Sympathomimetics Flashcards
What is a monoamine?
-one amino group connected to aromatic ring by two-carbon chain
-serotonin, dopamine, Norepinephrine, epinephrine, Histamine
What is a catecholamine?
monoamine + catechol group [benzene w/2 hydroxyl groups]
-dopamine, Norepinephrine, epinephrine
Describe the metabolism of catecholamines.
COMT: liver, nerve terminals; metabolism of circulating and administered catecholamines
MAO: liver, nerve terminals, kidney, gut; surface membrane protein of mitochondria
What effects are observed at a1 (Gq) receptor?
Vasoconstriction (innervated), Pupillary dilation, Ejaculation, Inhibition of micturition, GI inhibition
What effects are observed at a2 (Gi) receptor?
Vasoconstriction (uninnervated), Prejunctional inhibition of NE release, In CNS: decrease cardiovascular SNS input
What effects are observed at B1 (Gs) receptor?
Cardiac stimulation (innervated), Secretion of renin
What effects are observed at B2 (Gs) receptor?
Cardiac stimulation (uninnervated, minor), Bronchodilation, Uterine relaxation, GI inhibition, Vasodilation (uninnervated)
What receptor is not metabolized by both MAO and COMT?
B2
What agonists are Norepinephrine selective for?
-a1 and B1
-metabolized by MAO and COMT
What agonists are Epinephrine selective for?
a1 (high doses), B1, and B2
-extra methyl group makes for B2 selectivity
-metabolized by MAO and COMT
What agonists are Dopamine selective for?
low doses- D1 & B1
high doses- a1
What is a1 clinically manipulated for?
Agonists-
Nasal decongestion
Vascular failure in shock and tachycardia
Antagonists-
Hypertension
Benign prostatic hyperplasia
Pheochromocytoma
What is Phenylephrine?
-direct a1 agonist
-metabolized by MAO
-nasal decongestant
What are imidazolines?
-partial agonists at a-receptors
-much more hydrophobic/lipophillic
What is a2 clinically manipulated for?
Agonist
-Hypertension
-Pain
-Glacoma
What is Clonidine?
-direct a2 agonist
-Hypertension, Neuropathic pain, ADHD
-imidazoline structure noted
What is the relationship with Methyldopa and Methyldopate?
Methyldopa (Aldomet) is a prodrug given orally due to low water solubility
Methyldopate is a prodrug with good water solubility given parenteral
-hypertension
What a2 agonist can help with treatment of glaucoma?
Brimonidine
-inhibits production and increase outflow of aqueous humor; decreases intraocular pressure
What is B1 clinically manipulated for?
Agonist
-shock
-Congestive heart failure
Antagonist
-Hypertension
-Angina
-Arrhythmia’s
-Congestive heart failure
What is B2 clinically manipulated for?
Agonist
-asthma
-premature labor
Antagonist
-Glaucoma (not common)
What is B3 clinically manipulated for?
Agonist
-overactive bladder
What is isoproterenol?
-B1 & B2 selective
-used to increase heart rate, patients with systolic dysfunction, asthma and COPD
What is the baroreceptor reflex?
-detects changes in blood pressure
low blood pressure: induces tachycardia and vasoconstriction to increase BP
high blood pressure: induces bradycardia to decrease BP
What are the B2 selective agonists that are Resorcinol derivatives?
-Metaproterenol (Alupent, Metaprel)
-Terbutaline (Bricanyl, Brethine)
-used for Asthma, COPD, premature labor
