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adrenergic pharmacology
board prep
27
Medical
Graduate
03/03/2008

Additional Medical Flashcards

 


 

Cards

Term

 

 

Adrenergic junction (catecholamine synthesis)

Definition
Tyrosine --> Dopa (via tyrosine hydroxylase) --> Dopamine --> NE (via dopamine beta hydroxylase) --> NE placed in storage vesicle --> released into junction to act on alpha and beta receptors  
Term

 

 

 

What can happen to NE once released

Definition

Can bind to its receptor alpha or beta

 

Can be metabolized by COMT enzyme

 

Can be taken back up into neuron (MC b/c short 1/2 life)

 

Can have neg. feedback on alpha2 auto recetpor

Term

 

 

 

Where can drugs effect the adrenergic junction (hint 8 places) 

Definition

Methyl-p-tyrosine inhibits tyrosine to Dopa step

MAOI's inhibits the free metabolism of NE keeping them around longer for use

Amphetamines central release of NE, and DA via binding to the MAO transporters

Cocaine/TCA's Na/K reuptake blocked leaving it in the junction longer

Alpha 2 agonist/antagonists

Reserpine destroys the storage vesicles for NE

Guanethidine inhibits exocytosis

Alpha and Beta agonists/antagonists

 

Term

 

 

 

Alpha 1 receptor

Definition

Eye -- contraction of radial muscle, mydriasis

 

Arterioles/veins -- vasoconstricts, increases TPR/diastolic pressure/afterload from the aa

and increases venous return/preload from the vv

 

Bladder -- contraction, urinary retention

 

Liver -- increases glycogenolysis

kidney -- decreases renin release

 

 

Term

 

 

 

Alpha 2 receptor

Definition

Negative feedback

 

Prejunctional nerve terminals (decrease NE release)

 

Platelets -- aggregation

 

Pancreas -- decrease insulin secretion

Term

 

 

 

Beta 1 receptor

Definition

Heart

SA node -- increase HR (positive chronotropy)

AV node -- increase conduction velocity

Atrial and ventricular muscle -- increase force of contraction (positive ionotropy), CV, CO, O2 consumption

His-Pukinje -- increase automaticity and CV

Kidney -- increase renin release

Term

 

 

 

Beta 2 receptors

Definition

Mostly not innervated (Epi)

 

Blood vessels -- vasodilation, decreases TPR/diastolic pressure,afterload

Uterus -- inhibit contractions/relaxation

Bronchioles -- dilation

Skeletal muscle & liver -- increase glycogenolysis

Pancreas -- increase insulin secretion

Term

 

 

 

Beta vs alpha receptors  

Definition
Beta receptors are usu more sensitive to activators than alpha receptors so drugs that exert both effects like (Epi) the beta responses are dominant at low doses and alpha at high doses
Term

 

 

 

Alpha 1 agonists 

 

 

 

Definition

Phenylephrine = nasal decongestant, ophthalmologic

Methoxamine = paroxysmal atrial tachycardia (b/c cause reflex bradycardia but low on list of choices)

 

Alpha 1 = increase TPR, BP, potential for reflex bradycardia (decreased HR)

 

Increase in mean BP via vasoconstriction 

Term

 

 

 

Alpha 2 agonists 

Definition

Clonidine & Methyldopa = mild to moderate HTN

 

Stimulate prejunctional receptors in the CNS to decrease sympathetic outflow 

Term

 

 

 

Beta agonists 

Definition

Isoproterenol = (B1=B2) used for bronchospasm, heart block, and bradyarrhythmias

 

SE's: flushing, angina, arrhythmias

 

Dobutamine = (B1>B2) used for CHF

 

salmeterol, albuterol, terbutaline = B2 selective for asthma 

Ritodrine = B2 selective used in premature labor

 

B1's = increase HR, SV, CO, and pulse pressure

B2's = decrease TPR, BP  

Term

 

 

 

Mixed-Acting Agonists (NE) 

Definition

Alpha 1,2 and Beta 1

 

Alpha 1 = increase TPR, BP

Beta 1 = increase HR, SV, CO, pulse pressure

Potential reflex bradycardia

 

Net effect on HR is initially increased followed by a decrease long term  

Term

 

 

 

Mixed Agonists (Epi) 

Definition

Alpha 1,2 and Beta 1,2

 

Low dose Epi = all beta effects so increase HR, SV, CO, and pulse pressure and decrease TPR and BP

 

Medium dose Epi = both betas and some alpha 1 get the increased HR, SV, CO and pulse pressure but then the Beta2 and alpha1 cancel eachother out (mean BP stays the same)

 

