 (analgesia)
 28,200 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

We have studied the influence of maternal serum B12 concentration on the inactivation of placental methionine synthase activity by nitrous oxide in an obstetric population. This group was known to include patients with a wide range of B12 values. Over 70% of patients were given nitrous oxide either for analgesia during labour or for delivery by Caesarean section, for periods ranging from a few minutes to 11 h. Patients undergoing normal delivery and Caesarean section under extradural anaesthesia served as controls. There was a highly significant relation between placental methionine synthase activity and duration of exposure to nitrous oxide. Inactivation was slower than that described for the liver, which may reflect the intermittent use. There was also a significant relation between maternal B12 and placental methionine synthase activity, but there was a wide scatter of results and the data were not thought to be predictive. There was evidence that inactivation by nitrous oxide was more rapid in patients with small concentrations of B12. We conclude that some patients with reduced serum concentrations of B12 may be at a disadvantage with nitrous oxide anaesthesia.
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PMID:Influence of vitamin B12 status on the inactivation of methionine synthase by nitrous oxide. 163 9

Nitrous oxide (N2 O) is frequently used for short anesthesia/analgesia in children undergoing painful or repetitive procedures. Children with acute lymphoblastic leukemia (ALL) require repeated lumbar punctures with direct instillation of intrathecal chemotherapy, usually the anti-folate agent methotrexate, during their treatment. These procedures are frequently performed under anesthesia. Concerns have been intermittently raised about a drug interaction between methotrexate and N2 O that may potentiate the undesirable side effects of methotrexate, including neurotoxicity. However, the clinical evidence consists mainly of isolated case reports leading to a lack of consensus among pediatric anesthetists about the relative risk benefits of using N2 O in children with ALL. In this article, we review the biochemical basis and scientific observations that suggest a significant interaction between N2 O and methotrexate due to their dual inhibition of the key enzyme methionine synthase. The possible role of this interaction in potentiating neurotoxicity in children with cancer is discussed, and arguments and counterarguments about the clinical significance of this largely theoretical relationship are explored. Following comprehensive review of all the available data, we make the case for the circumstantial evidence being sufficiently compelling to prompt a review of practice by pediatric anesthetists and call for a precautionary approach by avoiding the use of N2 O in children receiving concurrent methotrexate.
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PMID:Should nitrous oxide ever be used in oncology patients receiving methotrexate therapy? 3232 33