OMEPRAZOLE MAGNESIUM
Clinical safety rating: safe
Can reduce absorption of drugs requiring gastric pH for absorption (eg ketoconazole) May increase risk of Clostridium difficile-associated diarrhea and bone fractures with long-term use.
Omeprazole magnesium is a proton pump inhibitor (PPI) that irreversibly inhibits the H+/K+ ATPase enzyme system at the secretory surface of gastric parietal cells, suppressing gastric acid secretion.
| Metabolism | Primarily metabolized by CYP2C19 and CYP3A4 in the liver; also undergoes sulfation. |
| Excretion | Renal: 77% as metabolites; biliary/fecal: 16.7% as metabolites; active drug not excreted unchanged. |
| Half-life | Terminal elimination half-life: 0.5-1 hour (fast metabolizers); 2-3 hours (slow metabolizers); clinical context: prolonged in hepatic impairment, no significant accumulation with once-daily dosing due to irreversible inhibition of H+/K+-ATPase. |
| Protein binding | 95-96% bound to human serum albumin; also binds to alpha-1-acid glycoprotein. |
| Volume of Distribution | Vd: 0.3-0.37 L/kg; distributes into extracellular fluid; clinical meaning: not extensive tissue distribution. |
| Bioavailability | Oral: 30-40% (extensive first-pass metabolism); IV: 100%. |
| Onset of Action | Oral: peak acid suppression at 2-4 hours; symptom relief within 1-2 days for GERD; IV: peak effect within 30 minutes. |
| Duration of Action | Duration of acid suppression: up to 72 hours after oral dose; clinical note: once-daily dosing provides 24-hour acid control due to covalent binding to proton pumps. |
20 mg orally once daily for 4-8 weeks; for erosive esophagitis 20-40 mg orally once daily for 4-8 weeks; maintenance: 10-20 mg orally once daily; for Helicobacter pylori eradication: 20 mg orally twice daily for 10-14 days in combination with antibiotics.
| Dosage form | CAPSULE, DELAYED RELEASE |
| Renal impairment | No dose adjustment required for mild to moderate renal impairment (GFR 30-89 mL/min). For severe renal impairment (GFR <30 mL/min), maximum dose is 20 mg daily; use with caution because of limited data. |
| Liver impairment | For mild hepatic impairment (Child-Pugh class A): no dose adjustment. For moderate to severe hepatic impairment (Child-Pugh class B or C): maximum dose is 20 mg daily. |
| Pediatric use | For children 1-16 years: weight <20 kg: 10 mg orally once daily; weight ≥20 kg: 20 mg orally once daily. For erosive esophagitis: children 1 month to <1 year: 0.7 mg/kg orally once daily; children 1-16 years: weight 5 to <10 kg: 5 mg once daily; weight 10 to <20 kg: 10 mg once daily; weight ≥20 kg: 20 mg once daily. Maximum duration 4 weeks. |
| Geriatric use | No dose adjustment required; however, elderly patients may be more susceptible to adverse effects (e.g., Clostridium difficile infection, fractures, hypomagnesemia) with long-term use; use lowest effective dose for shortest duration. Max 20 mg daily is recommended for erosive esophagitis treatment. |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Can reduce absorption of drugs requiring gastric pH for absorption (eg ketoconazole) May increase risk of Clostridium difficile-associated diarrhea and bone fractures with long-term use.
| FDA category | Animal |
| Breastfeeding | Omeprazole is excreted in human breast milk; M/P ratio is approximately 0.5. Limited data suggest no adverse effects on nursing infants at maternal therapeutic doses. Consider risk-benefit. |
| Teratogenic Risk | FDA Pregnancy Category C. First trimester: No evidence of major teratogenicity in human studies; observational data show no significant increase in congenital malformations. Second and third trimesters: No known fetal toxicity; may be used if clinically indicated. Avoid high doses and prolonged use. |
■ FDA Black Box Warning
None.
| Common Effects | erosive esophagitis |
| Serious Effects |
["Hypersensitivity to omeprazole or any component","Co-administration with rilpivirine","Co-administration with nelfinavir","Co-administration with atazanavir"]
| Precautions | ["Risk of Clostridium difficile-associated diarrhea","Bone fracture risk with long-term use","Hypomagnesemia with prolonged use","Vitamin B12 deficiency with prolonged use","Acute interstitial nephritis","Cutaneous lupus erythematosus","Cyanocobalamin malabsorption"] |
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| Fetal Monitoring | No specific fetal monitoring required. Monitor maternal symptoms of acid-related disorders. In prolonged use, assess maternal bone density and vitamin B12 levels. |
| Fertility Effects | Animal studies show no impairment of fertility. Human data are lacking; no known adverse effects on fertility. |