Effect of once daily intravenous and oral omeprazole on 24-hour intragastric acidity in healthy subjects. Effects of omeprazole on intragastric pH and plasma gastrin are dependent on the CYP2C19 polymorphism. [Circadian monitoring of intragastric pH in evaluation of efficiency of antisecretory therapy of duodenal ulcer] Rx drugs

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Scand J Gastroenterol. 1993 Feb;28(2):179-84.
Effect of once daily intravenous and oral omeprazole on 24-hour intragastric acidity in healthy subjects.

Cederberg C, Rohss K, Lundborg P, Olbe L.

Clinical Pharmacology, Astra Hassle AB, Molndal, Sweden.

The effect of repeated once daily administration of 20 mg omeprazole orally and 10 mg and 40 mg intravenously on 24-h intragastric acidity was studied in nine healthy subjects. On day 1, 20 mg orally and 10 mg intravenously reduced integrated intragastric acidity by 18% and 15%, respectively (NS). On day 5 the reduction had increased to 60% and 53%, respectively (p < 0.05). The first dose of 40 mg intravenously produced a reduction of 71% (p < 0.05) with no further increase during continued administration. An increase in plasma omeprazole concentrations by 56% (p < 0.05) was seen during repeated dosing with 40 mg intravenously, while no significant change occurred with the two other doses. Thus once daily administration of 10 mg omeprazole intravenously produced an effect on 24-h intragastric acidity comparable to that of once daily administration of 20 mg omeprazole orally. However, for both these dosage regimens it took a few days before their maximal effect was obtained. Parenteral administration of 40 mg omeprazole produced, already on the first day of treatment, an effect similar to that seen after 5 days of oral administration of 20 mg omeprazole or intravenous administration of 10 mg and can therefore overcome this initial delay in drug action. The reduction of 24-h intragastric acidity seen in the present study appeared to be lower than that seen in a similar study in duodenal ulcer patients, a finding not explained by differences in age or pharmacokinetics.

online pharmacy ref source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=8441912&dopt=Abstract

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Gastroenterology. 2000 Sep;119(3):670-6.
Effects of omeprazole on intragastric pH and plasma gastrin are dependent on the CYP2C19 polymorphism.

Sagar M, Tybring G, Dahl ML, Bertilsson L, Seensalu R.

Center of Gastroenterology, Departments of Surgery and Medicine, Clinical Research Center, Huddinge University Hospital, Stockholm, Sweden.

BACKGROUND & AIMS: Omeprazole is metabolized by cytochrome P450 (CYP2C19). The activity of this enzyme is polymorphic, with incidences of poor metabolizers (PMs), heterozygous extensive metabolizers (EMs), and homozygous EMs in white populations of 3%, 30%, and 67%, respectively. The importance of the CYP2C19 polymorphism for the effects of omeprazole on intragastric pH and plasma gastrin concentrations has been investigated. METHODS: Twenty-five white patients were genotyped for CYP2C19 by allele-specific polymerase chain reaction amplification, and their Helicobacter pylori status was assessed by serology and with immunoblot analysis. Intragastric pH was monitored over 24 hours, and meal-stimulated plasma gastrin concentration was measured over 4 hours (AUC 4h) before (day 0) and during (day 8) treatment with 20 mg omeprazole once daily. RESULTS: Eleven patients were homozygous for the wild-type allele (wt/wt), 12 were heterozygous EMs (wt/mut), and 2 were PMs (mut/mut). Median (95% confidence interval) 24-hour intragastric pH in the heterozygous EM group was 5.5 (range, 5.1-5. 9) compared with 3.1 (range, 2.7-3.6) in homozygous EMs (P < 0.0001) at day 8. The percentage of time with intragastric pH > 4 at day 8 was significantly higher in the wt/mut than wt/wt group (72.4% vs. 37.1%; P < 0.0001). H. pylori status had less influence than CYP2C19 on intragastric acidity. Omeprazole treatment increased meal-stimulated plasma gastrin concentrations from day 0 to day 8 in the homozygous EMs and heterozygous EMs by 16% (NS) and 157% (P = 0. 002), respectively. In heterozygous EMs, the gastrin increase was more pronounced in the H. pylori-positive group (226%) than H. pylori-negative group (80%; P = 0.02). CONCLUSIONS: The effects of omeprazole on intragastric pH and plasma gastrin are dependent on the CYP2C19 polymorphism in patients with acid-related disorders.

online pharmacy ref source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=10982760&dopt=Abstract

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Klin Med (Mosk). 2002;80(2):54-6.
[Circadian monitoring of intragastric pH in evaluation of efficiency of antisecretory therapy of duodenal ulcer]

[Article in Russian]

Kolesnikova IIu, Beliaeva GS, Bordin DS.

Inhibitors of proton pump are thought "golden standard" in the treatment of ulcer. Usage of omeprasol generics in standard doses sometimes fail to adequately reduce acid production. In pain persistence in patients with duodenal ulcer receiving standard antisecretory therapy it is effective to control it with 24-h intragastric pH-metry which either indicate the necessity of dose correction or another cause of pain (concomitant affections as a rule). As shown by 24-h pH-metry, a new generic of omeprasol, omeprus, is close by effectiveness to the known drug omeaz.

online pharmacy ref source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=11898725&dopt=Abstract

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