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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
Q

What is the mechanism of action of prazosin?

A

Selectively blocks A1 receptors, competitive antagonist

26
Q

What are the effects of Prazosin?

A

Decreases vascular tone (dec BP), favorable lipid profile -> low LDL and high HDL

27
Q

Why is Prazosin preferred over phentolamine or phenoxybenzamine for treating HTN?

A

Fewer side effects. A1 selective blockers (prazosin) has little effect on A2 blockers leading to less side effects of reflex tachycardia

28
Q

What are the therapeutic uses of prazosin?

A

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
Q

What are the side effects of prazosin? How are some of them counteracted?

A

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
Q

What is the mechanism of action of tamsulosin?

A

A1 receptor antagonist (some selectivity of A1a over A1b

31
Q

What are the effects of tamsulosin?

A

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
Q

What are the clinical uses of tamsulosin?

A

Benisn Prostatic Hyperplasia (BPH)

33
Q

What is the mechanism of action of propranolol?

A

competitive reversible block of B1 and B2 receptors

34
Q

What are the therapeutic uses of propranolol? (6)

A

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
Q

What are the side effects of propranolol?

A

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
Q

What conditions should be considered before prescribing propranolol?

A 
Asthma
Congestive heart failure
bradyarrhythmias, AV block
insulin-dependent diabetes prone to hypoglycemic episodes
hypotention
vasospactiv angina
37
Q

What is the route of administration of propranolol?

A

orally available, but lg first pass effect so need to give in high doses

38
Q

What is the route of administration of timolol?

A

orally active

39
Q

What are the therapeutic uses of timolol?

A

Same as propranolol

Additional use for acute wide angle glaucoma

40
Q

What is the mechanism of action of timolol?

A

Non selective beta receptor antagonist - competitive, reversable

41
Q

Explain how timolol can treat glaucoma.

What will timolol do to pupil size and accommodation?

A

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
Q

What are the potential side effects of ophthalmic timolol adminstration>

A

Small amounts can be absorbed into the system leading to other non-selective beta blocking effects -> care with pts with cardiac diseases

43
Q

What is the mechanism of action of metoprolol?

A

B1 selective reversible antagonist, competitive

44
Q

What is the selectivity of metoprolol? Which dose (high vs low) has better selectivity?

A

Selective to B1, but will bind B2 1/10

More selective at low doses

45
Q

What are the major therapeutic uses of metoprolol?

A

Same as propronol

Heart Failure

46
Q

What is the reasoning behind using metoprolol as heart failure treatment?

A

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
Q

What are the side effects of metoprolol?

A

Same as propranolol

Less bronchioconstriction at lower doses

48
Q

What is the mechanism of action of atenolol?

A

B1 receptor antagonist

49
Q

What are the therapeutic uses of atenolol?

A

Similar to propranolol, except for migraine prophylaxis

50
Q

How is atenolol different than propranolol? Significance?

A

Atenolol does not penetrate into CNS -> restricted to periphery
Fewer side effects (especially drowsiness) and longer duration of action

51
Q

What is the mechanism of action of Labetaolol?

A

Competitive antagonist of A1 and B1, and B2 receptors. (non-selective)

52
Q

What are the therapeutic uses of labetanol, and for each what is the route of administration?

A

Essential hypertension - oral

hypertensive emergencies -> IV

53
Q

What is the mechanism of action of carvedilol?

A

Non selective beta blocker, A1 antagonist too -> all competitive

54
Q

What are some additional effects of carvedilol?

A

anti-oxidant properties
anti-inflammatory efects
blocks L-type Ca++ channels at higher doses

55
Q

What are the therapeutic uses of carvedilol?

A

Chronic heart failure, hypertension, acute MI

Pharmacology Block 1 (8 decks)

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