Adrenergic Drugs Flashcards by Stephanie Wordes

What is the biosynthesis and release of Catecholamines pathway? (8)

(1) Phenylalanine to Tyrosine (enzyme: phenylalanine hydroxylase)
(2) Tyrosine uptake into nerve cell
(3) Tyrosine to DOPA (enzyme: tyrosine hydroxylase)
(4) Dopa to Dopamine (enzyme: aromatic acid decarboxylase)
(5) Uptake of Dopamine into storage granules by active transport mechanism (also transports NE)
(6) Dopamine to NE (enzyme: dopamine beta-hydroxylase)
(7) NE to Epinephrine in adrenal medulla (enzyme: phenylethanolamine N- methyl transferase)
(8) Release of NE into synaptic cleft during nerve stimulation. Storage vesicles, containing the NE, fuse with neuronal membrane

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What is the rate limiting step of the biosynthesis of Catecholamines?

Tyrosine Hydroxylase

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What are 3 Catecholamines? Which one is the most prevalent?

(1) Norepinephrine**
(2) Epinephrine
(3) Dopamine

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What are the 3 ways in which catecholamines are removed from biophase?

(1) Neuronal reuptake (uptake 1). Active transport of catecholamine into neuron where metabolized or taken back up into storage granule
(2) Diffusion into circulation
(3) Active transport (uptake 2) into post-junctional cells

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What is the most important process in the removal of catecholamines?

Uptake 1 (pre-synaptic uptake mechanism)

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What are the 2 ways the catecholamines are metabolized?

(1) Monoamine Oxidase (MAO): located in both neurons and post-junctional cells. Deaminates catecholamines
(2) Catechol-O-methyltransferase (COMT): located in post-junctional cells. Catalyzes the O-methylation of catecholamines

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What are the two systems that impact the Sympathetic Nervous System? What do they do?

Sympathomimetics: mimics SNS activation and enhances SNS activity
Sympatholytics: block sympathetic neurotransmission

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What are the 3 types of Sympathomimetics?

(1) Direct activity: act directly on the receptor (Epi, NE, Isoproterenol)
(2) Indirect activity: effect catecholamine levels in synapse (e.g. catecholamine release or uptake- Amphetamine, Tyramine, Cocaine, Imipramine)
(3) Combination: have mixed actions (Dopamine, Ephedrine)

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What does indirect activity of sympathomimetics mean?

The actions of an indirect agent are dependent upon the presence of endogenous catecholamines (bind to post-synaptic adrenergic receptors)

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What are the 3 Catecholamine Receptors?

(1) Alpha-adrenergic receptors
(2) Beta-adrenergic receptors
(3) Dopamine receptors

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What are the subtypes of Alpha receptors? What are they known for doing?

(1) Alpha-1: smooth muscle contraction (vasoconstriction)

2) Alpha-2: pre-synaptic regulation of NT release (negative feedback mechanism

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What are the non-selective Alpha agonists and antagonists?

Agonists: Epi>NE>Isoproterenol (Epi and NE are better than Isoproterenol which is a beta agonist)
Antagonists: Phentolamine and Phenoxybenzamine

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What are the subtypes of Beta receptors? What are they known for doing?

(1) Beta-1: cardiac stimulation (heart rate, contractility)

2) Beta-2: smooth muscle: bronchodilation (lung) and vasodilation (e.g. vessels in skeletal muscle

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What are the selective Alpha receptor subtypes?

Alpha-1: selective agonist- Phenylephrine
selective antagonist: Prazosin
Alpha-2: selective agonist: Clonidine
selective antagonist: Yohimbine

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What is the non-selective Beta antagonist?

Propranolol

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What are the Agonists and Antagonists of Beta receptors?

Beta-1: Agonists potency rank Iso>Epi=NE
- selective antagonist: Metoprolol
Beta-2: Agonist potency rank: Iso>Epi>NE
- selective agonists: metaproterenol,
albuterol, ritodrine

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What are dopamine receptors?

