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Pharmacology > Pharm 8 - SNS Antagonists > Flashcards

Pharm 8 - SNS Antagonists Flashcards

1
Q

Describe the effects of Alpha 1 adrenoceptors.

A

Vasoconstriction

GI tract relaxation

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2
Q

Describe the effects of Alpha 2 adrenoceptors.

A

Inhibition of transmitter release

contraction of vascular smooth muscle

CNS actions

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3
Q

Describe the effects of beta 1 adrenoceptors.

A

Heart - increased heart rate + contractility
Kidneys - increased renin release
GI tract relaxation

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4
Q

Describe the effects of Beta 2 adrenoceptors.

A

Bronchodilation
Vasodilation
Relaxation of visceral smooth muscle
Hepatic glycogenolysis

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5
Q

Describe the effects of Beta 3 adrenoceptors.

A

Lipolysis

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6
Q

State 5 adrenoceptors antagonists and the receptors they block.

A 
Labetalol = alpha 1 + beta 1 (more beta 1 (4:1))
Phentolamine = alpha 1 + alpha 2
Prazosin = alpha 1
Propranolol = beta 1 + beta 2
Atenolol = beta 1
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7
Q

State 4 main clinical uses of SNS antagonists.

A

Hypertension
Angina
Arrhythmia
Glaucoma

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8
Q

What is defined as hypertension?

A

Sustained diastolic blood pressure greater than 90mmHg

or greater than 140/90

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9
Q

State the 3 things which contribute to hypertension.

A

Blood volume
Cardiac output
Peripheral vascular tone

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10
Q

What is the main control of blood pressure?

A

Sympathetic drive to the kidneys via beta 1

this triggers renin release from the kidneys causing increase in angiotensin II and aldosterone

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11
Q

Blockade of which receptors cause the positive and negative effects of beta blockers.

A

blockade of b1 = positive effects

blockade of b2 = negative effects

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12
Q

What effect is responsible for most of the anti-hypertensive effect of beta blockers?

A

b1 blockade in the kidneys leading to reduced renin release

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13
Q

What effect does beta 1 blockade have on the heart?

A

decrease in heart rate

decrease in cardiac output

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14
Q

How does the effect of beta blockers on the heart change with prolonged treatment?

A

reduced efficacy as heart begins to reset itself

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15
Q

What is the effect of presynaptic beta 1 receptors?

A

have a positive facilitation effect on the synthesis and release of a neurotransmitter

so blockade of this adds to the antihypertensive effect

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16
Q

State 4 conditions in which you would not give a patient a beta blocker.

A

1) Asthma - blockade of beta 2 will cause bronchoconstriction
2) Cardiac failure - rely on SNS input to have adequate cardiac output
3) COPD - bronchoconstriction via beta 2 blockade
4) Diabetes - masks the symptoms of hypoglycaemia + inhibits hepatic glycogenolysis

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17
Q

State 2 side effects of beta blockers.

A

Fatigue

Cold extremities

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18
Q

Why would you still not give a cardioselective beta blocker to an asthmatic?

A

selectivity is based on concentration

19
Q

What are the effects of labetalol?

A

acts more on beta 1 than alpha 1
lowers blood pressure by reducing TPR via alpha 1

reduces heart rate and contractility via b1 blockade

20
Q

What is the main mediator of TPR?

A

Alpha 1 mediated vasoconstriction

21
Q

What are the effects of an alpha blocker?

A

vasodilation causing a fall in TPR and hence a fall in blood pressure

22
Q

What is the main side effect of alpha blockers?

A

Postural hypotension

reflex tachycardia via baroreceptors

23
Q

State some of the problems with non-selective alpha blockers ?

A

alpha 1 blockade will cause vasodilation and decrease in TPR

blockade of alpha 2 will cause INCREASE in transmitter release, so more noradrenaline released

this would enhance reflex tachycardia

24
Q

What are the effects of prazosin - alpha 1 antagonist?

A

leads to vasodilation and fall in TPR

get less tachycardia as not losing inhibitory alpha 2

25
Describe the mechanism of action of methyldopa.
Methyldopa is taken up by noradrenergic neurones and is decarboxylated and hydroxylated for form alpha-methyl noradrenaline This is not deaminated by MAO so accumulates more than noradrenaline in the synapse Alpha-methyl noradrenaline displaces NA from the synaptic vesicles It is less effective than NA on alpha 1 receptors so does not cause as much vasoconstriction It is more effective than NA on alpha 2 receptors thus reducing noradrenaline release
26
What are arrhythmias caused by and why?
Myocardial ischaemia
27
What controls the pacemaker current in the heart?
Sympathetic drive
28
What can precipitate or aggravate arrhythmias?
increase in sympathetic drive to the heart via b1
29
What part of the heart's electrical circuit depend on the sympathetic drive?
AV conductance
30
What effect do beta antagonists have on the refractory period of the AV node?
increases the refractory period slows down ventricular rate
31
What class of drugs are beta blockers?
Class II anti-arrhythmics
32
What is propanolol particularly effective at treating?
arrythmias causes by exercise or mental stress
33
Define angina.
chest pain that occurs when oxygen supply to myocardium is insufficient for its needs.
34
Describe the 3 different types of angina.
Stable - pain due to fixed narrowing Unstable - pain with less and less exertion Variable - occurs at rest, caused by coronary artery spasm
35
What is the mechanism of unstable angina?
atheromatous plaque begins to rupture Platelet fibrin thrombus associated with the ruptured plaque high risk of infarction
36
Describe how beta blockers can help prevent angina attacks.
decrease heart rate, contractility and systolic pressure less oxygen demand on the heart so less chance of reaching angina
37
State some adverse side effects of beta blockers.
``` Fatigue Insomnia Dizziness Sexual dysfunction Bronchospasm Bradycardia Heart block Hypotension Decreased myocardial contractility ```
38
State some other circumstances in which you would not give a beta blocker?
hypotension bradycardia congestive heart failure bronchospasm
39
Where is aqueous humour produced?
ciliary body via carbonic anhydrase
40
What dictate the amount of humour produced?
Blood flow in ciliary body
41
Where does the humour drain into?
Trabecular meshwork in the canals of Schlemm
42
How can adrenaline affect intraocular pressure?
can act on alpha 1 receptors to cause vasoconstriction and reduce blood flow through ciliary body
43
Describe the use of beta antagonists in treating glaucoma.
Reduce the rate of aqueous humour produced by blocking receptors on ciliary body
44
State some other used of beta antagonists.
Anxiety Migraine Benign tumours

Pharmacology (10 decks)

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