Additionally, most sources recommend that after taking omeprazole, at least 30 minutes should be allowed to elapse before eating (at least 60 minutes for immediate-release omeprazole plus sodium bicarbonate products, such as Zegerid), though some sources say that with delayed-release forms of omeprazole, waiting before eating after taking the medication is not necessary.Omeprazole is completely metabolized by the cytochrome P450 system, mainly in the liver, by CYP2C19 and CYP3A4 isoenzymes. Identified metabolites are the sulfone, the sulfide, and hydroxy-omeprazole, which exert no significant effect on acid secretion. About 77% of an orally given dose is excreted as metabolites in the urine, and the remainder is found in the feces, primarily originating from bile secretion. Omeprazole has a half life of 0.5 to 1 hour. The pharmacological effects of omeprazole last longer as it is covalently bonded to proton pump on parietal cells to induce effects. Chemistry
Omeprazole contains a tricoordinated sulfinyl sulfur in a pyramidal structure and therefore can exist as either the (S)- or (R)-enantiomers. Omeprazole is a racemate, an equal mixture of the two. In the acidic conditions of the canaliculi of parietal cells, both enantiomers are converted to achiral products (sulfenic acid and sulfenamide configurations) which react with a cysteine group in H+/K+ ATPase, thereby inhibiting the ability of the parietal cells to produce gastric acid. AstraZeneca also developed esomeprazole (Nexium) which is a eutomer, purely the (S)-enantiomer, rather than a racemate like omeprazole.
Pregnancy and breastfeeding
The safety of using omeprazole has not been established in pregnant or breastfeeding women. Epidemiological data do not show an increased risk of major birth defects after maternal use of omeprazole during pregnancy.No clinical trials have deeply evaluated the potential consequences of the use of omeprazole in breastfeeding. However, the pharmacokinetics of the omeprazole molecule strongly suggest the safety of omeprazole use during breastfeeding:

Omeprazole has a high plasma protein binding rate (95%), indicating that a little amount of drug is transferred to the milk duct during breast milk formation. Omeprazole needs to be administered in an enteric-coated formulation due to its rapid degradation in the acidic conditions of the stomach. This suggests that most of the free molecules ingested by the infant are likely degraded before being absorbed.Omeprazole at normal doses is likely safe during breastfeeding. Interactions
Important drug interactions are rare. However, the most significant major drug interaction concern is the decreased activation of clopidogrel when taken together with omeprazole. Although still controversial, this may increase the risk of stroke or heart attack in people taking clopidogrel to prevent these events. This interaction is possible because omeprazole is an inhibitor of the enzymes CYP2C19 and CYP3A4. Clopidogrel is an inactive prodrug that partially depends on CYP2C19 for conversion to its active form.