Drugs online research references
IARC Sci Publ. 1991;(105):187-91.
Bacterial formation of N-nitroso compounds in the rat stomach after omeprazole-induced achlorhydria.
Calmels S, Bereziat JC, Ohshima H, Bartsch H.
International Agency for Research on Cancer, Lyon, France.
N-Nitrosamine formation by bacteria in the achlorhydric stomach has been proposed as an important factor in the development of gastric cancer. Thus, the effect of the presence of bacteria in the stomach on endogenous nitrosation was investigated in rats given omeprazole (an inhibitor of gastric H+, K((+)-ATPase) which reduces gastric secretion sufficiently to allow survival of a bacterial suspension of Escherichia coli or Pseudomonas. When rats were given both thiazolidine 4-carboxylic acid and nitrate, greater endogenous nitrosamine formation was observed in rats receiving omeprazole and an E. coli suspension than in control or omeprazole-treated rats. A similar result was obtained when rats were given morpholine and nitrate. Since the endogenous formation of N-nitrosomorpholine (NMOR) can be evaluated more precisely from the levels of its urinary metabolites, N-nitrosohydroxyethylglycine (NHEG), the metabolism of NMOR was studied in omeprazole-treated rats. In this preliminary study, we showed that 60% of an oral dose of NMOR was excreted as NHEG, while in rats with a higher gastric pH 20% was excreted as NHEG. The amount of endogenously formed NMOR was increased in omeprazole-treated rats given morpholine and nitrite together with bacteria, and greater excretion of unchanged urinary NMOR was observed. Thus, as shown in this in-vivo model, bacteria efficiently reduce nitrate to nitrite and catalyse nitrosation, resulting in increased endogenous formation of N-nitroso compounds in the achlorhydric stomach.
online pharmacy ref source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=1855848&dopt=Abstract
note: kwd match prilosec online literature
Carcinogenesis. 1991 Mar;12(3):435-9.
Bacterial formation of N-nitroso compounds from administered precursors in the rat stomach after omeprazole-induced achlorhydria.
Calmels S, Bereziat JC, Ohshima H, Bartsch H.
International Agency for Research on Cancer, Lyon, France.
The role of bacteria in catalysing intragastric formation of N-nitrosothiazolidine-4-carboxylic acid and N-nitrosomorpholine was investigated in a rat model of omeprazole-induced achlorhydria. Omeprazole-treated rats gavaged with nitrosation-proficient bacteria were treated with nitrosamines and/or precursors and compared to control animals that received no omeprazole treatment/no bacteria. Rats given thiazolidine-4-carboxylic acid, nitrate and 10(11) cells of Escherichia coli, had a five times higher endogenous formation of N-nitrosothiazolidine-4-carboxylic acid as compared to controls. Endogenous formation of N-nitrosomorpholine was quantified by measuring its urinary metabolite N-nitroso-(2-hydroxyethyl)glycine; when rats were given morpholine and nitrite together with E. coli or Pseudomonas aeruginosa endogenous N-nitrosomorpholine formation was increased approximately 2.5-fold as compared to controls. In the same experiment, a higher excretion of unchanged N-nitrosomorpholine was also observed in omeprazole-treated rats receiving bacteria as compared to controls. Rats given morpholine, nitrate and E. coli or P. aeruginosa, excreted three times higher levels of N-nitrosomorpholine as compared to controls. These results conclusively demonstrate that nitrosation-proficient bacteria are capable of increasing intragastric formation of N-nitrosothiazolidine-4-carboxylic acid and N-nitrosomorpholine. These N-nitrosamines are formed from nitrate (or nitrite) and the respective amino precursor via reduction of nitrate into nitrite and bacterial nitrosation catalysis.
online pharmacy ref source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=1901250&dopt=Abstract
note: kwd match prilosec online literature
Digestion. 1991;48(3):179-84.
Effect of omeprazole on nocturnal intragastric pH in cirrhotics with inadequate antisecretory response to ranitidine.
Walker S, Klotz U, Sarem-Aslani A, Treiber G, Bode JC.
Department of Gastroenterology, Robert Bosch Hospital, Stuttgart, FRG.
Failure of acid suppression by H2-receptor antagonists has been observed, and recently we have found a higher frequency of patients with inadequate antisecretory response among patients with cirrhosis of the liver. In the present study comprising 16 cirrhotics with inadequate antisecretory response to 300 mg of ranitidine, we tested the effect of 40 mg omeprazole. Nighttime intragastric pH was continuously monitored, and a rise in the intragastric pH above 4.0 for more than 6 h following the oral dose at 18.00 h was considered as response. The median pH profile during the omeprazole treatment was significantly higher than with ranitidine (p less than or equal to 0.001). In contrast to 300 mg ranitidine, which despite sufficient plasma levels 2 and 4 h after intake (762 +/- 431 and 802 +/- 668 ng/ml) resulted in a rise in the nighttime intragastric pH above 4 only for 1.8 +/- 1.7 h, after omeprazole for at least 5 days, the intragastric pH was for 10.1 +/- 2.4 of 12 h above 4 during the night (p less than 0.001). The omeprazole plasma levels were 611 +/- 323 and 881 +/- 533 ng/ml after 2 and 4 h. The data obtained with intragastric pH monitoring indicate that the H+K(+)-ATPase inhibitor omeprazole is able to overcome the H2-blocker resistance in cirrhotics.
online pharmacy ref source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=1916039&dopt=Abstract
note: kwd match prilosec online literature
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