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Methimazole

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3.1 Effectiveness

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RateADrug users have reported 9 Methimazole side effects and 4 Methimazole benefits.

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Description | Uses & Side Effects | Warnings

There is currently no information to display in this section. RateADrug provides information about drugs and supplements though a wiki format provided by researchers, health care providers and others. We encourage you to add to this description by clicking on the button below.

Common Uses:

Methimazole is indicated in the medical treatment of hyperthyroidism. Long-term therapy may lead to remission of the disease. Methimazole may be used to ameliorate hyperthyroidism in preparation for subtotal thyroidectomy or radioactive iodine therapy. Methimazole is also used when thyroidectomy is contraindicated or not advisable.

Off Label Uses:

Currently there are no known off label uses for Methimazole.

Side Effects:
Methimazole is generally well-tolerated with side effects occurring in three out of every 100 patients.

The most common side effects are related to the skin and include rash, itching, hives, abnormal hair loss, and skin pigmentation. Other common side effects are swelling, nausea, vomiting, heartburn, loss of taste, joint or muscle aches, numbness and headache.

Less common but more serious side effects include a decrease in white blood cells (agranulocytosis) and blood platelets (thrombocytopenia). Symptoms and signs of agranulocytosis include infections of the throat, the gastrointestinal tract, and skin with an overall feeling of illness and fever. Since platelets are important for the clotting of blood, thrombocytopenia may lead to problems with excessive bleeding. Hepatitis and death of liver cells (hepatic necrosis) have rarely been associated with methimazole.

Cautions / Warnings:

Methimazole may cause drowsiness, dizziness, or lightheadedness. These effects may be worse if you take it with alcohol or certain medicines. Use Methimazole with caution. Do not drive or perform other possibly unsafe tasks until you know how you react to it.

Lab tests, including thyroid and liver function tests, complete blood cell counts, and blood clotting tests (eg, PT, INR), may be performed while you use Methimazole. These tests may be used to monitor your condition or check for side effects. Be sure to keep all doctor and lab appointments.

Methimazole has been shown to cause harm to the fetus. If you think you may be pregnant, contact your doctor. You will need to discuss the benefits and risks of using Methimazole while you are pregnant. Methimazole is found in breast milk. Do not breast-feed while taking Methimazole .

Agranulocytosis is potentially a serious side effect. Patients should be instructed to report to their physicians any symptoms of agranulocytosis, such as fever or sore throat. Leukopenia, thrombocytopenia, and aplastic anemia (pancytopenia) may also occur. The drug should be discontinued in the presence of agranulocytosis, aplastic anemia (pancytopenia), hepatitis, or exfoliative dermatitis. The patient's bone marrow function should be monitored.

Drug Interactions:
Drug interactions with Methimazole include the following:

Anticoagulants (oral) - The activity of oral anticoagulants may be potentiated by anti-vitamin-K activity attributed to Methimazole.

ß-adrenergic blocking agents - Hyperthyroidism may cause an increased clearance of beta blockers with a high extraction ratio. A dose reduction of beta-adrenergic blockers may be needed when a hyperthyroid patient becomes euthyroid.

Digitalis glycosides - Serum digitalis levels may be increased when hyperthyroid patients on a stable digitalis glycoside regimen become euthyroid; a reduced dosage of digitalis glycosides may be required.

Theophylline - Theophylline clearance may decrease when hyperthyroid patients on a stable theophylline regimen become euthyroid; a reduced dose of theophylline may be needed.

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Methimazole Comments

27 Feb 2013

I began the Methimazole in September of 2012. The first week was bad. Ups and downs and really bad headaches but then the headaches stopped and my energy level returned and things seemed to level out. My second lab that was drawn showed normal levels - then into the fourth month I began having that racing feeling with my heart and was so tired and had the shakes again and could barely stay awake and when I did sleep I never felt rested. My immediate thought was , this medication needs to be decrease and lo and behold I was right. The last labs drawn on Feb 14, 2013 showed the levels to be low ...so my DOC decreased the Methimazole to 10 mg per day half in the morning, half at night and within two days I began getting ready bad headaches. I was told this would happen until is all levels out again and my energy returns. I just do not know what to think, I hate medication and have not been sick in 22 years. When my blood pressure was out of control this past September it was my first ER visit in years and they are yelling HEART and I am saying NO THYROID ... do I know my own body or what? Endo wanted to yank ti out or do RA Iodine and I said " When pigs fly" My DOC is so great and he said "Look I know you are Holistic and do not like drugs but please try the Methimazole and if it does not agree with you I will take you off it " I trust my DOC so I took it for the four plus months. It's only been two days since the decrease and the headache from hell is what i have. Can anyone please explain that to me?

—Posted by Anonymous

13 Nov 2012

I am on my second week of taking these meds. Its worked great so far and hoping it continues to improve. I've been dealing with the symptoms (muscle/weight loss, shakes, memory loss - at night body is basically paralyzed from neck down) for about 3-4 months. I don't know what the normal symptoms are, and I've read that some have dealt with it for awhile. If it is anything like what I had, I do hope you find relief soon. The quality of life this has given back to me thus far is incredible. I haven't noticed any side effects so far, however it has only been 2 weeks. I read some deal with insomnia, I've had insomnia issues as far back as I can remember so not sure it changes anything for me. Bottom line for me is that it lets me hold my wife and play with my kids again.

—Posted by Cas A

07 Sep 2012

My major problem with Methimazole, which I have taken for the past 6 months, is severe insomnia which makes me so very exhausted during the day. I have never been a very good sleeper, but this is ridiculous! I have also lost half of my hair. I am having blood work next week and a follow-up with my endocrinologist a week later and hope to get some answers. To be fair, this drug has made my thyroid numbers fall in to the normal range.

—Posted by Tired Lady

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About Methimazole

Methimazole (1-methylimidazole-2-thiol) is a white, crystalline substance that is freely soluble in water. It differs chemically from the drugs of the thiouracil series primarily because it has a 5-instead of a 6-membered ring. Each tablet contains 5 or 10 mg (43.8 or 87.6 µmol) Methimazole, an orally administered antithyroid drug. Each tablet also contains inactive ingredients: lactose monohydrate, magnesium stearate, starch pregelatinized and talc. Methimazole inhibits the synthesis of thyroid hormones and thus is effective in the treatment of hyperthyroidism. The drug does not inactivate existing thyroxine and triiodothyronine that are stored in the thyroid or circulating in the blood nor does it interfere with the effectiveness of thyroid hormones given by mouth or by injection. The actions and use of Methimazole are similar to those of propylthiouracil. On a weight basis, the drug is at least 10 times as potent as propylthiouracil, but Methimazole may be less consistent in action. Methimazole is readily absorbed from the gastrointestinal tract. It is metabolized rapidly and requires frequent administration. Methimazole is excreted in the urine.

About Methimazole

Methimazole (also known as Thiamazole) is an antithyroid drug similar in action to propylthiouracil, and part of the thioamide group.

Source: Wikipedia

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