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Pharmacology Block 1 > Adrenergics - Antagonists > Flashcards

Adrenergics - Antagonists Flashcards

1
Q

What is the general mechanism for an adrenergic neuron blocker?

A

Disrupts the synthesis, storage, or release of NE (does not block receptor)

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2
Q

What is the mechanism of action of guanethidine?

A

Taken into adrenergic nerves via NET -> ultmately causes decrease of NE via unknown mechanism

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3
Q

What is guanethidine used to treat?

A

Severe hypertension

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4
Q

What are the side effects of guanethidine?

A

Many side effects -> orthostatic hypotension, interfere with sexual function, diarrhea, muscle weakness, edema

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5
Q

What is significant about the chemical structure of guanethidine?

A

It is polar -> doesn’t enter the CNS

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6
Q

What is the site of action of guanethidine?

A

PNS

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7
Q

What is Guanadrel?

A

Drug very similar to Guanethidine

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8
Q

What is the mechanism of action of Reserpine?

A

Diffuses into adrenergic nerves -> inhibits VMAT2 -> prevents NE uptake into granules -> prevents NE release

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9
Q

What are the effects of Reserpine?

A

prevent release of NE

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10
Q

What is the significance of reserpine being lipophilic (2)?

A

Gets into CNS -> acts on CNS

diffuses into nerves, doesn’t need transporter, has no effect on NET

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11
Q

What is the route of administration of Reserpine?

A

orally

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12
Q

What are the therapeutic uses of reserpine?

A

essential hypertention -> decreases BP

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13
Q

What are the side effects of reserpine?

A

Sedation, diarrhea, orthostatic hypotention, increased gastric acid secretion, depression, suicidal tendencies

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14
Q

What is the relative half life and onset of reserpine?

A

Long-acting, slow onset

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15
Q

What is an adrenergic receptor blocker?

A

agent that produces its major action by inhibiting A and B receptors

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16
Q

What is the mechanism of action of Phenoxybenzamine?

A

block A1 and A2 receptors

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17
Q

How does phenoxybenzamine block receptors?

A

Irreversible antagonist - binds covalently to A1 and A2 receptors

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18
Q

What is the route of administration and duration of action of phenoxybenzamine?

A

orally, long duration of action b/c of irreversible binding -> new receptors have to be synthesized

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19
Q

What are the effects of phenoxybenzamine and phentolamine?

A

vasodilation (blocking A1 prevents binding of NE to smooth muscle receptors, preventing contraction, blocking A2 on pre-synaptic nerve terminals causes increase NE release b/c loss of negative feedback)

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20
Q

What are the side effects of phenoxybenzamine and phentolamine?

A

With non selective alpha blockers when the antagonist binds A2 on the pre-synaptic nerve terminal, loss of negative feedback occurs. This causes the cell to release lots of NE, and since it has nowhere to bind it binds B1 receptor on cardiac muscle. -> tachycardia, edema, orthostatic hypotention

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21
Q

What are the clinical uses of phenoxybenzamine?

A

Phenochromocytoma, to reverse or shorten the effects of soft-tussue anesthesia from a local anesthetic

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22
Q

What is the mechanism of action of phentolamine?

A

Competitive reversable antagonist to A1 and A2 recpetors

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23
Q

What is the route of administration and duration of action of phentolamine?

A

orally active, shorter duration (2-4 hours)

24
Q

What are the clinical uses of phentolamine?

A

hypertension - in combination with other agents, pheochromocytoma, reduce the effects of local anesthetic

