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43 terms

Indirect-Acting Adrenergic Agonists (15)

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List 2 types of indirect-acting adrenergic agonists.
releasing agents

uptake inhibitors
List 3 releasing agents (indirect-acting adrenergic agonist).
amphetamine

methylphenydate

tyramine
Tyramine mechanism
causes norepinephrine release from presynaptic terminals

- potentiates effects of NE produced endogenously
List 2 ways by which amphetamines increase blood pressure.
increases blood pressure by alpha-agonist action on vasculature

increases blood pressure by beta-stimulatory effects on heart

- has central stimulatory action
Name a structural analogue of amphetamine widely used to treat ADHD in children.
methylphenidate
Releasing agent (indirect-acting adrenergic agonist) found in fermented food such as ripe cheese and Chianti wine
tyramine
Tyramine drug interaction
tyramine is normally oxidized by MAO

patients taking MAO inhibitors can manifest serious vasopressor episodes
Ephedrine actions on blood pressure and respiratory system
increases systolic and diastolic blood pressures

bronchodilation
Ephedrine mechanism and uses (2)
stimulates alpha and beta receptors and releases NE from nerve endings
- poor substrate for COMT and MAO since it is not a catecholamine
- excellent absorption orally and penetrates the CNS

sometimes used prophylactically in chronic treatment of asthma to prevent attacks

mild stimulation of CNS: increases alertness, decreases fatigue and prevents sleep
Pseudoephedrine uses
available over the counter as a component of many decongestant mixtures
Phenoxybenzamine mechanism and uses (2)
irreversible non-selective alpha antagonist

prior to surgical removal of pheochromocytoma

chronic management of inoperable tumors

- non-selective alpha antagonists usually not successful for hypertension
How does blockade of alpha1-adrenergic receptors affect sympathetic tone of blood vessels and peripheral vascular resistance?
reduces sympathetic tone of blood vessels and decreases PVR
Phentolamine mechanism and uses (4)
reversible non-selective alpha antagonist
-----
short term control of hypertension

diagnosis of pheochromocytoma by phentolamine blocking test

hypertensive crisis associated with stimulant drug overdose (cocaine)

hypertensive crisis due to sudden withdrawal of sympatholytic anti-hypertensive drugs, e.g. clonidine
The systemic blood pressure decreases in response to epinephrine given with pretreatment of phenoxybenzamine. What is this phenomenon called?
epinephrine reversal

- the vasoconstrictive alpha1 action of epinephrine is blocked, but the vasodilation caused by activation of beta2-receptors is not
Alpha1-selective adrenergic blockers use
treatment of hypertension
Alpha1-blockers CV effects
lower arterial blood pressure by relaxing both arterial and venous smooth muscle
Why must the first dose of alpha1-blockers be 1/3 or 1/4 of the normal dose?
the first dose produces an exaggerated hypotensive response that can result in syncope
Are alpha1-blockers the drugs of choice for hypertension?
no
Drug class of choice for benign prostatic hyperplasia symptom relief
alpha1-blockers

- relaxes smooth muscle in the bladder neck, prostate capsule and prostatic urethra, improving urinary flow
Terazosin mechanism and use (2)
alpha1-blocker with longer half-life than prazosin

- used for hypertension and BPH
Doxazosin mechanism and use (2)
alpha1-blocker with longer half-life

- used for hypertension and BPH
Tamsulosin mechanism and use
alpha1-blocker

- used for BPH

- little effect on bp, so less likely to cause orthostatic hypotension
Yohimbine mechanism and use
alpha2-selective adrenergic blocker

