Drug & supplement interaction

Cesium + Hydroxychloroquine

Hydroxychloroquine brand name: Plaquenil.

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

Cesium has a major interaction with Hydroxychloroquine. Theoretically, taking cesium concomitantly with other drugs that prolong the QT interval may increase the risk of ventricular arrhythmias and death.

Read the full interaction report
SeverityMajor
LikelihoodProbable
EvidenceD
What do Severity, Likelihood & Evidence mean?
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Interaction report

Cesium and Hydroxychloroquine

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

Major

QT INTERVAL-PROLONGING DRUGS

Why this applies to Hydroxychloroquine

Hydroxychloroquine falls under QT INTERVAL-PROLONGING DRUGS — the group Cesium interacts with.

Theoretically, taking cesium concomitantly with other drugs that prolong the QT interval may increase the risk of ventricular arrhythmias and death.
Taking cesium can prolong the QT interval on electrocardiogram (ECG). In many cases, cesium-induced QT prolongation has led to serious adverse effects, including torsades de pointes, cardiac arrest, and death.
Severity Major Likelihood Probable Evidence D

Interaction 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..

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

Here's the concern with combining cesium and hydroxychloroquine (Plaquenil). Hydroxychloroquine is one of those medicines that can lengthen the heart's electrical reset time, what we call the QT interval. Cesium chloride does the very same thing, and on its own it has been linked to dangerous rhythm disturbances, including a rhythm called torsades de pointes, cardiac arrest, and even death.

Stacking two QT-stretching agents together raises the odds of fainting, a racing or irregular heartbeat, or a sudden serious arrhythmia. Honestly, cesium is not a safe or proven supplement to begin with, so I'd steer clear of it entirely. Please talk with your doctor or pharmacist before pairing anything new with your hydroxychloroquine.

Contact Dr. Brian directly if you have additional questions on this interaction
References
  1. Lyon AW, Mayhew WJ. Cesium toxicity: A case of self-treatment by alternate therapy gone awry. Ther Drug Monit 2003;25:114-6. PubMed
  2. Vyas H, Johnson K, Houlihan R, et al. Acquired long QT syndrome secondary to cesium chloride supplement. J Altern Complement Med 2006;12:1011-4. PubMed
  3. Pinter A, Dorian P, Newman D. Cesium-induced torsades de pointes. N Engl J Med 2002;346:383-4. PubMed
  4. O'Brien CE, Harik N, James LP, et al. Cesium-induced QT-interval prolongation in an adolescent. Pharmacotherapy 2008;28:1059-65. PubMed
  5. FDA alerts health care professionals of significant safety risks associated with cesium chloride. FDA: Human Drug Compounding. July 23,2018. Available at: https://www.fda.gov/drugs/human-drug-compounding/fda-alerts-health-care-professionals-significant-sa
  6. Public Health Alert Concerning Dietary Supplements Containing Cesium Salts. FDA Dietary Supplement Products & Ingredients. February 5, 2020. Available at: https://www.fda.gov/food/dietary-supplement-products-ingredients/public-health-alert-concerning-diet

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

Cesium Also Interacts With Other Medications

Cesium has 160 major, 94 moderate known drug interactions in our database — the Hydroxychloroquine one above is one of them. If you take anything else, check it against the full list below.

Major 160 Moderate 94 No known interaction 2,576 (incl. Hydroxychloroquine)
Taking anything else?

Check Another of Your Medications Against Cesium

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

From our Q&A

Questions About Cesium or Hydroxychloroquine

These are real questions from readers, answered by the pharmacists at HelloPharmacist — written by a person, not generated from a database. Each one covers Cesium or Hydroxychloroquine, 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 Hydroxychloroquine

This page covers Cesium only. If you take other supplements — a multivitamin, a sleep aid, something for joints — the Hydroxychloroquine page lists 32 supplements it has a documented interaction with, worst first, each one explained.

The most serious there right now: Activated Charcoal (major), American Hellebore (major), Arsenic (major), Ephedra (major) and Grapefruit (major).

By severity: 7 major · 16 moderate · 9 minor.

From our pharmacist’s overview on the Hydroxychloroquine page

“Hydroxychloroquine (Plaquenil) can stretch the QT interval on its own, the pause between heartbeats that, prolonged too far, can trigger a dangerous rhythm. Thirteen of the supplements and herbs on this page add to that same effect, grapefruit in large amounts among them, and that overlap is why this list calls for genuine care rather…”

Reviewed by 2 · Jul 18, 2026

Open the Hydroxychloroquine interaction page

One more smart check

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

We hold 51 real supplement products containing Cesium, each one broken down to its full ingredient list — and combination products often carry several ingredients besides Cesium. Your product may carry other ingredients that interact with Hydroxychloroquine too, on top of Cesium — 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 Cesium and Hydroxychloroquine 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 Cesium
Steady interest

#1,013 of 1,452 supplements looked up here in the last 7 days

29 days ago today
Medication Hydroxychloroquine
Top 25%

#359 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 Cesium

What is Cesium?

  • Marketed as an alternative cancer treatment ('high pH therapy')
  • Claimed to alter tumor pH
  • General 'alkaline' health claims

Cesium chloride is a mineral salt sold as an alternative cancer therapy ('high pH therapy'), but there is no reliable scientific evidence that it treats cancer or any other disease. It can cause dangerous heart rhythm problems and even death, so it should not be used. Talk to your doctor or pharmacist before taking any supplement, and never use cesium in place of proven medical care.

Read the full Cesium monograph & all interactions
Medication

About Hydroxychloroquine

What Is Hydroxychloroquine Used For?

Brand name: Plaquenil

Hydroxychloroquine tablets are used to treat uncomplicated malaria and to help prevent malaria in areas where the parasite has not developed resistance to it — in both adults and children. It is also used in adults to treat rheumatoid arthritis, systemic lupus erythematosus (SLE), and chronic discoid lupus erythematosus.

There are important limits: it is not recommended for complicated or drug-resistant malaria, malaria acquired in regions where resistance is known, or to prevent malaria relapses caused by P. vivax or P. ovale. Its use for the autoimmune conditions (rheumatoid arthritis and lupus) is approved for adults only.

See full Hydroxychloroquine drug information
Keep checking

Other Drugs & Cesium

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

160Major
94Moderate
0Minor
2,575No known interaction
160 Major 94 Moderate 2,575 No interaction
Major

160 interactions

Showing 60 of 160 major interactions — see all 160 on the Cesium page.

Moderate

94 interactions

Showing 60 of 94 moderate interactions — see all 94 on the Cesium page.

No interaction 2,575 drugs checked — show the list

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

Showing the 60 most looked-up of 2,575 medications checked with no known interaction — see the full Cesium list.

See the full Cesium interactions page
See every supplement checked against Hydroxychloroquine, 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
Cesium monograph › Uses, safety, and every drug interaction in one place Hydroxychloroquine supplement interactions › Every supplement checked against Hydroxychloroquine, ranked by severity Hydroxychloroquine 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 Cesium and Hydroxychloroquine Together: Common Questions

Can you take Cesium with Hydroxychloroquine?
This is rated a major interaction, so the combination is best avoided unless your doctor or pharmacist has specifically told you otherwise. Read the full details on this page and confirm with your pharmacist before combining them.
How serious is the Cesium and Hydroxychloroquine interaction?
We rate it Major. This is a clinically significant combination that is generally best avoided, or used only under the direct supervision of your physician or pharmacist.

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

Still Have a Question About Hydroxychloroquine and Cesium?

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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.