High dose Epi = get mostly alpha effects, looks very similar to NE (increased TPR,BP w/ potential for reflex bradycardia and initial tachycardia from beta 1 at the beginning)

Term

 

 

 

Differentiate b/n NE and high dose Epi  

Definition

Give an alpha 1 blocker (eg: phenoxybenzamine) and if the pt had been given high dose Epi will actually see hypotension b/c the Beta 2 receptors have been unmasked (versus the alpha 1 causing initial HTN d/t the vasoconstriction of the blood vessels)

 

Remember NE doesn't stimulate Beta 2 receptors at all so won't see the hypotension  

Term

 

 

 

Uses of NE and Epi (5)

Definition

 

Cardiac arrest

Adjunct to local anesthetic

Hypotension

Anaphylaxis (epi only)

Asthma (epi only) 

Term

 

 

 

Indirect acting adrenergic receptor agonists (Releasers) 

Definition

Displace NE form the mobile pool (more available)

 

Major DI: MAO(a) inhibitors (can lead to a hyptertensive crisis)

 

Tyramine (red wine, cheese)

Amphetamines (eg methyl phenidate) used in ADHD & narcolepsy causes central release of DA, NE, 5HT

Ephedrine (cold medication)

 

These can ONLY work on effector tissues innervated by the sympathetic system b/c they do nothing to the alpha or beta receptors 

 

 

 

 

Term

 

 

 

Indirect acting adrenergic receptor agonists

(reuptake inhibitors)  

Definition

Leave the NE around longer in the synapse

 

Cocaine and TCA's

Term

 

 

 

Alpha receptor antagonists

(effects and uses) 

Definition

Decrease TPR and mean BP

 

May cause reflex tachycardia and salt/H2O retention

 

Uses: HTN, pheochromocytoma (nonselective), BPH (alpha 1 selective)

 

 

Term

 

 

 

Nonselective alpha blockers  

Definition

Phentolamine = competitive inhibitor

 

Phenoxybenamine = noncompetitive inhibitor (irreversibly binds) 

Term

 

 

 

Selective alpha 1 blocker  

Definition
Prazosin, doxazosin, terazosin, tamsulosin (last one specifically blocks the 1a receptor found in the prostate
Term

 

 

 

Selective alpha 2 blockers 

Definition

Yohimbine = postural hypotension and impotence (b/c w/o the negative feedback from the alpha 2 receptors the alpha 1 can continue)

 

Mitazapine = used as an antidepressant 

Term

 

 

 

Beta blockade (general effects) 

Definition

Beta 1 blockade = decrease HR, SV, CO, renin release, aqueous humor production

 

Beta 2 blockade = precipitate bronchospams, and vasospasm in pts w/ these disorders

Also blocks glycogenolysis and gluconeogenesis (problem in diabetics)

Can increase LDL's and TG's 

Term

 

 

 

Beta blocker drugs (+general uses) 

Definition

Acebutolol, Atenolol, Metoprolol (1st half of the alphabet is beta 1 selective) so safer in asthmatics, diabetics, and peripheral vascular dz

 

Pindolol, Propranolol, Timolol (2nd half is nonselective)

 

Acebutolol and Pindolol both have intrisic sympathomimetic activity and act as partial agonists causing slight vasodilation and minimal change in lipids 

 

Used for angina, HTN, post-MI

Antiarrhythmics (propranolol, acebutolol, esmolol)

Glaucoma (timolol)

Migraine, thyrotoxicosis, performance anxiety, essential tremor (propranolol b/c overstimulation of beta 2 on skeletal mm) 

 

Term

 

 

 

Combined alpha 1 and beta blocking 

Definition

Labetalol & Carvedilol

 

used for CHF  

Term

 

 

 

K+ channel blockade and Beta blocking 

Definition

Sotalol

 

Used as an antiarrhythmic  

Term

 

 

 

Open angle glaucoma (+treatment) 

Definition

Chronic condition w/ increased intraocular pressure  d/t decreased reabsorption of aqueous humor

 

Leads to progressive painless visual loss

 

Strategy in treatment = beta blockers (timolol) to decrease formation of fluid and muscarinic activators (pilocarpine) to improve drainage through the canal of Schlemm  

Term

 

 

 

Closed angle glaucoma (+ treatment) 

Definition

Acute, painful condition w/ increased IOP d/t the blockade of the canal of Schlemm

 

Emergency treatment involving a cholinomimetic, carbonic anhydrase inhibitor, and/or mannitol

 

Pilocarpine, Acetazolamide, Mannitol 

1st = muscarinic agonist causes contraction of ciliary muscle which increases flow through canal

2nd = decreases aqueous humor formation

3rd = osmotic diuretic 

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