- used in the past to treat erectile dysfunction <-- phosphodiesterase type 5 inhibitors have replaced it
Propranolol mechanism
non-selective beta-blocker
How do beta-blockers affect heart rate and myocardial contractility?
slow heart rate

decrease myocardial contractility
Why are non-selective beta-blockers contraindicated in patients with asthma?
blocking beta2 receptors in the lungs can precipitate a respiratory crisis in patients with COPD or asthma
How do non-selective beta-blockers affect glycogenolysis and glucagon secretion?
decreases both
Non-selective beta-blockers uses (3/9)
hypertension
- beta-blockers lower blood pressure in hypertension by decreasing CO

glaucoma
- diminish intraocular pressure

migraine
- effective prophylaxis
- mechanism may depend on blockade of catecholamine-induced vasodilation of brain vasculature

hyperthyroidism
- beta-blockers blunt sympathetic stimulation

angina pectoris
- decrease O2 requirement of heart muscle
- not for acute management

atrial fibrillation
- control ventricular rate

MI
- protective effect on the myocardium

performance anxiety
- preferred Rx

essential tremor
- most commonly used drugs for treatment
List 2 reasons that diabetics should be careful while taking non-selective beta-blockers.
non-selective beta-blockers may impair recovery from hypoglycemia in insulin-dependent diabetics

mask the tachycardia that is typically seen with hypoglycemia, denying the patient an important warning sign
List 2 ways in which non-selective beta-blockers adversely affect one's serum lipid profile.
inhibit TAG breakdown in adipose tissue

reduce HDL, increase LDL, increase TAGs

- beta1-blockers improve serum lipid profile of dyslipidemic patients
Why is it important to not withdraw beta-blocker therapy abruptly?
up-regulation of beta-receptors due to long-term therapy can cause acute tachycardia, hypertension, and/or ischemia upon abrupt withdrawal
Nadolol mechanism and uses (2)
non-selective beta-blocker

- management of angina pectoris
- management of hypertension
Timolol mechanism and uses (3)
non-selective beta-blocker

- treatment of hypertension
- prophylaxis of migraine headache
- treatment of intraocular hypertension or open-angle glaucoma
What 2 patient populations (with specific disorders) benefit from beta1-selective adrenergic antagonists?
hypertensive patients with impaired pulmonary function

diabetic hypertensive patients who are receiving insulin or oral hypoglycemic agents
Atenolol mechanism and uses (3)
beta1-selective adrenergic antagonist

- management of hypertension
- long-term management of angina pectoris
- management of MI to reduce CV mortality
Metoprolol mechanism and uses (3)
beta1-selective adrenergic antagonist

- management of hypertension
- long-term management of angina pectoris
- management of MI to reduce CV mortality
Esmolol mechanism and uses
ultra-short acting beta1-selective adrenergic antagonist (half-life = ~10 minutes)

- supraventricular arrhythmias
- arrhythmias associated with thyrotoxicosis
- perioperative hypertension
- myocardial ischemia in acutely ill patients
Labetalol mechanism and use
competitive antagonist at beta and alpha1 receptors

- management of hypertension

* substantially more potent as a beta-antagonist than as an alpha-antagonist
Carvedilol mechanism and uses (2)
competitive antagonist at beta- and alpha1-receptors

- used in hypertension and congestive heart failure

* substantially more potent as a beta-antagonist than as an alpha-antagonist
Pindolol mechanism and uses
partial beta-agonist

- antihypertensive in individuals with diminished cardiac reserve or a propensity to bradycardia

* not demonstrated in controlled trials, but may be important in individual patients
Alpha-methyltyrosine (metyrosine) mechanism and uses (2)
competitive inhibitor of tyrosine hydroxylase (inhibits NE synthesis)

- management of malignant pheochromocytoma
- preoperative preparation of patients for resection of pheochromocytoma
Reserpine mechanism and uses
irreversibly damages VMAT (vesicles cannot store NE and dopamine); MAO free to degrade NE in the cytoplasm

- gradual decrease in blood pressure and slowing of cardiac rate
Guanethidine mechanism and use
displaces NE from transmitter vesicles leading to depletion of NE

- antihypertensive (causes a gradual decrease in bp and heart rate)

* additionally, the drug inhibits release of NE <-- primarily responsible for its antihypertensive action