Omeprazole irreversibly binds to and inhibits the H+/K+ ATPase proton pump in gastric parietal cells. This is the final common pathway of gastric acid secretion, regardless of stimulus (histamine, gastrin, or acetylcholine). The effect persists until new proton pumps are synthesized, which gives the drug its long pharmacodynamic duration despite a short plasma half-life. Omeprazole is acid-labile and requires enteric coating to survive gastric acid for absorption.

• GERD
• Peptic ulcer disease (gastric and duodenal)
• Helicobacter pylori eradication as part of combination therapy
• Zollinger-Ellison syndrome
• Stress ulcer prophylaxis
• Operational acid suppression during prolonged deployment when stress and NSAID use drive symptomatic disease

• Known hypersensitivity to omeprazole or other PPIs
• Concurrent use with rilpivirine

Common: headache, abdominal pain, diarrhea, nausea, flatulence. Long-term risks (over 1 year of use): vitamin B12 deficiency, hypomagnesemia, hypocalcemia and fracture risk (hip, wrist, spine), C. difficile infection, community-acquired pneumonia, and acute interstitial nephritis (rare). Drug interactions: reduces clopidogrel activation through CYP2C19 inhibition (clinical significance is debated but most guidelines recommend a different antiplatelet or a different PPI for patients on clopidogrel). Increases methotrexate, warfarin, phenytoin, and diazepam levels. Reduces absorption of pH-dependent drugs (ketoconazole, atazanavir, iron, calcium carbonate, B12, levothyroxine). Plasma half-life 0.5 to 1 hour but pharmacodynamic duration is 24 hours. CYP2C19 poor metabolizers (about 3 percent of Caucasians, 15 to 20 percent of Asians) have higher exposure. Pregnancy Category C. Probably compatible with lactation. Reserve chronic daily use for symptomatic disease or NSAID-associated risk - the long-term safety signal is real.

Children 1 to 16 years, weight-based: 5 to less than 10 kg = 5 mg daily; 10 to less than 20 kg = 10 mg daily; 20 kg or more = 20 mg daily.

Peak Effect: Plasma peak 30 minutes to 2 hours; maximal acid suppression 4 days.

Duration: 24 hours per dose despite short plasma half-life due to irreversible binding to the proton pump.

Store at room temperature (20 to 25 degrees C). Protect from light and moisture. Stable in standard aid bag conditions. Capsules and tablets are robust for operational environments.

Reconstitution:

Oral formulation. Delayed-release granules can be sprinkled on applesauce or mixed in juice if swallowing is difficult; granules must not be chewed or crushed (destroys enteric coating).

Omeprazole is not in the TCCC core formulary. It appears in tactical EMS supplemental formularies for operational acid suppression during prolonged deployment or sustained operations where stress, NSAID use, and altered eating patterns drive symptomatic GERD or peptic ulcer disease. PPI prophylaxis for stress ulcer prevention in prolonged field care after major trauma is consistent with hospital practice and may be appropriate in role 2 settings.