Ascophyllum Nodosum + Methenamine Mandelate
Methenamine Mandelate brand names: Mandelamine, Methimazole.
Ascophyllum Nodosum has a moderate interaction with Methenamine Mandelate. Due to its iodine content, Ascophyllum nodosum might alter the effects of antithyroid drugs.
Read the full interaction reportAscophyllum Nodosum and Methenamine Mandelate
Here is the interaction we found between these two, with the evidence behind it.
ANTITHYROID DRUGS
Why this applies to Methenamine Mandelate
Methenamine Mandelate falls under ANTITHYROID DRUGS — the group Ascophyllum Nodosum interacts with.
Ascophyllum nodosum contains iodine, although the bioavailability of iodine from Ascophyllum nodosum is lower than that of potassium iodide. Iodine in high doses has been reported to cause both hyperthyroidism and hypothyroidism, depending on the individual's past medical history. Taking Ascophyllum nodosum while using antithyroid drugs could alter the effects of the antithyroid drugs.
Interaction 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.
Quick heads-up on the drug names here: the brand info lists methimazole, which is an antithyroid medicine you take when your thyroid is overactive. The whole point of that pill is to dial down how much thyroid hormone your body makes. Bladderwrack (Ascophyllum nodosum) is naturally loaded with iodine, and iodine is the raw material your thyroid uses to build hormone. So adding an iodine source while you're trying to calm the thyroid can work against your medicine.
This is a theoretical concern based on how iodine behaves, not proven harm, and the iodine from this seaweed is absorbed less than from plain iodide. Still, the amount in supplements is hard to predict and could nudge your levels either way, possibly making you feel jittery, hot, or shaky again. Please check with your pharmacist or doctor before combining them.
- Sterling JB, Heymann WR. Potassium iodide in dermatology: a 19th century drug for the 21st century-uses, pharmacology, adverse effects, and contraindications. J Am Acad Dermatol 2000;43:691-7. PubMed
- Combet E, Ma ZF, Cousins F, et al. Low-level seaweed supplementation improves iodine status in iodine-insufficient women. Br J Nutr 2014;112:753-61. PubMed
- Simmons-Boyce JL, Purcell SL, Nelson CM, MacKinnon SL. Dietary Ascophyllum nodosum increases urinary excretion of tricarboxylic acid cycle intermediates in male Sprague-dawley rats. J Nutr 2009;139:1487-94. PubMed
- Sorge US, Henriksen M, Bastan A, et al. Short communication: Iodine concentrations in serum, milk, and tears after feeding Ascophyllum nodosum to dairy cows-A pilot study. J Dairy Sci 2016;99:8472-6. PubMed
What These Ratings Mean
Every interaction above is graded three ways — here’s the key to each label.
Clinically significant. Avoid the combination, or use only under close professional supervision.
Usually worth avoiding or managing — may need monitoring, a dose change, or timing apart.
Generally not serious. Be aware of it and mention it to your pharmacist.
- 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.
- 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.
Ascophyllum Nodosum Also Interacts With Other Medications
Ascophyllum Nodosum has 21 moderate known drug interactions in our database — the Methenamine Mandelate one above is one of them. If you take anything else, check it against the full list below.
Check Another of Your Medications Against Ascophyllum Nodosum
We haven’t checked that one against Ascophyllum Nodosum yet — ask our pharmacists directly.
Covers the 2,830 medications we’ve checked against Ascophyllum Nodosum. Pick one to open its full report.
See Every Supplement That Interacts With Methenamine Mandelate
This page covers Ascophyllum Nodosum only. If you take other supplements — a multivitamin, a sleep aid, something for joints — the Methenamine Mandelate page lists 91 supplements it has a documented interaction with, worst first, each one explained.
The most serious there right now: Activated Charcoal (major), Beer (major), Siberian Cocklebur (major), Wine (major) and Ashwagandha (moderate).
By severity: 4 major · 77 moderate · 10 minor.
From our pharmacist’s overview on the Methenamine Mandelate page
“People take methenamine mandelate (Mandelamine) day after day to keep urinary tract infections at bay, and that long habit is exactly why the 91 supplements on this page deserve genuine vigilance. Four carry a major rating, and most of those point at the liver: Siberian cocklebur has been linked to outright liver failure, and heavy bee…”
Reviewed by 2 · Jul 18, 2026
Taking Ascophyllum Nodosum as Part of a Dietary Supplement Product? Check It for Interactions
We hold 360 real supplement products containing Ascophyllum Nodosum, each one broken down to its full ingredient list — and combination products often carry several ingredients besides Ascophyllum Nodosum. Your product may carry other ingredients that interact with Methenamine Mandelate too, on top of Ascophyllum Nodosum — and those would not show on this page. Find your product and we’ll check every ingredient on its label:
Where Ascophyllum Nodosum and Methenamine Mandelate 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.
#333 of 1,452 supplements looked up here in the last 7 days
#2,285 of 2,830 medications looked up here in the last 7 days
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.
About Ascophyllum Nodosum
What is Ascophyllum Nodosum?
