Anti–Adrenergics (aka Adrenergic Antagonists)

• Remember, these drugs have parasympathetic effects (dumbels)

• Blocks alpha receptors effecting: smooth muscle (vasodilation causing orthostatic hypertension) and increase in HR (reflex sympathetic stimulation); presynaptic terminals (abolish/reverse catecholamine effects); pancreatic beta cells (decreased insulin release); trigone and sphincter of bladder (urination)

• Larger doses hits more receptors

1. Phenoxybenzamine – pheochromocytoma; used for irreversible alpha blockade

2. Phentolamine – used for frost bite

• Similar to above: slight increase in HR (reflex sympathetic stimulation); increased contractility due to inhibition of phosphodiesterase (degrades cAMP); "first dose phenomenon" causing syncope (fainting) and subduing reflex response.

1. Prazosin, doxosin – chronic hypertension and hypertensive emergencies; Raynaud's disease; frost bite; benign prostatic hypertrophy, heart failure (decreased preload/afterload)

1. Yohimibine – used for male sexual dysfuntion

• Competitively reduce Beta receptor occupancy causing parasympathetic effects

• Indicated for: hypertension, cardiac arrhythmia, angina pectoris, glaucoma, migraines, anxiety/panic attacks

• Contraindications: (see chart above); pt's with diabetes (masking of symptoms of caused by hypoglycemia); asthma and COPD; elderly (induced hypothermia)

• Intrinsic sympathomimetic activity (ISA) and partial agonists – "PAL" (propranolol, acebutolol, labetalol)

• Membrane stabilizing activity (MSA); local anesthetic – "LAMPP" (labetalol, acebutolol, metoprolol, pindolol, propranolol)

1. Propranolol – used as a local anesthetic, enters CNS; similar to carvedilol but without 1 effects

2. Nadolol, timolol, pindolol, careolol, sotalol – used as a local anaesthetic; nadolol  CNS

1. Acebutolol, atenalol, betaxolol, esmolol, metoprolol – esmolol IV only; metoprolol enters CNS; atenalol  CNS

• Predominantly alpha and beta1 blockers causing decrease TPR (orthostatic hypotension), no change in HR and CO (partial agonist activity), reflex tachycardia

1. Labetalol, carvedilol – partial agonist (l)

1. Metyrosine –used for pheochromocytoma (too much catecholamines) with alpha blockers to inhibit tyrosine hydroxylase in catecholamine synthesis

2. Guanethidine – inhibits release of norepinephrine and depletion of norepinephrine stores

3. Reserpine – blocks storage of norepinephrine

• Receptor Agonists – Nicotine, carbachol, cholinesterase inhibitors

• Receptor Antagonists – Trimethaphan, mecmylamine, tubocurarine (blocks at Nn receptor), anti–muscarinics

• Low/intermediate dose – stimulates cardiovascular system, anorexia, nausea, urination

• Large dose – depolarization blockade, depression, apnea, paralytic ileus.

Category: Pharmacology Notes