CH 38 Table - Thyroid & Antithyroid Drugs

MOA of thyroid preparations?

activation of nuclear receptors results in gene expression with RNA formulation & protein synthesis

What thyroid preparations exist?

1. levothyroxine (T4)

2. Liothyronine (T3)

Clinical application of thyroid preparations?

hypothyroidism

Pharmacokinetics of Thyroid preparations?

max effect seen after 6-8 weeks of therapy

Symptoms of thyroid excess?

1. warm, moist skin

2. sweating, heat intolerance

3. tachycardia (increased SV, CO, pulse pressure)

4. dyspnea

5. increased appetite

6. nervousness, hyperkinesia, tremor

7. weakness, increased deep tendon reflexes

8. menstrual irregularity, decreased fertility

9. weight loss

10. retraction of upper lid with wide stare, exophthalmos (Grave's disease)

Symptoms of hypothyroidism?

1. pale, cool, puffy, yellowish skin, face & hands; brittle hair & nails

2. sensation of being cold

3. bradycardia (decreased SV, CO, pulse pressure)

4. pleural effusions, hypoventilation & CO2 retention

5. reduced appetite

6. lethargy, general slowing of mental processes

7. stiffness, decreased deep tendon reflexes

8. infertility, decreased libido, impotence, oligospermia

9. weight gain

10. drooping of eyelids

Thioamides therapy options?

1. propylthiouracil (PTU)

2. methimazole

MOA of thioamides?

1. inhibit thyroid peroxidase reactions

2. inhibit iodine organification

3. inhibit peripheral conversion of T4 to T3

Clinical application of thioamides?

hyperthyroidism

Pharmacokinetics of thioamides?

1. oral administration

2. delayed onset of activity

Toxicites/drug Ix of thioamides?

1. nausea

2. GI disturbances

3. rash

4. agranulocytosis

5. hepatitis (PTU-warning)

6. hypothyroidism

Iodide therapy options?

1. Lugol's solution, potassium iodide

2. radioactive iodine (RAI)

MOA of Iodides?

1. inhibit iodine organification & hormone release

2. reduce size & vascularity of thyroid gland

3. radiation-induced destruction of thyroid parenchyma

Clinical applications of Iodides?

1. preparation for surgical thyroidectomy

2. hyperthyroidism (patients should be euthyroid or on Beta blockers before RAI)

3. avoid in pregnancy & in nursing mothers

Pharmacokinetics of Iodides?

1. oral administration

2. acute onset on activity within 2-7 days

Toxicities/Drug Ix of Iodides?

1. sore throat (rare)

2. hypothyroidism (rare)

Beta blocker therapy?

1. propranol

2. other beta blockers lacking partial agonist activity

MOA of Beta blockers?

1. inhibition of Beta receptors

2. inhibition of conversion of T4 to T3 (Propranolol only)

Clinical applications of Beta Blockers?

1. thyroid storm

2. adjunct to control tachycardia, HTN, atrial fibrillation

Pharmacokinetics of Beta blockers?

rapid onset of activity

Toxicities/Drug Ix of Beta blockers?

1. asthma

2. AV blockade

3. hypotension

4. bradycardia