Antiadrenergics Flashcards
What does an adrenergic antagonist do?
Competes with norepinephrine (NE) or epinephrine (Epi) for receptor binding
What is the effect of an adrenergic receptor antagonist?
Causes effects opposite to sympathetic nervous system activation
How can receptor inactivation affect the target organ?
It can either inactivate or activate the organ, depending on the receptor type
What is prazosin?
A selective α1 receptor antagonist that does not block α2 receptors at clinical doses.
How does prazosin work?
It blocks α1 receptors, preventing NE from causing arterial smooth muscle contraction, leading to relaxation and lower blood pressure.
What is the main therapeutic use of prazosin?
Treatment of high blood pressure.
What is a common side effect of prazosin?
Nasal congestion.
What is propranolol (Inderal) and nadolol (congard)?
A nonselective β receptor antagonist (beta blocker).
How does propranolol and nadolol work?
It prevents β receptors from transducing the signal, antagonizing the effects of NE.
What are the therapeutic indications for propranolol and nadolol?
Treatment of high blood pressure, chest pain (angina), and prophylactic treatment of migraines.
When does propranolol and nadolol have the most effect?
It primarily affects responses during excitement, stress, or physical exertion, rather than at rest.
Why are non-selective β1 and β2 antagonists contraindicated in patients with asthma?
They can antagonize β2 receptors, leading to smooth muscle spasms and a reduction in airway diameter, potentially triggering an asthma attack.
What role does epinephrine play in maintaining airway diameter?
Epinephrine, released by the sympathetic nervous system, helps maintain the diameter of the trachea, bronchi, and terminal bronchioles.
What is a safer alternative for asthma patients regarding β antagonists?
A selective β antagonist, which avoids blocking β2 receptors, can prevent these side effects.
What type of drug is metoprolol?
A selective β1 receptor antagonist.
How does metoprolol work?
It antagonizes the action of norepinephrine (NE).
When does metoprolol have the most effect?
It mostly affects responses during excitement, stress, or physical exertion.
What are the therapeutic indications for metoprolol?
Treatment of high blood pressure and chest pain.
What type of drug is guanethidine?
An indirectly acting adrenergic antagonist.
How does guanethidine work?
It inhibits NE release by being taken up by NET and replacing NE in synaptic vesicles, depleting the available NE for release.
What was guanethidine primarily used for?
It was used as a treatment for hypertension.
Why is guanethidine rarely used now?
It causes many sympathetic side effects, including hypotension and diarrhea.
