Magnesium Hydroxide and Atenolol: Interaction Details
AI-assisted, pharmacist-reviewed · AI content regenerated Jul 15, 2026 · Source data updated Jul 11, 2026 · Sources: FDA labeling, DDInter 2.0, cited literature
Magnesium Hydroxide
Atenolol
How we grade severity & evidence
Severity levels
- Contraindicated: These should generally not be used together.
- Major: Potentially serious — often needs a change or close monitoring.
- Moderate: Can be significant — usually manageable with monitoring.
- Minor: Usually limited clinical impact.
Evidence grades
- Established: Well documented — supported by controlled studies or strong clinical data.
- Probable: Good supporting evidence, though not definitively proven.
- Suspected: Some evidence suggests this interaction, but it is not well established.
- Possible: Limited or conflicting evidence; the interaction may occur.
- Theoretical: Predicted from the drugs' pharmacology; not yet confirmed in people.
Ratings come from the documented interaction literature and are reviewed by a pharmacist. They describe the documented risk of the combination, not what will necessarily happen to you — your dose, timing, and health picture all matter.
You're taking atenolol (a blood pressure and heart medicine) along with a magnesium-containing antacid like Milk of Magnesia. Here's the simple version: when you swallow them close together, the antacid can keep your body from absorbing as much of the atenolol. That means less of the drug gets into your blood, so it may not control your blood pressure or heart rate as well.
The good news is this is easy to work around. It's usually just about timing. Talk with your pharmacist or doctor about spacing the two apart so your atenolol still works the way it should.
Effect: Reduced atenolol efficacy via decreased GI absorption when co-administered with magnesium hydroxide (antacid).
- Mechanism: Antacid cations reduce atenolol bioavailability (lower AUC/Cmax). Atenolol is not a prodrug; reduced absorption directly lowers pharmacologic effect.
- Direction: Reduced beta-blockade (blood pressure, heart rate control).
- Onset: Rapid. Evidence: Probable. Severity: Minor.
- Management: Separate doses. Give atenolol 2 hours before or 6 hours after the magnesium-containing product. Monitor BP and HR for adequate control.
What happens
Reduced effectiveness of atenolol
Interaction Deep Dive
Research indicates that taking atenolol together with products containing aluminum, calcium, or magnesium will lower atenolol's bioavailability and may diminish how well it works21.
Why it happens (mechanism)
Decreased atenolol absorption
How to manage this interaction
This one is usually handled with timing, not by stopping either medicine. Keep taking both as prescribed.
- Take your atenolol 2 hours before or 6 hours after the magnesium-containing antacid so they aren't in your stomach at the same time.
- Watch that your blood pressure and heart rate stay controlled; your care team may monitor you more closely if needed.
- Tell your pharmacist or doctor if you notice your blood pressure creeping up or your heart rate feels higher than usual.
A quick word with your pharmacist can confirm the best schedule for your routine.
Management is individual — confirm any change with your pharmacist or prescriber.
Literature reports
2 reports — tap to read
a) Taking atenolol together with calcium carbonate has been reported to cause substantial reductions in peak plasma atenolol concentrations (by 51%) after single doses. During extended concurrent use, the atenolol half-life rose from 6.2 hours to 11 hours, which partially offset the lowered plasma levels. Hemodynamic parameters were comparable following 4 weeks of combined use. Dosage modification does not seem to be required for patients on long-term atenolol and calcium therapy. Patients with severe coronary heart disease should be given double the usual atenolol dose on the first day of calcium therapy 1.
b) Six healthy male volunteers fasted for ten hours and were subsequently administered atenolol 100 mg along with 30 mL of an antacid containing aluminum hydroxide, magnesium hydroxide, and magnesium carbonate. The systemic bioavailability of atenolol fell by an average of 33%, and the peak plasma concentration dropped by 37%. These findings indicate that atenolol absorption, which is normally 50% absorbed in the gut, may be diminished sufficiently with concurrent antacid therapy to result in reduced therapeutic effectiveness 2.
Common questions
Can I take Magnesium Hydroxide and Atenolol together?
Space them out: take atenolol 2 hours before or 6 hours after a magnesium antacid so the antacid doesn't block absorption of your heart medicine. Keep taking both as prescribed and check with your pharmacist. Always confirm with your pharmacist or prescriber before making any change.
How serious is the Magnesium Hydroxide and Atenolol interaction?
It is rated minor. Usually limited clinical impact.
How quickly could this interaction happen?
The documented onset is "rapid". Effects can appear quickly, often within about 24 hours of combining the drugs.
How is the Magnesium Hydroxide and Atenolol interaction managed?
This one is usually handled with timing, not by stopping either medicine. Keep taking both as prescribed. Take your atenolol 2 hours before or 6 hours after the magnesium-containing antacid so they aren't in your stomach at the same time. Watch that your blood pressure and heart rate stay controlled; your care team may monitor you more closely if needed. Tell your pharmacist or doctor if you notic… Management is individual — always follow your own care team's guidance.
How strong is the evidence for this interaction?
The evidence is graded "probable". Good supporting evidence, though not definitively proven.
Questions for your pharmacist
- Does my dose of Magnesium Hydroxide or Atenolol need adjusting while I take them together?
- What symptoms should prompt me to call you or my prescriber right away?
- Does the timing of my doses matter for this combination?
- Is there anything you'd monitor while I'm on both?
References (2)
- Kirch W, Schafer-Korting M, Axthelm T, et al: Interaction of atenolol with furosemide and calcium and aluminum salts. Clin Pharmacol Ther 1981; 30:429-435. PubMed
- Regardh CG, Lundborg P, & Persson BA: The effect of antacid, metoclopramide and propantheline on the bioavailability of metoprolol and atenolol. Biopharm Drug Dispos 1981; 2:79-87. DOI
Keep reading about Magnesium Hydroxide
Keep reading about Atenolol
These medications also interact with supplements
Prescription drugs aren't the whole picture — herbal and dietary supplements can interact with them too. From the evidence-graded Natural Medicines database:
major · moderate · minor — check everything you take with our drug–supplement interaction checker.
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