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*Y2 LCRS Pharmacology* > SNS Antagonists > Flashcards

SNS Antagonists Flashcards

1
Q

What does α1 Adrenoceptor do?

A

Vasoconstriction, Relaxation of GIT

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2
Q

What does α2 Adrenoceptor do?

A

Inhibition of transmitter release, contraction of vascular smooth muscle, CNS actions

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3
Q

What does β1 adrenoceptor do?

A

Increased cardiac rate and force, relaxation of GIT, renin release from kidney

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4
Q

What does β2 ​adrenoceptor do?

A

Bronchodilation, vasodilation, relaxation of visceral smooth muscle, hepatic glycogenolysis

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5
Q

What does β3 ​adrenoceptor do?

A

Lipolysis

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6
Q

How does α2 receptor-mediated negative feedback work?

A

NA released from synapse can bind to α2 receptor on the presynaptic bulb. This reduces synthesis and release of NA from the synapse

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7
Q

Name a non-selective adrenoceptor antagonist:

A

Carvedilol

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8
Q

Name an α adrenoceptor selective antagonist:

A

Phentolamine (α1+2)

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9
Q

What does Prazosin selectively antagonise?

A

α1

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10
Q

Name a β adrenoceptor selective antagonist:

A

Propanolol (β1+2)

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11
Q

What receptor does Atenolol antagonise?

A

β1

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12
Q

What are the main clinical uses of Adrenoceptor antagonists?

A

Hypertension

Cardiac Arrhythmias

Angina

Glaucoma

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13
Q

What is the definition of Hypertension, and what are the factors that contribute to it?

A

Sustained diastolic blood pressure greater than 90mmHg

(NICE: <140/90mmHg)

Blood Volume

Cardiac Output

Total Peripheral Resistance

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14
Q

What are the sympathetic controls of Blood pressure?

A

Controls heart via β1 receptors

Main controller: Renin release from kidneys via β1

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15
Q

What tissues can anti-hypertensives target?

A

The heart - cardiac output

Sympathetic nerves that release the vasoconstrictor noradrenaline

The kidney - blood volume/vasoconstriction

Arterioles - peripheral resistance

The brain - blood pressure set point

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16
Q

Which organs do beta-blockers target?

A

The heart and kidneys (β1)

Sympathetic nerves and CNS (β1 + 2)

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17
Q

How do beta-blockers work on the heart to lower BP?

A

Reduce HR and CO via β1 but this effect disappears with chronic treatment as the heart resets itself

18
Q

How do beta-blockers work on the kidney to decrease HR?

A

β1 antagonism reduces renin production which results in decreased TPR

This leads to reduced production of Angiotensin II a potent vasoconstrictor

19
Q

How do beta-blockers act on presynaptic β-adrenoceptors?

A

Blockade of the facilitatory effects (positive feedback) of presynaptic β-adrenoceptors on noradrenaline release may also contribute to the antihypertensive effect.

20
Q

What are cardioselective beta-blockers?

Name one

A

More selective for β1 receptors

Atenolol

21
Q

What are mixed β-α blockers?

(I would rather die lol)

A

Carvedilol - a1 blockade gives additional vasodilator properties

22
Q

What is Nebivolol?

A

A β1 blocker that also potentiates NO

23
Q

What is Sotalol?

A

A β-blocker that also inhibits K+ channels

24
Q

What is the main side-effect of beta-blockers?

What group of patients must you therefore be careful when prescribing to?

A

Bronchoconstriction - Asthma/COPD can be dramatic and life-threatening

25
Q

What are the two other main serious side-effects of Beta-blockers?

A

Cardiac Failure - need some sympathetic drive to the heart

Hypoglycemia - The use of b-antagonists mask the symptoms of hypoglycemia (sweating, palpitations, tremor). Use of non-selective b-antagonists are more dangerous in such patients since they will also block the b2- receptors driven breakdown of glycogen . b1- selective agents may have advantages since glucose release from the liver is controlled by b2- receptors.

26
Q

What are three less serious side-effects of beta-blockers?

A

Fatigue - less cardiac output and less muscle perfusion.

Cold Extremities - Loss of β-receptor-mediated vasodilatation in cutaneous vessels.

Bad Dreams

27
Q

What us the main advantage of Atenolol over propranolol?

A

Atenolol β1 selective

Propanolol β non-selective

Decreased side effects with Atenolol as they tend to be due to β2 receptors, however they are not fully selective so some side-effects may remain

28
Q

What is the advantage of Carvedilol over Atenolol?

A

In reducing BP, both reduce Renin secretion and contractility, but Carvedilol also reduces vasoconstriction and therefore TPR due to alpha1 blockade

29
Q

How do α1 receptors work?

A

Gq linked receptors

30
Q

How do α2 receptors work?

A

Gi linked receptors

31
Q

What is prazosin and how does it work?

A

Highly selective α1 antagonist

Hypotensive via inhibition of vasoconstriction

Also causes decrease in LDLs and increase in HDLs

32
Q

What is Phentolamine and how does it work?

A

Non-selective α antagonist

Hypotensive via inhibition of alpha mediated vasoconstriction

Also blocks presynaptic α2 inhibitory effects so increased NA which enhances reflex tachycardia

33
Q

What are the side-effects of α-blockers?

A

Postural Hypotension - when you stand up SNS kicks in to give boost to BP, which is blocked

Reflex Tachycardia

Increased GIT motility

34
Q

Why does phentolamine have reduced effectiveness due to α2 receptors?

A

Blocks α2 inhibitory effect, so there is an increase in NA release which enhances the reflex tachycardia

35
Q

What does methyldopa create?

A

A false-transmitter - alpha-methylnoradrenaline

36
Q

How do false-transmitters work to reduce hypertension?

A

Methylnoradrenaline displaces NA from synaptic vesicles

Far less active on α1 receptors than NA therefore less effective at causing vasoconstriction

It is also more active on α2 receptors reducing NA release

37
Q

What are the side-effects of Methyldopa?

A

Dry mouth, sedation, Orthostatic hypotension, Male sexual dysfunction

38
Q

Why are Beta-blockers given to patients with arrhythmias?

A

An increase in sympathetic drive to the heart via b1 can precipitate or aggravate arrhythmias. Particularly after myocardial infarction there is an increase in sympathetic tone.

AV conductance also depends critically on sympathetic activity, and the refractory period of the AV node is increased by b-adrenoceptor antagonists, interfering with AV conduction in atrial tachycardia’s, and to slow ventricular rate.

Reduce heart rate so reduces the severity of arrhythmias

39
Q

How do beta-blockers reduce angina?

A

Angina is pain that occurs when O2 supply to myocardium is insufficient

At low doses, b1-selective agents, metoprolol, reduce heart rate and myocardial contractile activity without affecting bronchial smooth muscle.

O2 demand is reduced whilst the same degree of effort is maintained

40
Q

How do beta-blockers treat glaucoma?

A

They reduce the production of Aqueous humour by blocking the receptors on the ciliary body

*Y2 LCRS Pharmacology* (20 decks)

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