CNS and renal localization (Agonist selectivity: Dopamine»Epi)

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What is the selective antagonist of B-1 receptors?

Metoprolol

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What are the selective agonists for B-2 receptors?

Metaproterenol, Albuterol, Ritodrine

What type of receptor does Norepinephrine work on?

A-1=A-2=B1»B2

What are the cardiovascular actions of Norepinephrine? What is the change in cardiac output?

Increase TPR
Increase BP (increase in S and D)
Reflex decrease in HR
No change in CO (increase in SV due to increase in venous return and B-1 effects in ventricle)

What is the formula for BP?

BP= HR x SV x TPR

- HR x SV= CO-

What type of receptor does Phenylephrine work on?

A-1 agonist

What are the cardiovascular actions of Phenylephrine?

Similar to NE (increase TPR, BP, decrease HR)

What type of receptors do Epinephrine work on?

B-1=B2>A-1=A-2

What are the cardiovascular actions of low dose of Epinephrine? High dose?

- Decrease in TPR - Slight increase to no change in mean BP - Increase HR - Decrease renal and cutaneous flow - At high dose, like NE -

What type of receptors does Isoproterenol work on?

B-1 and B2 agonists

What are the cardiovascular actions of Isoproterenol?

Similar to lose dose Epi with subtle difference | - Slight decrease in mean BP due to greater decreases in TPR and DBP (but not enough to stimulate reflex)

What type of receptors does Ephedrine work on?

Mainly indirect action but some direct (A and B agonists)

What are the cardiovascular actions of Ephedrine?

- Increase contractility - Increase HR at low/mod doses - High dose: Increase SBP, DBP, MBP with reflex bradycardia

What other action does Ephedrine do?

Bronchodilation via B-2 in lungs | - Long duration of action

What type of receptors does Albuterol work on?

B2 selective agonist

What does Albuterol do?

- Relaxation of airway smooth muscle | - are stimulated in vasculature with systemic administration

What type of receptors does Dopamine work on?

Dopamine, B1 and alpha agonists

What are the cardiovascular actions of Dopamine?

- increase renal blood flow - Moderate dose: increase contractility and HR, increase CO, tachycardia less than isoproterenol - High dose: increase TPR

What type of receptors does Dobutamine work on?

B1 and some A agonist

What are the cardiovascular actions of Dobutamine?

- Increase in contractility, HR, and CO (tachycardia less than iso) - High dose: Increase in TPR

What type of receptors do Phenoxybenzazmine and Phentolamine work on? Which is irreversible?

non-selective alpha antagonists; Phenoxybenzamine irreversible

What are the cardiovascular actions of Phenoxybenzamine and Phentolamine?

- Decrease in TPR - Increase in BP in upright individual - No change or slight decrease in supine - Reflex increase in HR

What are the adverse effects of Phenoxybenzamine and Phentolamine?

postural hypotension and tachycardia

What type of receptors does Prazosin work on?

alpha 1 selective antagonist

What cardiovascular actions act upon Prazosin?

Similar to non-selective drugs | - Less reflex increase in HR

What type of receptors does Propranolol work on?

non-selective beta antagonists

What are the cardiovascular actions on Propranolol?

B-1: - Decrease HR, AV nodal conduction, contractility, CO - Decrease renin release; decrease BP in hypertensive patient B-2: - acute increase peripheral vascular resistance - increase airway resistance

What are the adverse effects of Propranolol? Precautions?

(1) Cardiac depression (2) Lassitude (3) depression - asthma and diabetes precautions

What type of receptors does Metoprolol work on?

Beta 1 selective antagonists

What are the cardiovascular actions of Metoprolol?

B-1: - Decrease HR, AV nodal conduction, contractility, CO - Decrease renin release; decrease BP in hypertensive patient - Little or no effect on airway resistance and peripheral vascular resistance