Levothyroxine (T4) (Synthroid)

Thyroid replacement agent

Drug of choice for pts needing thyroid hormone replacement

Should be taken on an empty stomach in the morning, at least 30 min before breakfast

Converted to T3 in the body

1/2 life: 7 days

S/E: Rare in appropriate doses

OD: Thyrotoxicosis: Tachycardia, angina, tremor, insomnia, sweating may occur

Should dec doses of warfarin and catecholamines

Propylthiouracil (PTU)

Thyroid hormone inhibitor

Inhibits conversion of T4 to T3 in the periphery

Full benefits may take 6-12 months to develop (Does not destroy existing stores of thyroid hormone)

Most serious S/E: Agranulocytosis

Preferred drug during pregnancy b/c it crosses the placenta poorly

Radioactive Iodine (131 I)

Drug for Hyperthyroidism

Used in Graves' Disease

Destroys thyroid tissue

Objective: produce clinical remission w/out causing complete destruction of the gland

Full effects develop in 2-3 months

~66% of pts w/ Graves' disease are cured w/in a single exposure to 131 I

Big consequence: Delayed hypothyroidism is common

For pts who haven't responded to other drugs/treatments

Not for use in pregnancy and young children

Inderal (Propranolol)

Beta Blocker

Used for Graves' Disease

Can suppress tachycardia and other symptoms of Graves' disease

Benefits derive from beta-adrenergic blockade

Work quickly

Beneficial in throtoxic crisis; should receive one immediately in this case

Growth Hormones

Hypothalamus release GH- releasing hormone (GH-RH), which stimulates release of GH from the pituitary

This causes liver and other tissues to release insulin-like growth factor-1 (IGF-1)

Peds GH excess: gigantism

Adult GH excess: acromegaly

GH can elevate glucose levels in pts with DM

Promotes: growth, protein synthesis

Vasopressin (Pitressin)

ADH replacement

ADH deficiency results in hypothalamic diabetes insipidus

Warn pt to dec H2O intake; failure to do so can cause H2O intoxication

Identical to natural ADH

Can cause profound vasoconstriction

By promoting vasonconstriction, can be lifesaving in pts with cardiac arrest (receiving CPR, inc blood flow to heart and brain)

Hydrocortisone

Glucocorticoid

Used for adrenocortical insufficiency

Identical structure to cortisol

Oral doses for chronic replacement therapy

S/E: None in low doses.

Adrenal suppression and Cushing's syndrome can develop w/ chronic, large doses used for nonendocrine treatments

Fludrocortisone (Florinef)

Mineralcorticoid

Only mineralcorticoid available; drug of choice for mineralcorticoid replacement

Used for Addison's disease, primary hypoaldosteronism, and congenital adrenal hyperplasia

Usually combined w/ a glucocorticoid

S/E: When doses are too high: salt and water retained, K+ lost

F&E imbalance should resolve spontaneously in a few days

Ketoconazole (Nizoral)

Corticosteroid suppression

Antifungal that also inhibits glucocorticoid synthesis

Used in pts w/ Cushing's syndrome

Used only as an adjunct to surgery or radiation

Doses are higher than in antifungal therapy

Glucocorticoids

Anti-inflammatory/immunosuppressant effects

Suppress: 1. Synthesis of inflammatory mediators (prostaglandins, leukotrienes, histamine)

2. Infiltration of phagocytes

3. Release of lysosomal enzymes

4. Proliferation of lymphocytes

Glucocorticoids

Adverse Effects

Adrenal Insufficiency

Osteoporosis (Suppression of bone formation by osteoblasts)

Infection (Risk of acquiring one is inc)

Glucose Intolerance (Can inc plasma glucose levels)

Myopathy (Muscle weakness; arms and legs affected most)

F&E Imbalance (Na & H2O retention, K+ loss)

Growth Retardation (Children)

Cataracts & Glaucoma

PUD (Inhibit prostaglandin synthesis)

Glucocorticoids

Route and Dose Recommendations

Routes: Oral, parenteral (IV, IM, SQ), topical, intranasal, local injection (intra-articular, intralesional), inhalation

Local therapy (topical, nasal, inhalation, local injection) minimizes systemic toxicity, so is preferred over oral or parenteral

When systemic effects are needed, oral is preferred over parenteral

Dose: Low initially, then gradually increased until symptoms are under control

Inc dose will be needed during times of stress