The short answer
Evidence does not establish a general magnesium supplement interaction with valproate. Older studies tested particular antacids and gave differing absorption results, so review the exact products with your pharmacist.
What this answer covers
Oral magnesium supplements distinguished from multi-ingredient antacids and from magnesium valproate, a medication salt. Historical Maalox preparations cannot be assumed identical to current Maalox Plus or to an isolated magnesium salt.
- Supplement or preparation
- Magnesium
- Medication ingredient
- valproate
What the older antacid study found
In seven healthy volunteers, an original study reported a small increase in total valproic acid exposure with Maalox, but not a significant increase with the other two antacids. The current valproic acid label summarizes the antacid study as showing no change in the extent of absorption. This discrepancy prevents a simple universal conclusion.
Rate and total absorption can differ
A separate study in nine healthy adults found that Maalox delayed absorption of sodium valproate syrup without significantly changing total exposure. It used a particular syrup and antacid, and did not measure seizure control. Such a result cannot establish that a nutritional magnesium supplement makes valproate work better or worse.
Identify the exact products
Current Maalox Plus contains magnesium hydroxide together with aluminium hydroxide and simeticone. It is not proven identical to the older study products. A mixed-antacid result cannot be assigned to magnesium alone; magnesium valproate is a form of the prescribed medicine, not a magnesium supplement.
Ask about timing for your formulation
Give the pharmacist both product labels, including whether valproate is a syrup, capsule or modified-release product. Follow any product-specific antacid instructions. The evidence does not establish one valproate-specific spacing rule for all magnesium products, and you should not alter the valproate dose yourself.
Evidence and practical considerations
Absorption & effectiveness
A broad effect of magnesium supplements on valproate absorption or clinical effectiveness is not established. Small commercial-antacid studies have formulation-specific, inconsistent pharmacokinetic findings.
- Exact scope
- Oral magnesium supplements distinguished from multi-ingredient antacids and from magnesium valproate, a medication salt. Historical Maalox preparations cannot be assumed identical to current Maalox Plus or to an isolated magnesium salt. with Valproate RxCUI 40254 IN. NLM identifies valproic acid and sodium valproate as related precise ingredients; oral valproic acid dissociates to valproate. This active-moiety bridge does not equate release kinetics, all salts, doses or routes.
- Medication form and route
- Oral
What remains uncertain
- Historical antacid compositions were not independently established from the inspected original bodies; no isolated-magnesium arm or seizure outcome was demonstrated. The label and 1982 abstract differ on total exposure.
Factors that may matter: Exact preparation and route; Age and clinical indication; Baseline nutritional status; Other treatments.
Read the supporting source summaries
Source 1: Current U.S. prescribing information
dailymed.nlm.nih.gov · Source check Sep 10, 2026
Population: Patients receiving oral valproic acid.
Recommends folic acid before conception and during pregnancy for women of childbearing potential. Protection against valproate-associated neural tube defects or reduced IQ is unknown. Warns of hyperammonemia and abrupt discontinuation. States no extent-of-absorption effect in the specified antacid study.
How this applies: Exact active-moiety safety and formulation-specific context. Valproate RxCUI 40254 IN. NLM identifies valproic acid and sodium valproate as related precise ingredients; oral valproic acid dissociates to valproate. This active-moiety bridge does not equate release kinetics, all salts, doses or routes.
Not proof of universal nutrient deficiency or of an interaction with each supplement. The antacid summary differs from the original 1982 abstract; that difference is retained.
Source 2: Original clinical research
ebi.ac.uk · Source check Sep 10, 2026
Population: Seven healthy volunteers.
Maalox increased total AUC by a mean 12%, range 3-28%; the other products showed nonsignificant trends. Peak, time-to-peak and elimination measures did not differ.
How this applies: Indirect commercial-antacid evidence. Cannot assign a mixture response to magnesium alone.
Original abstract only; historical product composition not independently established from the body. No isolated magnesium arm, seizure endpoint or universal supplement equivalence. Current valproic acid labeling summarizes the antacid exposure differently.
Source 3: Original clinical research
jstage.jst.go.jp · Source check Sep 10, 2026
Population: Nine healthy adults, seven men and two women, age 35-51.
Maalox delayed absorption rate without a significant difference in total exposure.
How this applies: Indirect antacid co-use evidence with an explicit sodium-valproate syrup boundary; not evidence for all magnesium salts or release formulations.
English abstract states 20 mL Maalox, whereas Japanese methods state 30 mL. Historical product composition is not fully specified. Small single-dose study, no seizure-control endpoint and no isolated magnesium exposure.
Source 4: Current combination-antacid product information
medicines.org.uk · Source check Sep 10, 2026
Population: Users of the current UK Maalox Plus oral suspension.
Identifies multiple active ingredients and gives general oral-medicine separation precautions.
How this applies: Establishes a current magnesium-containing antacid example and why mixture effects cannot be attributed to magnesium alone.
This current product is not proven identical to the historical Maalox products in the two trials. General antacid spacing instructions are not evidence of a valproate-specific benefit or a rule for all magnesium supplements.
Source 5: Authoritative medication terminology
rxnav.nlm.nih.gov · Source check Sep 10, 2026
Population: Medication terminology, not clinical participants.
Identifies valproate as IN and calcium valproate, magnesium valproate, valproic acid, sodium valproate and divalproex sodium as related PIN concepts.
How this applies: Supports exact medication identity and exclusion of medication salts from supplement exposure.
Terminology relationships do not establish bioequivalence, equal release kinetics, supplemental mineral exposure or a clinical interaction.
Research assessment: · Open full citations ↗
Review and change history
- Publication status
- Published research summary
- Clinical review
- Not yet recorded
| Date | Update |
|---|---|
| Article prepared | |
| Sources checked and article drafted. | |
| Research summary published |
Article revision: 49392efa01146afe
This guide brings together the evidence records used by our interaction checker. Each finding retains its own preparation limits, research date, and source summaries.
Full citations require verification. Reading this answer and the source summaries does not.
Taking other supplements or medications?
Use the checker to explore your other combinations. Ask a pharmacist to review the exact products, amounts and medical conditions in your complete list.
Open the interaction checkerInformation, not medical advice. Do not change prescribed treatment based on this guide.