Autonomic Antagonists Flashcards
What is atropine?
Competitive antagonist for muscarinic receptor’s ACh binding site (ie parasympathetic antagonist)
What does atropine do to the HR?
inc
What does atropine do to the AVN refractory pd
dec
What does atropine do to arteriolar vasodilation
dec
What do we use atropine clinically for?
- Interrupt or prevent a vagal rxn
- Restore AV conduction in disorders that cause prolonged AV nodal refractoriness
- ->inferior wall MI
- ->Digitalis intoxication
What would a beta 1 antagonist do?
- Dec HR
- Dec velocity, inc refractoriness
- Dec myocardial intotropy and metabolic rate
- Inhibit renin release
What is prazosin?
Competitive alpha 1 antagonist (with a little alpha 2)
-inhibits vasoconstriction decreasing PVR and BP
Side effect of prazosin?
postural hypotension
What are doxazosin and terazosin
pure alpha 1 antag that have a slower onset and longer duration than prazosin
Why does a greater lipid solubility of a drug matter?
Greater lipid sol=more readily penetrates BBB
Which beta blockers are lipophilic?
propranolol, metoprolol (abs in GI, metab by liver, short T1/2)
What beta blockers are hydrophilic?
Atenolol (longer T1/2, renal metab)
What is propranolol?
Non selective beta blocker with high lipid solubility, short half life and hepatic elimination and low bioavailability
What is metoprolol?
Beta 1 antagonist with moderate lipid solubility, high bioavailability and hepatic elimination
What is atenolol
Beta 1 blocker with low lipid sol, 40% bioavailability and renal elimination
What is carvedilol?
Non selective beta blocker with additional alpha 1 blockade, moderate lipid sol, hepatic elimination
What CV conditions do we use beta blockers for?
HF, MI, Angina, Arrhythmias, hyperT
–>don’t give with complete heart block or cardiogenic shock
Adverse effects of beta blockers
- Sinus bradycardia, sinus arrest AV block
- Reduced LV contractility in severe symptomatic HF
- Bronchoconstriction
- Fatigue, mental depression, nightmares, sexual dysfxn
- Raynaud’s precipitation
- Worsening of limb ischemia with severe PVD
- Withdrawal (tachy arrhythmias, angina etc because beta1 receptors become upregulated with chronic use)
- Inc TGs, dec HDL
- Can mask symptoms of hypoglycemia in diabetes
Do we use beta blockers for cardiogenic shock?
NO WAY! He has to do whatever he can to maintain output, including very increased HR.
Who are the ideal pts for beta blocker use?
- Physical activity induces attacks of angina
- Coexistent hyperT
- Hx of supraventricular or ventricular arrhythmias
- Previous MI
- Left ventricular systolic dysfxn
- Mild to moderate HF symptoms
- Prominent anxiety state
Poor candidates for beta blockers
- asthma/lung disease
- SEVERE LV dysfxn with HF
- Hx of depression
- Raynauds
- Symptomatic peripheral vascular disease
- Brittle diabetes
- Severe bradycardia or heart block
