Trachte Week 3 Flashcards
Name three sympathomimetics that induce release of norepinephrine, but NOT dopamine B hydroxylase?
tyramine, amphetamine, ephedrine
How do indirectly acting sympathomimetics act to induce release of norepi?
they reverse the direction of the axoplasmic catecholamine transporter
What drugs make the action of tyramine, amphetamine and ephedrine inactive? how?
imipramine, cocaine via inhibition of the axoplasmic pump
What med inhibits the granular pump accumulating catecholamines in vesicles (results in depletion of catecholamines)?
Reserpine (Serpasil)
Name the med that induces release from vesicle, probably via displacement, slow acting (nor epi gets degraded by MAO), depletes norepi stores, reduces responses to sympathetic stimulation, inactive in the presence of inhibitors of the axoplasmic transporter or MAOIs
Guanethidine
What is present in the liver and is needed for inactivating circulating catecholes?
COMT
What blocks the COMT and is used as adjunct tx in Parkinsons?
Tolcapone (Tasmar)
What is the function of MAO? What blocks it’s action?
oxidizes catecholamines, perlindole in the intestine and brain, seligeline and PARGYLINE in various organs
What is the purpose of MAOIs?
potentiate the action of catecholamines
What do you have to avoid when taking an MAOI? why?
Foods containing tyramine, because they also release catecholamines and are normally degraded by MAO in the intestine
What is the predominant end product of norepi?
vanilylmandelic acid in urine
Name the receptor: adrenergic cardiac effects, renin release, located in heart, JG apparatus and adipose, acts to increase cAMPT via Galphas
Beta1 (isoproterenol>epinephrine=norepinephrine)
Name the receptor: mediates smooth muscle contraction (primary CV location is blood vessels), activates phospholipase C (Galphaq dependent process) to increase intracellular calcium via inositol triphosphates
Alpha1 (epinephrine > norepi»_space;isoproterenol
Name the receptor: inhibition of neural norepinephrine release, prejunctional nerve terminal, platelets, gut, medulla oblongata, acts to decrease cAMP or activate cAMP or activate Na/H antiporter, Galpha dependent process
Alpha2 (epi>norepi»isoproterenol)
Name the receptor: relaxation of smooth muscle and metabolic (glycogenolytic) effects, primary site in CV system is blood vessels (smooth muscle in general), acts to increase cAMP via Galphas
Beta2 (isoproterenol > epi»_space; norepi)
What is the action of Dobutamine?
selective B1 agonist, positive ionotrope
Define Ionotrope
increases cardiac contractility (ie Ca to increase Ca from SR)
Define Chronotrope
increase heart rate (activates funny current in SA node)
Define Dromotrope
increase rate of action potential (alters conductivity of gap junctions, particularly in the AV node)
What is a contraindication of dobutamine?
atrial fibrillation
When do you use dobutamine? how?
CHF or acute MI with heart failure; IV
How does dobutamine effect BP? What blocks this affect?
increases heart rate, stroke volume and BP
What is the action of Phenylephrine?
alpha1 agonist (non-catecholamine agents)
What is Phenylephrine used to tx?
reverse hypotension, and paroxysmal atrial tachycardia, also used as a decongestant (5mg oral) topical vasoconstrictor and mydriatic
What is used to tx orthostatic hypotension?
Midodrine (ProAmatine); an alpha1 agonist
What is the action of Albuterol?
B2 selective agonist (structurally not catecholamines)
What is Albuterol used to tx?
bronchodilation (asthma), delay labor
What are the major AE of Albuterol (B2 agonists)?
tachycardia (B1), palpitations (B1), tremor (B2) and headache (B2 vasodilation)
What effect does Albuterol (B2 agonist) have on BP?
relaxes vasculature so decreased BP
What are the actions of epinephrine on A1, B2, HR?
usually vasoconstricts A1, can vasodilate B2 and directly increases HR and force but reflexes to the elevation in BP can suppress HR (vagal stimulation)
How is epi metabolized?
MAO and COMT
What are contraindications for epi?
hyperthyroidism, HTN, halogen-hydrocarbon anesthetics
Name 4 therapeutic uses for epi?
- hypersensitivity rxns (low BP and broncho spasm) A1 and B2 2. w/anesthetics for vasoconstriction A1 3. topical hemostatic A1 4. restore heart beat B1
What effect does epi have on BP?
can raise or lower it….conflicting effects
What is the action of epi on BP after Terazosin (an alpha blocker)?
decrease BP b/c only have action of vasodilating B2
What is the action of Norepinephrine?
vasoconstriction (A1), increased HR and force (B1), reflex reduction in HR mediated via vagus
Contraindications to norepinephrine?
hyperthyroidism (more beta receptors on the heart), anesthesia, pregnancy
Therapeutic use of norepi?
hypotension
How does norepi effect BP?
raises it
Name a synthetic catecholamine that stimulates B receptors
Isoproterenol
Action of isoproterenol?
vasodilate (B2), tachycardia (B1)
How is isoproterenol metabolized?
COMT and MAO
What is the therapeutic use of Isoproterenol?
cardiac stimulant (B1)
How do indirectly acting agents (amphetamine a phenylethylamine; ephedrine; pseudoephedrine) release norepi from nerves?
reversing the catecholamine axoplasmic uptake pump to release norepi from the nerves (increase BP)
