Ascophyllum Nodosum - Premarin (Conjugated Estrogens) Interaction
Herbal: Ascophyllum Nodosum
Also Known As: Bladderwrack, Brown Marine Algae, Brown seaweed, Egg Wrack, Hebridean Seaweed, ID-alG, Irish Brown Seaweed, Kelp, Knotted Wrack, Norwegian Kelp, Rockweed, Tasco
Drug: Conjugated Estrogens
Brand names:
Premarin, Cenestin, Enjuvia, Premarin Vaginal Cream
Medical Content Editor Dr. Brian Staiger, PharmD
Last updated
May 11, 2025
Interaction Details
Conjugated Estrogens is classified as belonging to the following category: Thyroid Hormone
Due to its iodine content, Ascophyllum nodosum might alter the effects of thyroid hormone.
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 thyroid hormone could alter the effects of thyroid hormone.
Interaction Rating
Likelihood of Occurrence
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
References
- 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.
- 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.
- 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.
- 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.
Ascophyllum Nodosum Overview
Ascophyllum nodosum is a species of brown seaweed that inhabits the shorelines of various regions including the Canadian Arctic, Greenland, Iceland, Europe, the northeastern United States, and the eastern coast of Canada. In many areas, this seaweed has become a protected species in an effort to prevent overharvesting. Ascophyllum nodosum boasts a rich nutrient profile, containing polysaccharides like fucoidans and laminarin, and an array of vitamins and minerals, including iodine. Furthermore, this seaweed is notable for carrying phlorotannins, a substance found exclusively in brown seaweed, as well as a variety of fatty acids. These include oleic acid, saturated fatty acids and polyunsaturated fatty acids of both the omega-3 and omega-6 varieties.
Conjugated Estrogens Overview
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The estradiol cypionate and estradiol valerate forms of estrogen injection are used to treat hot flushes (hot flashes; sudden strong feelings of heat and sweating) and/or vaginal dryness, itching, and burning in women who are experiencing menopause (change of life; the end of monthly menstrual periods). However, women who need a medication only to treat vaginal dryness, itching, or burning should consider a different treatment. These forms of estrogen injection are also sometimes used to treat the symptoms of low estrogen in young women who do not produce enough estrogen naturally. The estradiol valerate form of estrogen injection is also sometimes used to relieve the symptoms of certain types of prostate (a male reproductive organ) cancer. The conjugated estrogens form of estrogen injection is used to treat abnormal vaginal bleeding that a doctor has decided is caused only by a problem with the amounts of certain hormones in the body. Estrogen injection is in a class of medications called hormones. It works by replacing estrogen that is normally produced by the body.
Ascophyllum Nodosum - More Interactions
Ascophyllum Nodosum interacts with 22 drugs
Interaction Rating Key
These severity listings are for informational use only. Never start, stop or otherwise change your therapy before speaking with your provider.
| Major | The combined use of these agents is strongly discouraged as serious side effects or other negative outcomes could occur. |
| Moderate | Use cautiously under the care of a healthcare professional or avoid this combination. A significant interaction or negative outcome could occur. |
| Minor | Be aware that there is a chance of an interaction. Watch for warning signs of a potential interaction. |
| Unknown | No interactions have been reported or no interaction data is currently available. |
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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
Drug descriptions are provided by MedlinePlus.
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In addition to being a clinical pharmacist specializing in pharmacotherapy, Dr. Brian Staiger is a registered herbalist through the American Herbalist Guild. He has combined his passion for pharmacy practice with the study of medical ethnobotany to improve patient care. Feel free to reach out about any of your herbal or medication questions!
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