Omeprazole about

Cytochrome P450 2C19 Deficient activity in about 3% of Caucasian populations and in about 20% of Asian populations. Prolonged action of several CYP2C19 inactivated drugs like omeprazole or diazepam in the poor metabolizers. 

Fig. 2. Median gastric pH is elevated about 2 log by 20 mg of omeprazole in H. pylori-negative healthy subjects, and by 4 log in H. pylo-n -positive ones [based on data from 42], Hp = H. pylori, PPI = proton pump inhibitor. 

Q43 Which of the following statement(s) is (are) correct about omeprazole ... 

Diazepam (Valium, Diastat) [C-IVj [Anxiolytic, Skeletal Muscle Relaxant, Anticonvulsant, Sedative/Hypnotic/ Benzodiazepine] Uses Anxiety, EtOH withdrawal, muscle spasm, status epilepticus, panic disorders, amnesia, preprocedure sedation Action Benzodiazepine Dose Adults. Status epilepticus 5-10 mg IV/IM Anxiety 2-5 mg IM/IV Preprocedure 5-10 mg IV just prior to procedure Peds. Status epilepticus 0.5-2 mg IV/IM Sedation 0.2-0.5 mg/kg IV (onset w/in 5IV and 30 min IM duration about 1 h IV and IM) Caution [D, / -] Contra Coma, CNS depression, resp d es-sion, NAG, severe uncontrolled pain, PRG Disp Tabs 2, 5, 10 mg soln 1, 5 mg/mL inj 5 mg/mL rectal gel 2.5, 5, 10, 20 mg/mL SE Sedation, amnesia, bradycardia, i BP, rash, X resp rate Interactions T Effects W/ antihistamines, azole antifungals, BBs, CNS depressants, cimetidine, ciprofloxin, disulfiram, INH, OCP, omeprazole, phenytoin, valproic acid, verapamil, EtOH, kava kava, valman T effects OF digoxin, diuretics X effects w/ barbiturates, carbamazepine. 

At neutral pH proton pump inhibitors are chemically stable, lipid-soluble, weak bases that have no inhibitory activity. In an acid environment they become protonated and a sulfenamide is formed. This sulfenamide binds covalently to the K+H+-ATPase proton pump in the gastric parietal cells, inhibiting this enzyme irreversibly and thus the entry of H+ ions into lumen. Omeprazole metabolizes at a pH of about 3.9. 1, whereas rabeprazole metabolizes at a pH of about 4.9. Secretion of acid only becomes possible again after new molecules of K+H+-ATPase are formed. 

Omeprazole may be given by mouth as the base or magnesium salt or intravenously as the sodium salt. Doses are expressed in terms of the base. Omeprazole magnesium 10.32 mg and omeprazole sodium 10.64 mg are each equivalent to about 10 mg of omeprazole. For the relief of the acid-related dyspepsia, the drug is given in usual doses of 10 or 20 mg daily by mouth for 2-A weeks. The usual dose for the treatment of gastro-oesophageal reflux disease is 20 mg by mouth once daily for 4 weeks,... 

Solvents Prepare a mixture of dichloromethane and methanol (1 1). Standard solutions Dissolve an accurately weighed quantity of USP Omeprazole RS in Solvent, and mix to obtain Standard solution A having a known concentration of about 0.5 mg/ml. Dilute this solution quantitatively with Solvent to obtain Standard solution B and Standard solution C having known concentrations of about 0.15 and 0.05 mg/ml, respectively. 

Test solution Dissolve an accurately weighed quantity of omeprazole in Diluent to obtain a solution containing about 0.16 mg/ml [Note Prepare this solution fresh]. 

Procedure Inject equal volumes (about 40 p ) of the Test solution and Diluent into the chromatograph, and allow the Test solution to elute for not less than two times the retention time of omeprazole. Record the chromatograms, and measure the peak responses. Calculate the percentage of each impurity in the portion of omeprazole taken by the formula ... 

Assay preparation Transfer about 100 mg of Omeprazole, accurately weighed, to a 50-ml volumetric flask, dissolve in and dilute with Diluent to volume, and mix. Transfer 5 ml of this solution to a 50-ml volumetric flask, dilute with Diluent to volume, and mix. 

Procedure Separately inject equal volumes (about 20 p ) of the Standard solution and Test solution into the chromatograph, record the chromatograms, and measure the responses for the major peaks. Calculate the quantity, in mg, of omeprazole (Ci7H19N303S) dissolved in the medium by the formula ... 

Standard solution 1 (for Capsules labeled 10 mg) Dissolve an accurately weighed quantity of USP Omeprazole RS in alcohol to obtain a solution having a known concentration of about 2 mg/ml. Dilute with pH 6.8 Phosphate buffer quantitatively, and stepwise if necessary, to obtain a solution having a known concentration of about 0.01 mg/ml. Immediately add 2 ml of 0.25 M sodium hydroxide to 10 ml of this solution, and mix. [Note Do not allow the solution to stand before adding the sodium hydroxide solution.]... 

Procedure Proceed as directed for Acid resistance stage with a new set of capsules from the same batch. After 2 h, replace the acid Medium with the buffer Medium and continue the test for 45 more minutes. Determine the amount of C17H19N3O3S dissolved from UV absorbances at the wavelength of maximum absorbance at about 305 nm on portions of the solutions under test passed through 0.2-p.m nylon filter, in comparison with a Standard solution having a known concentration of USP Omeprazole RS and the same Medium. 

Assay preparation Weigh and mix the contents of not fewer than 20 Capsules. Transfer an accurately weighed portion of the mixture, equivalent to about 20 mg of omeprazole, to a 100-ml volumetric flask, add about 50 ml of Diluent, and sonicate for 15 min. Cool, dilute with Diluent to volume, mix, and pass through a membrane filter having 0.45 /im or finer porosity. [Note Bubbles may form just before bringing the solution to volume. Add a few drops of dehydrated alcohol to dissipate the bubbles if they persist for more than a few minutes]. 

Murakami et al. [82] developed and validated a sensitive HPLC technique to quantify omeprazole in delayed release tablets. The analysis was carried out using a RP-Cig column with UV-VIS detection at 280 nm. The mobile phase was diluted with phosphate buffer (pH 7.4) and acetonitrile (70 30) at a flow-rate of 1.5 ml/min. The parameters used in the validation process were linearity, range, quantification limit, accuracy, specificity, and precision. The retention time of omeprazole was about 5 min with symmetrical peaks. The linearity in the range of 10-30 ng/ml presented a correlation coefficient of 0.9995. The excipients in the formulation did not interfere with the analysis and the recovery was quantitative. Results were satisfactory and the method proved to be adequate for quality control of omeprazole delayed-release tablets. 

Gyllenhaal and Vessman have described the packed-column SFC of omeprazole and related compunds using an amino column with triethyla-mine- and methanol-modified carbon dioxide as the mobile phase [42]. Triethylamine (1%) was added to the methanol. The method was compared with an existing HPLC method, and it was concluded that SFC was about... 

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