Dr. Ogbru received his Doctorate in Pharmacy from the University of the Pacific School of Pharmacy in 1995. He completed a Pharmacy Practice Residency at the University of Arizona/University Medical Center in 1996. He was a Professor of Pharmacy Practice and a Regional Clerkship Coordinator for the University of the Pacific School of Pharmacy from 1996-99.
Jay W. Marks, MD, is a board-certified internist and gastroenterologist. He graduated from Yale University School of Medicine and trained in internal medicine and gastroenterology at UCLA/Cedars-Sinai Medical Center in Los Angeles.
DRUG CLASS AND MECHANISM: Methimazole is used to treat an overactive
thyroid gland (hyperthyroidism).
Grave's disease is the most common cause of hyperthyroidism. It is an autoimmune disease
resulting from antibodies that attach to receptors on thyroid hormone-producing cells in the thyroid gland and trigger overproduction of thyroid hormone. An enzyme (peroxidase)
produces thyroid hormones, i.e., thyroxine (T4) and triiodothyronine (T3), by combining iodine with a protein called thyroglobulin.
Methimazole prevents iodine and peroxidase from their normal interactions with
thyroglobulin to form T4 and T3. This action decreases thyroid hormone
production. Methimazole also interferes with the conversion of T4 to T3. Since
T3 is more potent than T4, this also reduces the activity of thyroid hormones.
The FDA approved methimazole in March 1999.
GENERIC AVAILABLE: Yes
PRESCRIPTION: Yes
PREPARATIONS: Tablet: 5, 10, and 15 mg
STORAGE: Methimazole should be stored at room temperature, 15-30 C
(59-86 F).
PRESCRIBED FOR: Methimazole is used for treating hyperthyroidism. It
also is used for decreasing symptoms of hyperthyroidism in preparation for
surgical removal of the thyroid gland or before inactivating the thyroid gland
with radioactive iodine. Long-term use of methimazole may lead to a remission of
the hyperthyroidism.
DOSING: The initial adult dose of methimazole is:
15 mg/day for mild
hyperthyroidism,
30-40 mg/day for moderately severe hyperthyroidism, and
60
mg/day for severe hyperthyroidism.
The daily dose is divided into three doses
administered every 8 hours. The maintenance dose is 5-15 mg/day. The usual
initial children's dose is 0.4 mg/kg given in 3 divided doses administered 8
hours apart, and the maintenance dose is half the initial dose.
DRUG INTERACTIONS:Warfarin (Coumadin) works by reducing the activity
of vitamin K and therefore the formation of vitamin K dependent clotting
factors. Methimazole may increase the activity of warfarin by further reducing
the activity of vitamin K in the body.
PREGNANCY: There is evidence that methimazole may cause harm to the
fetus during pregnancy.
NURSING MOTHERS: Methimazole is excreted in
breast milk and may
potentially cause harm to the infant.
SIDE EFFECTS: Methimazole is generally well-tolerated with side
effects occurring in 3 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.
Hyperthyroidism is an excess of thyroid hormone resulting from an overactive thyroid gland. Symptoms can include increased heart rate, weight
loss, depression, and cognitive slowing. Treatment is by medication, the use of
radioactive iodine, thyroid surgery, or reducing the dose of thyroid hormone.
There are many types of thyroid disease. Some occur due to the function of the thyroid itself such as hypothyroidism, hyperthyroidism, Hashimoto's thyroiditis, etc. Some causes of thyroid disease occur due to problems with the structure of the thyroid gland such as goiters, thyroid nodules, and thyroid cancer. Treatment of thyroid disease depends on the cause of the disease.
Graves' disease is an autoimmune disease that affects the thyroid. Some of the symptoms of Graves' disease include hand tremors, rapid heartbeat, trouble sleeping, enlarged thyroid, thinning of the skin or fine brittle hair. Causes of Graves' disease are thought to be multifactorial such as genes, gender, stress, and infection. Treatment for Graves' disease is generally medication.
Thyroiditis is the inflammation of the thyroid gland. The inflamed thyroid gland can release an excess of thyroid hormones into the blood stream, resulting in a temporary hyperthyroid state. Some forms of thyroiditis can be diagnosed based on tenderness and enlargement of the thyroid gland. A thyroid scan sometimes is used in making the diagnosis. Thyroiditis can also be diagnosed with a biopsy of the thyroid gland.
Thyroiditis (thy-roi-DY-tiss) is inflammation, or swelling, of the thyroid.
There are several types of thyroiditis, one of which is Hashimoto's thyroiditis.
What are other types and symptoms of thyroiditis?
Postpartum thyroiditis
Like Hashimoto's thyroiditis, postpartum thyroiditis seems to be caused by a
problem with the immune system. In the United States, postpartum thyroiditis
occurs in about 5 to 10 percent of women. The first phase starts 1 to 4 months
after giving birth. In this phase, you may get symptoms of hyperthyroidism
because the damaged thyroid is leaking thyroid hormones out into the
bloodstream. The second phase starts about 4 to 8 months after delivery. In this
phase, you may get symptoms of hypothyroidism because, by this time, the thyroid
has lost most of its hormones. Not everyone with postpartum thyroiditis goes
through both phases. In most women who ha...
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