Miracid Mechanism of Action

Pharmacodynamics: Mechanism of Action: Omeprazole is a selective and irreversible proton pump inhibitor. Omeprazole suppresses gastric acid secretion by specific inhibition of the hydrogen-potassium adenosine triphosphatase (H⁺, K⁺-ATPase) enzyme system found at the secretory surface of parietal cells. It inhibits the final transport of hydrogen ions (via exchange with potassium ions) into the gastric lumen. The inhibitory effect is dose-related. Omeprazole inhibits both basal and stimulated acid secretion irrespective of the stimulus.
Pharmacokinetics: Omeprazole, the prototype drug of proton pump inhibitors (PPIs), is metabolized primarily by CYP2C19 to 5-hydroxyomeprazole. 5-hydroxyomeprazole is then transformed into 5-hydroxyomeprazole sulfone by CYP3A4.
Omeprazole is metabolized directly in part by CYP3A4 to omeprazole sulfone, then transformed into 5-hydroxyomeprazole sulfone by CYP2C19.
Absorption: T_max: delayed-release capsules: 30 minutes to 3.5 hours.
Bioavailability: 30% to 40%; Hepatic dysfunction ~100%; Asian: AUC increased upto fourfold compared to Caucasians.
Food effect: the rate, but not the extent, of absorption is affected by food.
Distribution: V_d: 0.34 to 0.37 L/kg.
Protein binding: 95% to 96%.
Metabolism: Hepatic, extensive first pass.
Excretion: Bile: 16% to 19%.
Fecal: 18% to 23%.
Renal: 70% to 77%; very little as unchanged drug.
Total body clearance: 500 to 600 mL/minute.
Elimination Half life: Adults: 0.5 to 1 hour.
Chronic liver disease: 3 hours.
Geriatric patient: 1 hour.