25
What is the mechanism of action of prazosin?
Selectively blocks A1 receptors, competitive antagonist
26
What are the effects of Prazosin?
Decreases vascular tone (dec BP), favorable lipid profile -> low LDL and high HDL
27
Why is Prazosin preferred over phentolamine or phenoxybenzamine for treating HTN?
Fewer side effects. A1 selective blockers (prazosin) has little effect on A2 blockers leading to less side effects of reflex tachycardia
28
What are the therapeutic uses of prazosin?
HTN, short term treatment of CHF -> preload and afterload reducing agent, BPH -> relaxes A1 mediated contraction of prostate and bladeder neck that contributes to resistance in urine flow meaning it makes it easier to pee
29
What are the side effects of prazosin? How are some of them counteracted?
First dose phenomenon -> hypotention and syncope 30-90 min after first dose -> give first dose at bedtime persistent orthostatic hypotention edema (salt and water retention)
30
What is the mechanism of action of tamsulosin?
A1 receptor antagonist (some selectivity of A1a over A1b
31
What are the effects of tamsulosin?
blocks A1a receptors (prostate) which decreases tone in prostate and neck of bladder -> easier to urinate Has little effect on hypertension b/c A1b receptors aren't generally blocked
32
What are the clinical uses of tamsulosin?
Benisn Prostatic Hyperplasia (BPH)
33
What is the mechanism of action of propranolol?
competitive reversible block of B1 and B2 receptors
34
What are the therapeutic uses of propranolol? (6)
Hypertension - block b receptors in hear and kidney Angina -> decrease work of heart and energy demand Cardiac arrhythmia due to excess catecholamines or that respond do a reduction in HR/AV conduction velocity Acute MI Pheochromocytoma Migrane prophylaxis
35
What are the side effects of propranolol?
Cardiac depression, heart block increased airway resistance (b/c blockage of B2) Can mask symptoms of hypoglycemia Sedation, impotence, nightmares Can have withdrawl syndrome with can cause arrhythmias or infarction
36
What conditions should be considered before prescribing propranolol?
``` Asthma Congestive heart failure bradyarrhythmias, AV block insulin-dependent diabetes prone to hypoglycemic episodes hypotention vasospactiv angina ```
37
What is the route of administration of propranolol?
orally available, but lg first pass effect so need to give in high doses
38
What is the route of administration of timolol?
orally active
39
What are the therapeutic uses of timolol?
Same as propranolol | Additional use for acute wide angle glaucoma
40
What is the mechanism of action of timolol?
Non selective beta receptor antagonist - competitive, reversable
41
Explain how timolol can treat glaucoma. | What will timolol do to pupil size and accommodation?
With opthalmic administration -> beta blocker decreases aqueous humor formation (b/c b2 antagonist) by the cillary epithelium -> less fluid -> less interocular pressure No effect on pupil size or accommodation -> no blurred vision, no night blindness
42
What are the potential side effects of ophthalmic timolol adminstration>
Small amounts can be absorbed into the system leading to other non-selective beta blocking effects -> care with pts with cardiac diseases
43
What is the mechanism of action of metoprolol?
B1 selective reversible antagonist, competitive
44
What is the selectivity of metoprolol? Which dose (high vs low) has better selectivity?
Selective to B1, but will bind B2 1/10 | More selective at low doses
45
What are the major therapeutic uses of metoprolol?
Same as propronol | Heart Failure
46
What is the reasoning behind using metoprolol as heart failure treatment?
By blocking B1 receptors selectively there is less stress on the heart. Been proven that continuous sympathetic activation of beta receptors will cause progression of the disease
47
What are the side effects of metoprolol?
Same as propranolol | Less bronchioconstriction at lower doses
48
What is the mechanism of action of atenolol?
B1 receptor antagonist
49
What are the therapeutic uses of atenolol?
Similar to propranolol, except for migraine prophylaxis
50
How is atenolol different than propranolol? Significance?
Atenolol does not penetrate into CNS -> restricted to periphery Fewer side effects (especially drowsiness) and longer duration of action
51
What is the mechanism of action of Labetaolol?
Competitive antagonist of A1 and B1, and B2 receptors. (non-selective)
52
What are the therapeutic uses of labetanol, and for each what is the route of administration?
Essential hypertension - oral | hypertensive emergencies -> IV
53
What is the mechanism of action of carvedilol?
Non selective beta blocker, A1 antagonist too -> all competitive
54
What are some additional effects of carvedilol?
anti-oxidant properties anti-inflammatory efects blocks L-type Ca++ channels at higher doses
55
What are the therapeutic uses of carvedilol?
Chronic heart failure, hypertension, acute MI

Pharmacology Block 1 (8 decks)

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