MAGNESIUM HYDROXIDE AND OMEPRAZOLE AND SODIUM BICARBONATE
Clinical safety rating: safe
Can decrease the levels of many drugs by increasing urinary pH Can cause metabolic alkalosis and fluid overload.
Magnesium hydroxide is an antacid that neutralizes gastric acid, increasing gastric pH. Omeprazole is a proton pump inhibitor (PPI) that irreversibly inhibits the H+/K+ ATPase enzyme system at the secretory surface of gastric parietal cells, blocking the final step of acid secretion. Sodium bicarbonate is a systemic antacid that neutralizes gastric acid and also provides alkalinization of urine.
| Metabolism | Omeprazole is extensively metabolized in the liver via CYP2C19 and CYP3A4; its metabolites are inactive. Magnesium hydroxide and sodium bicarbonate are not metabolized; they act locally and are partially absorbed. Sodium bicarbonate is converted to carbon dioxide and water via carbonic anhydrase. |
| Excretion | Magnesium hydroxide: primarily fecal (unabsorbed magnesium), renal (absorbed magnesium); omeprazole: renal (~77% as metabolites) and fecal (~23%); sodium bicarbonate: renal (as bicarbonate or CO2). |
| Half-life | Magnesium hydroxide: not applicable (local action); omeprazole: 0.5-1 hour (terminal); sodium bicarbonate: not applicable (buffering agent). Omeprazole's half-life is short but pharmacodynamic effect (acid suppression) lasts ~24 hours due to covalent binding to proton pumps. |
| Protein binding | Magnesium hydroxide: negligible; omeprazole: 95% (albumin and alpha1-acid glycoprotein); sodium bicarbonate: negligible. |
| Volume of Distribution | Magnesium hydroxide: not applicable (local); omeprazole: 0.3-0.5 L/kg (extensive tissue distribution); sodium bicarbonate: 0.5-1 L/kg (total body water). |
| Bioavailability | Magnesium hydroxide: not absorbed orally; omeprazole: 30-40% (oral, delayed-release formulation); sodium bicarbonate: 100% (oral, completely absorbed). |
| Onset of Action | Magnesium hydroxide: 0.5-3 hours (oral laxative); omeprazole: 1-2 hours (oral, acid suppression); sodium bicarbonate: <15 minutes (oral antacid). |
| Duration of Action | Magnesium hydroxide: 4-6 hours (laxative); omeprazole: 24 hours (acid suppression, sustained by proton pump inactivation); sodium bicarbonate: 1-2 hours (antacid). |
One tablet (containing 400 mg magnesium hydroxide, 20 mg omeprazole, 1000 mg sodium bicarbonate) orally once daily, taken at least 1 hour before a meal.
| Dosage form | TABLET |
| Renal impairment | Contraindicated in severe renal impairment (eGFR <30 mL/min/1.73m²) due to risk of magnesium accumulation and sodium overload. For eGFR 30-59 mL/min/1.73m², reduce dose to one tablet every other day and monitor serum magnesium and sodium. |
| Liver impairment | Child-Pugh A: No adjustment. Child-Pugh B: Reduce omeprazole dose to 10 mg (not available in this combination) or consider alternative; use with caution. Child-Pugh C: Contraindicated due to omeprazole accumulation. |
| Pediatric use | Not recommended for use in pediatric patients (safety and efficacy not established). |
| Geriatric use | Use with caution due to increased risk of electrolyte imbalance (hypermagnesemia, metabolic alkalosis) and renal impairment. Consider reducing dose to one tablet every other day. Monitor renal function and serum electrolytes. |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Can decrease the levels of many drugs by increasing urinary pH Can cause metabolic alkalosis and fluid overload.
| FDA category | Animal |
| Breastfeeding | Omeprazole is excreted in breast milk in low amounts (M/P ratio ~0.5); magnesium hydroxide and sodium bicarbonate are poorly absorbed; considered compatible with breastfeeding, but monitor infant for diarrhea or electrolyte imbalance. |
| Teratogenic Risk | First trimester: No evidence of teratogenicity from omeprazole or magnesium hydroxide; sodium bicarbonate may cause metabolic alkalosis. Second and third trimesters: Omeprazole is considered low risk; magnesium hydroxide can cause hypotonia and respiratory depression in neonates with prolonged use; sodium bicarbonate may lead to fluid overload or alkalosis. |
■ FDA Black Box Warning
None
| Common Effects | hyperkalemia |
| Serious Effects |
Hypersensitivity to any component; Concurrent use of rilpivirine-containing products; Severe renal impairment (CrCl <30 mL/min) due to risk of magnesium toxicity; Sodium-restricted diet (due to sodium content); Patients with metabolic alkalosis; Children under 12 years for over-the-counter use (varies by product).
| Precautions | Long-term use (≥1 year) may increase risk of osteoporosis-related fractures; hypomagnesemia with prolonged PPI use; cyanocobalamin (vitamin B12) deficiency with long-term acid suppression; magnesium hydroxide may cause diarrhea; sodium bicarbonate may cause metabolic alkalosis, fluid retention, and worsen hypertension or heart failure; acute interstitial nephritis reported with PPIs; monitor renal function; interaction with clopidogrel (omeprazole reduces clopidogrel's active metabolite); increased risk of Clostridium difficile infection; avoid concurrent use of atazanavir or nelfinavir. |
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| Fetal Monitoring | Monitor maternal serum electrolytes (sodium, magnesium, calcium) and acid-base status; fetal ultrasound for growth if prolonged use; assess neonatal respiratory and muscle tone at delivery with high-dose magnesium. |
| Fertility Effects | No known adverse effects on fertility from omeprazole or antacids; sodium bicarbonate may affect sperm pH in high doses. |