Drug & supplement interaction

Magnesium + Selumetinib Sulfate

Selumetinib Sulfate brand name: Koselugo.

Minor Interaction
Medically reviewed by · Updated September 2026
The bottom line Minor

Magnesium has a minor interaction with Selumetinib Sulfate. Theoretically, magnesium may have antiplatelet effects, but the evidence is conflicting.

Read the full interaction report
SeverityMinor
LikelihoodUnlikely
EvidenceB
What do Severity, Likelihood & Evidence mean?
Know someone taking this? Share
Facebook Post Reddit Email
On this page
Interaction report

Magnesium and Selumetinib Sulfate

Here is the interaction we found between these two, with the evidence behind it.

Minor

ANTICOAGULANT/ANTIPLATELET DRUGS

Why this applies to Selumetinib Sulfate

Selumetinib Sulfate falls under ANTICOAGULANT/ANTIPLATELET DRUGS — the group Magnesium interacts with.

Theoretically, magnesium may have antiplatelet effects, but the evidence is conflicting.
In vitro evidence shows that magnesium sulfate inhibits platelet aggregation, even at low concentrations. Some preliminary clinical evidence shows that infusion of magnesium sulfate increases bleeding time by 48% and reduces platelet activity. However, other clinical research shows that magnesium does not affect platelet aggregation, although inhibition of platelet-dependent thrombosis can occur.
Severity Minor Likelihood Unlikely Evidence B

Interaction has been demonstrated in animal or in lab research but has been shown not to occur in humans..

Dr. Brian Staiger, PharmD, BCPS
Dr. Brian Staiger explains PharmD, Clinical Pharmacist

Here's the honest picture for combining magnesium with Koselugo (selumetinib). The interaction on file isn't really about how selumetinib is broken down. Instead, it comes from a theoretical idea that magnesium might gently slow down platelets (the cells that help your blood clot). The evidence for that is weak and mixed, with some studies showing a small effect and others showing none at all.

What does this mean in practice? Very little for most people. If your child is taking selumetinib and you're using magnesium at normal supplement amounts, the chance of a real bleeding problem is low. Still, if you ever notice easy bruising, nosebleeds, or bleeding that's slow to stop, mention it to your doctor or pharmacist before changing anything.

Contact Dr. Brian directly if you have additional questions on this interaction
References
  1. Ravn HB, Vissinger H, Kristensen SD, et al. Magnesium inhibits platelet activity--an in vitro study. Thromb Haemost. 1996;76(1):88-93. DOI
  2. Ravn HB, Kristensen SD, Vissinger H, et al. Magnesium inhibits human platelets. Blood Coagul Fibrinolysis. 1996;7(2):241-4. PubMed
  3. Ravn HB, Vissinger H, Kristensen SD, et al. Magnesium inhibits platelet activity--an infusion study in healthy volunteers. Thromb Haemost. 1996;75(6):939-44. DOI
  4. Shechter, M., Merz, C. N., Paul-Labrador, M., Meisel, S. R., Rude, R. K., Molloy, M. D., Dwyer, J. H., Shah, P. K., and Kaul, S. Beneficial antithrombotic effects of the association of pharmacological oral magnesium therapy with aspirin in coronary heart

What These Ratings Mean

Every interaction above is graded three ways — here’s the key to each label.

Severity how clinically significant the interaction is
Major

Clinically significant. Avoid the combination, or use only under close professional supervision.

Moderate

Usually worth avoiding or managing — may need monitoring, a dose change, or timing apart.

Minor

Generally not serious. Be aware of it and mention it to your pharmacist.

Likelihood how strong the evidence is that the interaction actually happens in people
  • LikelyWell-controlled human studies have demonstrated the likely existence of this interaction.
  • ProbableInteraction has not been documented in well-controlled studies, however, the interaction has been demonstrated in some small human studies or in controlled animal studies in conjunction with multiple case reports.
  • PossibleInteraction has been documented in animal or in lab research, or the interaction has been documented in humans but is limited to case reports or conflicting clinical research exists.
  • UnlikelyInteraction has been demonstrated in animal or in lab research but has been shown not to occur in humans.
Evidence the quality of the studies behind the rating (graded A–D)
  • AHigh-quality meta-analysis (quantitative systematic review).
  • BCase-control study.
  • CConsensus.
  • DAnecdotal evidence.

These ratings are for information only. Never start, stop, or otherwise change your therapy before speaking with your provider.

Keep it in perspective

Magnesium Also Interacts With Other Medications

Magnesium has 6 major, 175 moderate, 113 minor known drug interactions in our database — the Selumetinib Sulfate one above is one of them. If you take anything else, check it against the full list below.

Major 6 Moderate 175 Minor 113 No known interaction 2,536 (incl. Selumetinib Sulfate)
Taking anything else?

Check Another of Your Medications Against Magnesium

Covers the 2,830 medications we’ve checked against Magnesium. Pick one to open its full report.

From our Q&A

Questions About Magnesium or Selumetinib Sulfate

These are real questions from readers, answered by the pharmacists at HelloPharmacist — written by a person, not generated from a database. Each one covers Magnesium or Selumetinib Sulfate, not necessarily both, but if one is close to what you were about to ask it will usually go further than a database entry can:

Not quite your question? Ask our pharmacists directly — it is free, there is no account required, and answers usually come back within 24 hours.

Everything else you take

See Every Supplement That Interacts With Selumetinib Sulfate

This page covers Magnesium only. If you take other supplements — a multivitamin, a sleep aid, something for joints — the Selumetinib Sulfate page lists 282 supplements it has a documented interaction with, worst first, each one explained.

