Methimazole (Antithyroid)
Wondering whether you can take something with Methimazole (Antithyroid)? Use this interaction reference to help frame questions about combining it with other products.
1 supplements in this library have a recorded interaction with this medication
Dangerous combinations
Supplements recorded as risky with this medication1 listedHighest severity first
- →SupplementsSea Moss (Irish Moss)TheoreticalCaution
Excess iodine from sea moss can override the antithyroid effect of Methimazole, potentially causing loss of thyroid control and thyrotoxicosis.
Where the evidence comes from
- Reference knowledge
Open Sea Moss (Irish Moss)Confidence
confidence 70/100
- Trade names
- Methimazole (Tapazole)
Full write-up
What is it
Methimazole (Antithyroid) is a metabolic drug in the antithyroid family, also known by the brand name Methimazole (Tapazole). It is generally used in situations involving thyroid activity.
This page provides educational reference about combining it with other products, including supplements. A clinician can help assess potential interactions in the context of a specific medical condition or treatment plan.
What interacts with it
The most important concerns are supplements that can alter thyroid hormone production or make thyroid tests misleading. Ashwagandha may increase T3 or T4, potentially opposing methimazole’s antithyroid effect. Sea Moss (Irish Moss) can provide excess iodine, which may counteract methimazole by supplying substrate for thyroid hormone production and could lead to loss of thyroid control. Iodine supplements can also interfere with the medication’s mechanism and alter the treatment response in hyperthyroidism. These concerns overlap because both Sea Moss (Irish Moss) and Iodine may increase iodine exposure.
Vitamin B7 (Biotin) may create a laboratory pattern resembling hyperthyroidism. This could lead to unnecessary initiation or escalation of methimazole and, in turn, iatrogenic hypothyroidism; the concern is therefore about interpreting thyroid tests as well as the medicine itself. Holy Basil (Tulsi) leaf extract reduced circulating T4 in animals, so an additive antithyroid effect and excessive thyroid suppression are possible, although this finding does not establish the same effect in people.
Iodine has a specialized, supervised use in some situations: in thyroid storm or selected preoperative Graves disease, pharmacologic iodide may be given after methimazole to acutely inhibit thyroid hormone release while methimazole blocks new hormone synthesis. This combination requires strict medical supervision and should not be treated as routine supplementation. Selenium may be used adjunctively with methimazole in selected patients with Graves disease and mild active orbitopathy; the therapies address complementary aspects of the disease rather than producing a pharmacokinetic interaction. Anyone using these combinations, or having thyroid laboratory results interpreted while taking supplements, can discuss them with a prescriber or pharmacist.