Thyroid Drugs

3 actions of the thyroid hormones:

1. stimulate energy use
2. stimulate the heart
3. promote growth and development

the 4 thyroid hormone replacements:

- levothyroxine (Synthroid)
- Liothyronine (cytomel,triostat)
- liotrix (euthyroid)
- thyroid desiccated (armor thyroid)

4 antithyroid agents:

- methimazole (tapazole)
- propylthiouracil (PTU)
- radioactive Iodine
- nonradioactive iodine (lug's solution)

deficient thyroid hormone, lifelong treatment, almost always in adults and sometimes infants

hypothyroidism

symptoms of hypothyroidism:

weight gain, hair loss, intolerance to cold, no appetite, facial and eyelid edema, extreme fatigue, brittle hair and nails, muscle aches and weakness

thyroid agent that treats hypothyroidism, identical to naturally occurring thyroid hormone, given PO, IV form is available, highly protein bound, once per day dosing

Levothyroxine (Synthroid, levoxyl)

When should levothyroxine be administered?

30-60 mins before breakfast

When does levothyroxine reach half life?

1 week

when does levothyroxine reach plateau?

1 month

adverse reactions of levothyroxine:

- thyrotoxicosis
- osteoporosis
- Atrial fibrillation

symptoms of hyperthyroidism

thyrotoxicosis

levothyroxine absorption is decreased by:

- calcium, mg
- antacids
- H2 blockers
- sucralfate
- cholesterol binding agents

what foods should be avoided when taking levothyroxine:

- soy formula
- cotton seed meal
- high fiber foods

3 drugs that accelerate metabolism of levothyroxine:

- phenytoin
- carbamazepine
- rifampin

levothyroxine increases effects of this anticoag, levothyroxine accelerated the degradation of vitamin K dependent clotting factors

Warfarin

thyroid hormones increase the responsiveness of this drug, use it cautiously, includes epinephrine, dopamine, and dobutamine

Catecholamines

levothyroxine can increase the requirements for both of these drugs

Insulin and digoxin

is levothyroxine safe in pregnancy?

yes, dosage might need to be increased

excessive thyroid hormone secretion, can cause grave's disease, weight loss, jitters, enlarged thyroid, facial flushing

Hyperthyroidism

drug to treat hyperthyroid, first line drug that is recommended unless pregnant, inhibits thyroid hormone synthesis, doesn't do anything to what is already released but will prevent it

Methimazole (tapazole)

What can methimazole cause?

may induce hypothyroidism and can cause agranylocytosis

reduction of granulocytes that's needed to fight infection, most serious and dangerous toxicity

Agranylocytosis

treats hyperthyroidism, second line drug ,inhibits thyroid hormone synthesis and prevents conversion of T4 to T3 in the periphery, can take when pregnant

Propylthiouracil (PTU)

When is propylthiouracil (PTU) preferred?

during thyroid storm/thyrotoxic crisis

used for thyroid cancer or hyperthyroidism, should not use if pregnant/lactating or for children

Radioactive Iodine

a high dose of radioactive Iodine is used for...

thyroid cancer

a low dose dose of radioactive iodine is used for...

hyperthyroidism

used for hyperthyroidism, is a paradoxical inhibition of thyroid hormone secretion, used for short, used in nuclear radiation emergencies, and is an antiseptic

nonradioactive iodine

what may nonradioactive iodine be used before

thyroidectomy

can treat hyperthyroidism, suppresses symptoms by blocking beta receptors

Beta blockers

what type of patent are beta blockers contradicted in?

asthma patients