AUTONOMIC DRUGS Adrenergic and Antiadrenergic Drugs Presented by

AUTONOMIC DRUGS (Adrenergic and Antiadrenergic Drugs) Presented by Sasan Zaeri (Pharm. D, Ph. D)

Adrenergic Agonists

Direct acting adrenergic drugs

Location Receptor type Effect Heart Β 1, β 2 ↑ heart rate ↑ force of contraction Skin and splanchnic vessels α 1 constriction Skeletal muscle vessels β 2 dilation β 2 relaxation α and β relaxation Radial pupillary dilator α 1 contraction (mydriasis) Ciliary epithelium β ↑ secretion of aqueous humor Vascular Smooth Muscle: Other smooth muscle: Bronchiole Uterine GI tract Eye:

Beta I Receptor Activation Beta 1 receptors are located in the heart Therapeutic uses Cardiac arrest Heart failure Shock Atrioventricular (AV) block

Beta II Receptor Activation Beta 2 receptors are located in the lung and uterine Therapeutic uses Asthma Delaying of preterm labor

Alpha I Receptor Activation Alpha 1 response: Constriction of blood vessels & mydriasis Therapeutic uses Vasoconstriction Mydriasis Nasal or ophthalmic decongestion

Alpha II Receptor Activation Alpha 2 receptors are located presynaptically Activation inhibits NE release Activation of alpha 2 receptors in CNS is very important: causes reduction of sympathetic response in heart and blood vessels

Indications for use of adrenergic drugs: Cardiac arrest: Hypotension and shock: Bronchodilators (β 2) Ophthalmic or nasal congestion: Increase blood pressure (α 1) Asthma: Cardiac stimulant (β 1) Decongestant (α 1) (oral or topical decongestant) Prevention of preterm labor: Tocolytic (β 2)

Properties of Representative Adrenergic Agonists Epinephrine Therapeutic uses To cause vasoconstriction Treatment of sever asthma Treatment of anaphylactic shock

Salbutamol: Selective β 2 agonist Dilates bronchial smooth muscle Clinical use: Antiasthmatic

Antiadrenergic Drugs

ADRENERGIC BLOCKING DRUGS Also called sympatholytic drugs Classified according to their site of action α – adrenergic antagonists β – adrenergic antagonists α 2 – adrenergic agonists

α antagonists Phenoxybenzamine: Irreversible antagonist Used to treat pheochromocytoma (catecholamine-secreting tumour of the chromaffin tissue) Prazocin: Relaxes the smooth muscle in the blood vessels; increases dilation of blood vessels; and decreases blood pressure Caution: orthostatic hypotention

ß-Adrenergic Blockers Are selective or nonselective Nonselective beta-blockers affect beta 1 receptor sites located mainly in the heart and beta 2 receptor sites located in the bronchi, blood vessels, and uterine Propanolol

ß-Adrenergic Blockers Selective beta-blockers primarily affect beta 1 receptor Atenolol and metoprolol

ß-Adrenergic Blockers Effects on the heart include: decreased heart rate decreased force of heart contractions decreased blood pressure

ß-Adrenergic Blockers Clinical uses: Ischemic heart disease: Ø↓ HR and force of contraction ØLessens work of heart Hypertension Arrhythmias

ß-Adrenergic Blockers Also used to treat Tremor Stage fright Cardiovascular symptoms associated with thyrotoxicosis Migraine headaches Glaucoma

ß-Adrenergic Blockers Caution for diabetics β – antagonists will suppress glycogenolysis and delay recovery during hypoglycemic episodes Any β – antagonist will mask tachycardia – a warning sign of hypoglycemic events β 1 – selective antagonist is better choice

ß-Adrenergic Blockers Adverse effects: Bradycardia and heart block Bronchospasm Drug interactions: Other antihypertensive agents Insulin and oral hypoglycemic agents