Adrenergics:β adrenergic receptor antagonists Flashcards
Minor actions of B adrenergic recpetor antagonists
partial agonists (i.e., activate β receptors partially in the absence of catecholamines; however, the intrinsic activities of these drugs are much less thana full agonist);
- local anesthetic or quinidine-like activity
- block α1 receptors
- vasodilating properties
Non-Subtype-Selective β Adrenergic Receptor Antagonists known as
(“First Generation”)
Prototype B adrenergic receptor antagonists
Propranolol
Propranolol works by:
Competitive reversible blockade of both β1 and β2 receptors
Propranolol works on B1, B2, both receptors
both
Propranolol is used for:
Hypertension -
Angina -
Certain cardiac arrhythmias due to excess catecholamines or that respond to a
reduction in heart rate/AV conduction velocity
- Acute myocardial infarction
- Pheochromocytoma (adrenal tumor =excess NE
- Migraine prophylaxis
Side effects of propranolol on HR Airway sugars others
Side Effects
- Cardiac depression, bradycardia/heart block
- May increase airway resistance
- Mask symptoms of hypoglycemia
- Sedation, impotence, nightmares
A patient has asthma and congestive heart failure. is propranonolol safe?
Use with caution in patients with:
If a patient has bradyarrhythmias, AV block or hypotension, are we safe to prescribe propranolol?
prescribe propranolol with caution, may exacerbate those
What drug should we be wary of when prescribing heart meds to individual with insulin-dependent diabetes?
Propranolol
insulin-dependent diabetes prone to hypoglycemic episodes
supersensitivity to β adrenergic stimulation which may cause angina, arrhythmias, or infarction could be caused by
Withdrawal syndrome from propranolol
Timolol (Timoptic®) is:
non-selective β receptor antagonist
Therapeutic use of timolol
angina/hypertension/pherochromocytoma/ arrythmias d/t excess catecholamines/ acute myocardial infarction
same as propranolol
widely used in the treatment of wide angle glaucoma
Timolol
How does timolol help with wide angle glaucoma
- decreases aqueous humor formation by ciliary epithelium leading to decreased intraocular pressure
What affect does timolol have on pupil size and accomidation?
- does not affect pupil size or accommodation and is devoid of blurred vision and night blindness seen with miotics
What is the benefit to a pt with wide angle glaucoma to systemic installation of Timolol?
- small amounts can be absorbed systemically after installation in eye; use with caution in patients with cardiac disease
β1 – Selective Adrenergic Receptor Antagonists
(“Second Generation”)
Prototype 2nd generation drug
– Metoprolol (Lopressor®)
(“Second Generation”)
β1 – Selective Adrenergic Receptor Antagonists
Major pharmacological actions of Metoprolol
- Competitive, reversible β1 receptor blocker
- at low doses is more selective at blocking the β1 receptor (~10-fold selective)
What dose is metoprolol best as selectively blocking the B1 receptor
low dose… 10 fold more selecive
Metoprolol is a
reversible/non-reversible
competitive/non-competitive
B1/B2 receptor blocker
competitive
reversible
B1
Metoprolol has same therapeutic effects as:
propranolol
treat heart failure
only three β blockers
tested in clinical studies and proven to slow rate of heart failure progression and to increase survival time
(metoprolol,carvedilol, bisoprolol)
For Metoprolol the side effects are similar to propranolol except….
- less bronchoconstriction at lower doses
Atenolol is orally active: dosing is:
once a day
Does atenolol penetrate the CNS
does not penetrate into the CNS – less CNS side effects -
What do we use atenolol for?
therapeutic use: similar to propranolol (except for migraine prophylaxis)
Atenolol is:
B1 antagonist
β receptor antagonists with additional cardiovascular effects
(“Third Generation”)
“Third Generation” drugs include
Labetalol
Carvedilol
competitive antagonist of α1 receptor and both β receptors (non-selective)
- therapeutic use: essential hypertension (oral) and hypertensive emergencies
(IV)
Labetalol
therapeutic use: essential hypertension (oral) and hypertensive emergencies
(IV)
Labetalol
competitive antagonist of α1 receptor and both β receptors (non-selective) -
also has anti-oxidant properties and anti-inflammatory effects
- blocks L-type calcium channels at higher doses
Carvedilol (Coreg®) -
therapeutic use: chronic heart failure, hypertension, and acute MI
Carvedilol
Carvedilol is a competitive antagonist of :
α1 receptor and both β receptors (non-selective)
at higher doses, carvedilol will:
blocks L-type calcium channels