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. |
| Molecular Weight | 713.12 |
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 | Available data do not suggest an increased risk of major birth defects. Animal studies have not shown fetal harm at clinically relevant doses. |
| 2nd trimester | No evidence of fetal harm in human studies; considered safe if clinically indicated. |
| 3rd trimester | Generally considered safe; use only if clearly needed due to potential associations with bone density reduction in prolonged use. |
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 |
| Placental transfer | Omeprazole crosses the placenta in humans; fetal plasma concentrations are about 17% of maternal concentrations based on limited data. |
■ FDA Black Box Warning
None.
| Common Effects | erosive esophagitis |
| Serious Effects |
Hypersensitivity to omeprazole or any component of the formulationConcomitant use with rilpivirine
| 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 |
| Food/Dietary | Omeprazole should be taken on an empty stomach at least 30 minutes before a meal for optimal absorption. Food does not significantly alter absorption but delays its effect. Avoid high-fat meals immediately before dosing. Concomitant intake of antacids should be separated by at least 1 hour. No specific dietary restrictions are required, but acidic beverages (e.g., orange juice) may be less effective for symptom relief while on PPI therapy. |
Loading safety data…
| Breastfeeding |
| Omeprazole is excreted into human breast milk in low amounts; estimated infant dose is less than 7% of the maternal weight-adjusted dose. Not expected to cause adverse effects in infants. Caution in premature infants or those with renal impairment. |
| Lactation Rating | L2 |
| 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. |
| 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. |
| Clinical Pearls | Omeprazole magnesium is a proton pump inhibitor (PPI) that should be taken at least 30 minutes before a meal, typically breakfast, for maximal efficacy. It is available in delayed-release capsules and powder for oral suspension. Use caution in patients with osteoporosis, hypomagnesemia, or those on long-term therapy (>3 months) as it may increase fracture risk, risk of Clostridium difficile infection, and vitamin B12 deficiency. Magnesium-containing antacids should be avoided within 1 hour of dosing. Do not crush or chew capsules; the oral suspension should be administered with applesauce or apple juice if needed. |
| Patient Advice | Take omeprazole exactly as prescribed, usually once daily before a meal. · Swallow the capsule whole; do not crush, chew, or open it. · If you miss a dose, take it as soon as you remember unless it is almost time for the next dose. Do not take two doses simultaneously. · Report severe diarrhea, bone pain, or signs of low magnesium (muscle cramps, irregular heartbeat) to your healthcare provider. · Do not use over-the-counter omeprazole for longer than 14 days without consulting a doctor. · Avoid alcohol and NSAIDs (e.g., ibuprofen, naproxen) as they may worsen stomach irritation. · Inform your doctor about all other medications, especially clopidogrel, warfarin, or methotrexate. |