Omeprazole

DescriptionOmeprazole is a potent gastric antisecretory agent with selective inhibitory effect on the H+,K+-ATPase proton pump. It is highly effective in the treatment of duodenal ulcer and Zollinger-Ellison syndrome, and is reportedly superior to ranitidine in the management of reflux esophagitis.

HistoryOmeprazole was first approved by the FDA in 1989 in the form of extended-release capsules for the treatment of acid-related disorders. Brand name Prilosec, it was initially used over-the-counter (OTC) for adults to help control heartburn that occurs two or more days a week.

UsesOmeprazole is a proton pump inhibitor used to treat diseases like gastroesophageal reflux disease (GERD), used for gastric and duodenal ulcers, reflux or erosive esophagitis, and Zollinger-Ellison syndrome. It is also effective for gastric and duodenal ulcers that are ineffective with H2 receptor antagonists. Injections of Omeprazole can also be used for: 1 gastrointestinal bleeding, such as peptic and anastomic ulcer bleeding, and the prevention of severe diseases (such as cerebral hemorrhage, severe trauma, etc.) and gastric surgery caused by upper intestinal bleeding; 2 acute gastric mucosal damage complicated by stress or nonsteroidal anti-inflammatory drugs; 3 general anesthesia, post-surgery, or coma patients, to prevent acid reflux and aspiration pneumonia; 4 Combined with amoxicillin and clarithromycin, or with metronidazole and clarithromycin, it can effectively kill Helicobacter pylori (Hp).

General DescriptionOmeprazole, 5-methoxy-2-(((4-methoxy-3, 5-dimethyl-2-pyridinyl)methyl) sulfinyl)-1Hbenzimidazole(Losec), is a white to off-white crystallinepowder with very slight solubility in water. Omeprazole isan amphoteric compound (pyridine N, pKa 4.06; benzimidazoleN-H, pKa 0.79), and consistent with the proposedmechanism of action of the substituted benzimidazoles, isacid labile. Hence, the omeprazole product is formulatedas delayed-release capsules containing enteric-coatedgranules.The absolute bioavailability of orally administeredorneprazole is 30% to 40% related to substantial first-passbiotransformation. The drug has a plasmahalf-life of about 1 hour. Most (77%) of an oral dose ofomeprazole is excreted in the urine as metabolites with insignificantantisecretory activity. The primary metabolitesof omeprazole are 5-hydroxyomeprazole (CYP2C19) andomeprazole sulfone (CYP3A4). The antisecretory actions ofomeprazole persist for 24 to 72 hours, long after the drughas disappeared from plasma, which is consistent with itssuggested mechanism of action involving irreversible inhibitionof the proton pump.Omeprazole is approved for the treatment of heartburn,GERD, duodenal ulcer, erosive esophagitis, gastric ulcer,and pathological hypersecretory conditions.

PreparationThe antiulcer agent omeprazole is produced from 2,3,5-trimethylpyridine N-oxide.Synthesis and Structure of OmeprazoleSteps: 2-(Lithium methyl sulphinyl)-5-methoxy-1H benzimidazole 20g was reacted with 2-chloro-3,5-dimethyl-4-methoxy pyridine 21 g to form sulphide intermediate and then converted to Omeprazole when treated with m-CPBA which used as anoxidizingagents. The acetamide-sulfide compounds modification are oxidised to form the amide sulfinyl compound and gives the sulfinyl carboxylate or salts upon alkaline hydrolysis.On further decarboxylation leads to the target molecules. The residual, unreacted salt, inorganic by-products and other minor by-products can be easily purified by a simple washing from omeprazole or lansoprazole. The amide compounds containing crystalline solids as opposed to the sulphide and sulfoxides of the reported procedures.DOI: http://dx.doi.org/10.20902/IJPTR.2019.120307