- Weight management
- Blood sugar support
- Thyroid support (iodine source)
- Digestive health
- Source of vitamins and minerals
- Joint comfort
Ascophyllum nodosum (often sold as bladderwrack or brown seaweed) is a nutrient-rich algae that people use for weight, blood sugar, and thyroid support, but solid human evidence is limited for most of these uses. Because it naturally contains iodine and can absorb heavy metals like arsenic, it should be used cautiously, and pregnant or breastfeeding people should avoid it unless a doctor approves.
About Methimazole
What Is Methimazole Used For?
Brand names: Mandelamine, Methimazole
Methimazole tablets treat hyperthyroidism in people with Graves’ disease or toxic multinodular goiter (a enlarged thyroid with overactive lumps). They are used when surgery or radioactive iodine is not a suitable option.
They are also used to ease hyperthyroid symptoms while a person gets ready for thyroidectomy (thyroid removal surgery) or radioactive iodine therapy.
Other Drugs & Ascophyllum Nodosum
Browse every other medication we’ve checked against Ascophyllum Nodosum — both the ones with a known interaction and the ones without. Select any drug for the full detail.
No drugs match “”.
21 interactions
- Levothyroxine ›
- Conjugated Estrogens ›
- Testosterone Undecanoate ›
- Levothyroxine Sodium ›
- Liotrix ›
- Amiodarone ›
- Desiccated Thyroid Extract ›
- Desiccated Thyroid Extract (prescription Drug) ›
- Menotropins ›
- Carbimazole ›
- Dextrothyroxine ›
- Human Chorionic Gonadotropin (hcg) ›
- Liothyronine ›
- Methimazole ›
- Ospemifene ›
- Potassium Iodide (prescription Drug) ›
- Thyroglobulin ›
- Thyroid Hormone ›
- Levothyroxine, Liothyronine ›
- Liotrix, T4/t3 ›
- Propylthiouracil, Ptu ›
No interaction 2,808 drugs checked — show the list
We also checked Ascophyllum Nodosum against these medications and found no known interaction in our sources. Open any page to confirm.
- Apixaban ›
- Amlodipine ›
- Warfarin ›
- Methylphenidate ›
- Ivermectin ›
- Abemaciclib ›
- Rosuvastatin ›
- Sertraline ›
- Losartan Potassium ›
- Acetaminophen ›
- Testosterone ›
- Aspirin ›
- Clopidogrel ›
- Metoprolol ›
- Escitalopram ›
- Atorvastatin ›
- Rivaroxaban ›
- Warfarin Sodium ›
- Ibuprofen ›
- Tirzepatide ›
- Isotretinoin ›
- Metformin ›
- Docusate ›
- Tadalafil ›
- Amlodipine Besylate ›
- Prednisone ›
- Propranolol ›
- Amitriptyline ›
- Amphetamine ›
- Semaglutide ›
- Lisdexamfetamine ›
- Methamphetamine ›
- Sumatriptan ›
- Amoxicillin ›
- Lisinopril ›
- Valacyclovir ›
- Hydroxyurea ›
- Bupropion ›
- Fluoxetine ›
- Methotrexate ›
- Azithromycin ›
- Doxycycline ›
- Pregabalin ›
- Gabapentin ›
- Acetaminophen, Aspirin, Caffeine ›
- Clonazepam ›
- Naproxen ›
- Lamotrigine ›
- Buspirone ›
- Quetiapine ›
- Dextroamphetamine ›
- Acyclovir ›
- Omeprazole ›
- Duloxetine ›
- Letrozole ›
- Methylene Blue ›
- Citalopram ›
- Bendamustine ›
- Ciprofloxacin ›
- Acetaminophen, Butalbital, Caffeine ›
Showing the 60 most looked-up of 2,808 medications checked with no known interaction — see the full Ascophyllum Nodosum list.
Sources & How We Checked
Interaction details are evidence-graded and sourced from the Natural Medicines database. The medication overview comes from MedlinePlus.
- Natural Medicines (Therapeutic Research Center) — Evidence-graded clinical reference for vitamins, herbs and supplements — the basis for our interaction data.
- MedlinePlus, U.S. National Library of Medicine — NIH consumer drug information, used for the medication overviews.
- NIH Dietary Supplement Label Database (DSLD) — Official supplement product labels.
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
Methenamine Mandelate Is Linked to Lower Levels of 7 Nutrients
Natural Medicines records Methenamine Mandelate as a medicine that can lower these. This is not an interaction with Ascophyllum Nodosum — it is a separate effect of the medicine, and it is a reason some people are advised to supplement rather than to avoid one:
Read the full Methenamine Mandelate nutrient depletion report ›
Depletion records come from the licensed Natural Medicines database. Do not start a supplement on the strength of this page — ask your pharmacist or doctor whether it applies to you.
Taking Ascophyllum Nodosum and Methenamine Mandelate Together: Common Questions
Can you take Ascophyllum Nodosum with Methenamine Mandelate?
How serious is the Ascophyllum Nodosum and Methenamine Mandelate interaction?
Written and reviewed by the HelloPharmacist editorial staff. Our editorial policy
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