Magnesium oxide
MAG-OX
Pronunciation: mag-NEE-zee-um OX-ide
What it isMagnesium salt acting as an osmotic laxative and repletion agent; constipation and hypomagnesemia.
Why this oneHigh elemental magnesium but poor absorption makes it more reliable as a laxative than as repletion.
What limits itDiarrhea is dose-limiting, and magnesium can accumulate dangerously when kidney function is impaired.
FDA label
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| FDA dosing | Population | Start | Target | Max |
|---|---|---|---|---|
| Antacid | Adults | 1–2 tablets QD | 1–2 tablets QD | 2 tablets/day unless directed by a physician |
Renal Undefined
Hepatic Undefined
Label does not state tablet strength (mg).
Available strengths
- tab 253, 400, 420, 440 mg
- tab 241.3 mg/1000 mg
Pregnancy Undefined
Lactation Undefined
Cost
Magnesium oxide (MAG-OX)
What pharmacies pay · NADAC 9/30/26 · OTC
| Strength | #/mo | generic $/mo | CostPlus | |
|---|---|---|---|---|
| 253 mg | tab | 30 qd | $1.15 | not offered |
| 400 mg | tab | 30 qd | $1.04 | not offered |
| 420 mg | tab | 30 qd | not offered | |
| 440 mg | tab | 30 qd | not offered | |
| 241.3 mg/1000 mg | tab | 30 qd | not offered |
Other forms: Magnesium (Mg2+)
NO BOXED WARNINGS
Principal riskDiarrhea; accumulation in renal impairment
Classes and tags
Clinical profile
Defining liabilityDiarrhea; hypermagnesemia with impaired clearance or bowel dysfunction