Adrenergic antagonists

Selective alpha 1 blockers MOA

block NE actions on alpha 1 receptors in vascular smooth muscle → inhibit vasoconstriction → lower BP

first generation alpha 1 antagonist

prazosin (short acting)

non selective prostatic a1a and vascular a1b

second generation alpha 1 antagonists

terazosin, doxazosin, alfuzosin (long acting)

non selective prostatic a1a and vascular a1b

third generation alpha 1 antagonists

tamsulosin, silodosin

selective a1a prostatic receptors

adverse effects of 1+2 generation alpha 1 antagonists

first dose effect → postural orthostatic hypotension, syncope, tachycardia, dizziness, nasal congestion

adverse effects of 3rd generation alpha 1 antagonists

less CV S/E, ejaculatory dysfunction, floppy iris syndrome

beta blockers MOA

competitive antagonists at beta receptors

• pindolol and acebutolol are partial agonists (ISA)

Non selective beta blockers examples

propranolol, timolol, nadalol

pindolol (ISA)

selective (b1) beta blockers

atenolol, metoprolol, esmolol

acebutolol (ISA)

beta 1 receptor blockade effects (in all b blockers)

antihypertensive

• decrease HR and contractility

• decrease renin release

  • both of these will lower BP (in hypertensive pts, not in normotensive pts)

beta 2 receptor blockade effects (only in non selective b blockers)

• bronchoconstriction

• decrease glucose production

  • potentiate hypoglycemia in diabetics

• decreased lipolysis, increased TG and decreased HDL over time

all beta blockers mask symptoms of what disease state?

hypoglycemia symptoms

• tachycardia, palpitations, tremors

does not mask sweating though

less masking with ISA b blockers

Labetalol

non selective b blocker + selective alpha 1 blocker

for hypertensive emergency

Timolol is (hydrophilic/lipophilic)

lipophilic, good for eye administration (for glaucoma)

What is significant about esmolol?

short half life (3-4 minutes)

Adverse effects of beta 1 blockage

hypotension, bradycardia (exercise intolerance), AV block, cause acute HF in pts with impaired cardiac function, mask hypoglycemia

adverse effects of b2 blockage

bronchoconstriction, hypoglycemia, dyslipidemia

Contraindications for all beta blockers

sinus bradycardia, HF, partial AV block

contraindications for non selective beta blockers

asthma, COPD

use with caution in diabetes

Why should dose be tapered when going off of beta blockers?

Sudden stop causes rebound HTN, angina, and arrhythmias due to upregulation of beta receptors during drug therapy. This can be really dangerous.