Drug Interaction Report

Bisacodyl Rectal and Magnesium Hydroxide: Interaction Details

Name: Bisacodyl Rectal and Magnesium Hydroxide Interaction
Creator: Dr. Brian Staiger, PharmD, BCPS

A pharmacist-reviewed analysis of the Bisacodyl Rectal and Magnesium Hydroxide interaction: the documented clinical effects, severity rating, onset, mechanism, and management considerations, with cited references throughout.

AI-assisted, pharmacist-reviewed · Source data updated Aug 8, 2026 · Sources: FDA labeling, DDInter 2.0, cited literature

Magnesium Hydroxide

Almacone® (containing Aluminum Hydroxide, Magnesium Hydroxide, Simethicone) Alumox® (containing Aluminum Hydroxide, Magnesium Hydroxide, Simethicone) ConRX® AR (containing Aluminum Hydroxide, Magnesium Hydroxide) Duo Fusion® (containing Calcium Carbonate, Famotidine, Magnesium Hydroxide) Milk of Magnesia® Mirafast Pedia-Lax Chewable Pedia-Lax®

Bisacodyl Rectal

Bisac-Evac Bisac-Evac® Suppositories Bisacodyl Uniserts® Dulcolax Dulcolax® Suppositories Fleet® Bisacodyl Enema The Magic Bullet

Medically reviewed by

Dr. Brian Staiger, PharmD, BCPS

Updated Aug 8, 2026

Editorial policy · Data sources

Interaction severity

Minor

Usually limited clinical impact.

Minor

Moderate

Major

Contraindicated

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.

Of 18 documented Bisacodyl Rectal interactions, 15 are rated minor — including this one.

Onset

rapid

Evidence

theoretical

Severity

Minor

What happens

Decreased effectiveness of bisacodyl

Interaction Deep Dive

Bisacodyl should not be given within one hour of an antacid¹.

Why it happens (mechanism)

Unknown

Common questions

Can I take Bisacodyl Rectal and Magnesium Hydroxide together?

Decreased effectiveness of bisacodyl Always confirm with your pharmacist or prescriber before making any change.

How serious is the Bisacodyl Rectal and Magnesium Hydroxide 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 strong is the evidence for this interaction?

The evidence is graded "theoretical". Predicted from the drugs' pharmacology; not yet confirmed in people.

Questions for your pharmacist

Does my dose of Bisacodyl Rectal or Magnesium Hydroxide 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 (1)

Product Information: Dulcolax(R), bisacodyl. Boehringer Ingelheim Pharmaceuticals, Ridgefield, CT, 1993. DailyMed

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Magnesium Hydroxide

Keep reading about Magnesium Hydroxide

All Magnesium Hydroxide interactions (53) Magnesium Hydroxide drug information

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Bisacodyl Rectal

Keep reading about Bisacodyl Rectal

All Bisacodyl Rectal interactions (18) Bisacodyl Rectal drug information

Also serious with: Licorice Magnesium Sulfate Polyethylene Glycol 3350

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HelloPharmacist doesn't license one of the big commercial interaction databases, so what you'll find here is not a complete list of every known drug interaction. Instead, each entry is researched, analyzed, and written up individually — documented from the published literature, reviewed by a pharmacist, and cited so you can check every source yourself.

If a combination isn't listed here, it means we haven't documented it yet — never that it's safe. For screening a full medication list, we recommend pairing this site with a comprehensive tool like the Drugs.com Interaction Checker and, most importantly, a review by your own pharmacist. For a deep, plain-English, fully sourced explanation of a specific documented interaction — that's exactly what we built this for.

This information is for education, not a substitute for professional medical advice. Do not start, stop, or change any medication without talking to your pharmacist or prescriber.