The most serious there right now: Activated Charcoal (major), Danshen (major), Grapefruit (major), Piracetam (major) and St. John's Wort (major).

By severity: 5 major · 236 moderate · 41 minor.

Open the Selumetinib Sulfate interaction page

One more smart check

Taking Magnesium as Part of a Dietary Supplement Product? Check It for Interactions

We hold 29,717 real supplement products containing Magnesium, each one broken down to its full ingredient list — and combination products often carry several ingredients besides Magnesium. Your product may carry other ingredients that interact with Selumetinib Sulfate too, on top of Magnesium — and those would not show on this page. Find your product and we’ll check every ingredient on its label:

How much people look this up

Where Magnesium and Selumetinib Sulfate Sit Against Everything Else

Out of every supplement and medication people look up on HelloPharmacist, here is where these two land this week — and which way each has been moving.

Supplement Magnesium
Top 10

#4 of 1,452 supplements looked up here in the last 7 days

29 days ago today
Medication Selumetinib Sulfate
Steady interest

#2,176 of 2,830 medications looked up here in the last 7 days

29 days ago today

Position among everything looked up on this site, not a measure of how commonly either one is used or how important it is. A supplement can climb this list because of a news story. It counts every request to the page, automated ones included, and nothing here identifies anyone.

Supplement

About Magnesium

What is Magnesium?

Magnesium
  • Preventing or treating magnesium deficiency
  • Constipation
  • Muscle cramps
  • Sleep support
  • Anxiety and stress
  • Migraine prevention

Magnesium is an essential mineral your body needs for muscles, nerves, blood pressure, and many other functions, and supplements are useful for preventing or correcting deficiency. Some other uses, like easing constipation or preventing migraines, have reasonable support, while uses for sleep and anxiety are less proven. It is generally safe for most healthy people at recommended amounts, but talk to your pharmacist or doctor before starting, especially if you have kidney problems.

Read the full Magnesium monograph & all interactions
Medication

About Selumetinib

What Is Selumetinib Used For?

Brand name: Koselugo

Koselugo (selumetinib) is approved for adults and children 1 year of age and older who have neurofibromatosis type 1 (NF1) — a genetic condition that causes tumors to grow on nerve tissue — when they also have symptomatic, inoperable plexiform neurofibromas (large, deep nerve tumors that cannot be surgically removed and are causing problems).

Both the Koselugo capsule and Koselugo oral granule formulations are approved for this use. The oral granule form is intended for patients who have difficulty swallowing whole capsules.

See full Selumetinib drug information
Keep checking

Other Drugs & Magnesium

Browse every other medication we’ve checked against Magnesium — both the ones with a known interaction and the ones without. Select any drug for the full detail.

6Major
175Moderate
113Minor
2,535No known interaction
6 Major 175 Moderate 113 Minor 2,535 No interaction
Major

6 interactions

Moderate

175 interactions

Showing 60 of 175 moderate interactions — see all 175 on the Magnesium page.

Minor

113 interactions

Showing 60 of 113 minor interactions — see all 113 on the Magnesium page.

No interaction 2,535 drugs checked — show the list

We also checked Magnesium against these medications and found no known interaction in our sources. Open any page to confirm.

Showing the 60 most looked-up of 2,535 medications checked with no known interaction — see the full Magnesium list.

See the full Magnesium interactions page
See every supplement checked against Selumetinib Sulfate, ranked by severity
Sources

Sources & How We Checked

Interaction details are evidence-graded and sourced from the Natural Medicines database. The medication overview comes from MedlinePlus.

Content is written and reviewed by licensed HelloPharmacist pharmacists. See our data sources and editorial standards for how this information is built and checked.

Parts of this content are provided by the Therapeutic Research Center, LLC.

DISCLAIMER: Currently this does not check for drug-drug interactions. This is not an all-inclusive comprehensive list of potential interactions and is for informational purposes only. Not all interactions are known or well-reported in the scientific literature, and new interactions are continually being reported. Input is needed from a qualified healthcare provider including a pharmacist before starting any therapy. Application of clinical judgment is necessary.

© 2021 Therapeutic Research Center, LLC

Keep exploring
Magnesium monograph › Uses, safety, and every drug interaction in one place Selumetinib Sulfate supplement interactions › Every supplement checked against Selumetinib Sulfate, ranked by severity Selumetinib drug information › The full plain-English guide to this medication Supplement interaction checker › Check any supplement or product against your medications Browse medications A–Z › Every drug we've checked against herbs & supplements Ask a pharmacist › Free, personal answer from our licensed team
Pharmacist Counseling Corner

Taking Magnesium and Selumetinib Sulfate Together: Common Questions

Can you take Magnesium with Selumetinib Sulfate?
There is only a minor interaction, which is usually not serious. Read the full details on this page and confirm with your pharmacist before combining them.
How serious is the Magnesium and Selumetinib Sulfate interaction?
We rate it Minor. This interaction is generally not clinically significant, but it remains worth noting and discussing with your pharmacist.

Written and reviewed by the HelloPharmacist editorial staff. Our editorial policy

Still Have a Question About Selumetinib Sulfate and Magnesium?

Our pharmacists answer your medication & supplement questions — free.

Ask a pharmacist

This information is for education only and is not a substitute for professional medical advice. Always check with your pharmacist or doctor before starting, stopping, or combining supplements and medications.