M L Osborne — Page 3 | Search PubMed

PubMed1981

Nitrous oxide has multiple deleterious effects on cobalamin metabolism and causes decreases in activities of both mammalian cobalamin-dependent enzymes in rats.

In man, use of the general anesthetic nitrous oxide, N2O, is associated with hematologic and neurologic abnormalities that mimic those seen in cobalamin (Cbl, vitamin B12) deficiency. We have measured a number of aspects of Cbl metabolism in rts exposed to various concentrations of N2O for various periods of time. As little as 2% N2O given for 15 h resulted in 30% inhibition of methionine synthetase (MS) in rat liver. With 50% N2O, inhibition of 70% occurred with 1 h and did not change during the next 48 h. Under these conditions, no inhibition of methylmalonyl-CoA mutase (MMCoAM) was observed. The recovery of MS activity was slow and was only 80% of control values 72 h after N2O was stopped. Studies employing rats previously injected with [57Co]Cbl showed that N2O displaced [57Co]Cbl from MS in a manner that temporally and quantitatively paralleled the loss of MS activity. Recovery of MS activity paralleled the reappearance of [57Co]Cbl on MS. N2O also caused the hepatic content of CH3-[57Co]Cbl to decrease by 20-60%. When [57Co]-Cbl was extracted from liver and analyzed by paper chromatography, [57Co]Cbl analogues were present (10-40% of total [57Co]Cbl) in rats exposed to N2O, but not in control animals. When rats were exposed to 50% N2O for 33 d, the total of endogenous Cbl and Cbl analogues in liver decreased to 35% of control values and endogenous Cbl decreased to 10% of control values. At this time, MS activity was 15% of control values and MMCoAM was only 26% of control values. We conclude that N2O causes multiple defects in Cbl metabolism that include the following: (a) rapid inhibition of MS activity with a slow recovery when N2O is stopped; (b) displacement of Cbl from MS; (c) decreased CH3-Cbl; (d) conversion of Cbl to Cbl analogues; (e) the gradual development of Cbl deficiency and (f) an eventual decrease in MMCoAM activity with a further decrease in MS activity.

5-Methyltetrahydrofolate-Homocysteine S-Methyltran↗

PubMed1977

Pimozide versus fluphenazine in ambulatory schizophrenics: A 12-month comparison study.

In this study, chronic schizophrenic outpatients who had been maintained on various neuroleptics for an average of about 4 years had their previous medications (approximately equivalent to 695 mg of chlorpromazine per day) changed abruptly to either pimozide or fluphenazine given in single daily oral doses on a double-blind basis for a period of 52 weeks. Average daily doses were pimozide 9.6 mg and fluphenazine 12.5 mg. Measurements of the therapeutic effects of the two drugs were made immediately prior to starting the study, at the end of the 2nd and 4th weeks, and thereafter every 4th week to the end of the study. Three psychometric scales were used for evaluation: Brief Psychiatric Rating Scale (BPRS); Evaluation of Social Functioning (ESFR); and Clinical Global Impressions (CGI). In addition, patients participated in a Social Adjustment Inventory (SAI) evaluation. Statistical analysis with the use of several statistical techniques for between- and within-drug group comparisons revealed that pimozide and fluphenazine were equally effective in maintaining control of symptomatology of chronic schizophrenics at a level commensurate with or better than that provided by their previous medication. Side effects were characteristic of marketed neuroleptics, similar in severity and occurrence between study-drug groups, mainly extrapyramidal symptoms, and readily controlled with antiparkinsonian medication. Pimozide, slightly more potent than fluphenazine, proved to be equally effective for the long-term management of chronic schizophrenic patients.

Adult↗