Drugs used in thyrotoxicosis (anti-thyroid drugs)
Definition
Drugs used to reduce thyroid hyperactivity
Two forms
1. Irradiation by radioisotope I 123 or I 131 - destroy thyroid tissue
2. Antithyroid medications - interfere with the synthesis of thyroid hormones and other agents that control manifestations of hyperthyroidism
Radioactive Iodine Therapy
Aim : destruction of overactive thyroid cells
Most commonly used in the elderly patients
The isotopes enter the body and are concetrated in the thyroid gland; destroy thyroid cells without jeopardizing (endangering) other radiosensitive tissues.
In several weeks the thyroid cells are destroyed - reduction of hyperthyroid state and inevitably hypothyroidism
Tasteless, coloreless drug
Administered by a radiologist
A single dose of the drug is administered
80 to 160 µCi/g of estimated thyroid gland weight
About 70 % to 85 % of patients are cured by one dose
About 10% to 20% require two doses, rarely a third dose
Initially Hyperthyroidism may occur - look for thyroid storm - propranolol to be used to control
Patient is followed closely for at least 10 to 20 years for hypothyroidism - Thyroid hormone replacemet in gradually increasing doses
Contraindicated in pregnancy and lactation
Hypermetabolic state has to be controlled by antithyroid medications before radioactive iodine is administered to guard from thyroid storm on administration of the isotopes
Antithyroid Medications
Inhibit one or more stages in thyroid hormone synthesis or hormone release
May reduce the amount of thyroid tissue with resulting decreased thyroid hormone production
Propylthiouracil (Propacil, PTU)
Methimazole (Neomercazole)
Given until the patient is euthyroid.
After that maintenance dose is established
Then gradually withdrawn over the next several months
Periodic hematologic studies done; look for agranulocytosis
Adjunctive Therapy
Iodine or iodide compounds
They decrease the release of thyroid hormones from the thyroid gland and reduce the vascularity and size of the thyroid.
Potassium iodide (KI), Lugol’s solution, and saturated solution of potassium iodide (SSKI)
May be used in combination with antithyroid agents or beta-adrenergic blockers to prepare the patient with hyper-thyroidism for surgery.
They make the surgical procedure safer.
More palatable in milk or fruit juice and are administered through a straw to prevent staining of the teeth.
Nursing Alert
Patients observed for the development of goiter and should be cautioned against use of Cough medications, expectorants, bronchodilators, and salt substitutes which may contain iodide
Beta-adrenergic blocking agents
Control the sympathetic nervous system effects of hyperthyroidism.
Propranolol (Inderal) is used to control nervousness, tachycardia, tremor, anxiety, and heat intolerance.
Used with extreme caution in elderly patients to minimize adverse effects on cardiac function that may produce heart failure.
Recurrent Hyperthyroidism
The relapse rate after depends on the dose used in treatment.
Hypothyroidism
Occurs in almost 80% of patients at 1 year and in 90% to 100% by 5 years.
