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SNS antagonists Flashcards

1
Q

What are the SNS adrenoceptor subtypes and what do they cause to happen?

A

alpha 1- vasoconstriction, relaxation of GIT
alpha 2 - inhibition of transmitter release, contraction of vascular smooth muscle and CNS actions
beta 1 - increased cardiac rate and force, relaxation of GIT and renin release from kidney
beta 2 - bronchodilation, vasodilation, relaxation of visceral smooth muscle, hepatic glycogenolysis
beta 3 - lipolysis

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2
Q

What can neurotransmitters also act as?

A

-auto receptors on the presynaptic membrane that influence the synthesis and release of neurotransmitter

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3
Q

What adrenoceptors does carvedilol favour?

A
  • totally non-selective

- alpha 1 and beta 2

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4
Q

what adrenoceptor does phentolamine favour?

A
  • alpha 1 and -alpha 2

- non-selective

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5
Q

what adrenoceptor does prazosin favour?

A

-alpha 1

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6
Q

what adrenoceptor does propranolol favour?

A
  • beta 1 and beta 2

- non-selective

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7
Q

what adrenoceptor does atenolol favour?

A

-beta 1

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8
Q

what is hypertension defined as?

A

-BP consistently over 140/90 mmHg

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9
Q

what is the most important risk factor for stroke?

A

-hypertension

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10
Q

what is hypertension a high risk factor for?

A
  • chronic kidney disease

- myocardial infarction

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11
Q

what is the equation for blood pressure?

A

BP=CO x TPR

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12
Q

What are the main contributors towards blood pressure?

A
  • cardiac output
  • blood volume
  • vascular tone
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13
Q

What effect do beta blockers have on adrenoceptors?

A
  • block beta 1 receptors on the heart leading to a reduction in HR and force of contraction, leading to reduced BP
  • blocks beta 1 receptors on the kidney, reducing renin production, reducing angiotensinogen II - decreasing peripheral resistance
  • blockade of beta 1 and beta 2 may block noradrenaline release from sympathetic nerves
  • reduces sympathetic tone in the CNS
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14
Q

What are the side effects of beta blockers?

A
  • bronchoconstriction
  • cardiac failure
  • hypoglycaemia
  • fatigue
  • cold extremities
  • bad dreams
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15
Q

what extra property does carvedilol have?

A

-alpha 1 blockade give additional vasodilator properties

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16
Q

what does nebivolol effect?

A
  • it is a beta 1 blocker

- stimulates NO release

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17
Q

what does sotalol effect?

A
  • blocks both beta1 and beta 2

- inhibits K+ channels, interferes with cell hyperpolarisation

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18
Q

what type of patients do you not want to give beta blockers to?

A
  • asthmatic/COPD
  • cardiac failure (these patients rely on a degree of sympathetic drive to maintain adequate CO)
  • diabetic (beta blockers can mask the symptoms of hypoglycaemia e.g. sweating)
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19
Q

Why do you experience fatigue?

A

-reduced CO and reduced muscle perfusion

20
Q

Why do you suffer from cold extremities?

A

-loss of beta receptor mediated vasodilation of cutaneous vessels

21
Q

What are the advantages of propranolol vs atenolol

A
  • atenolol has a reduction of B2side effects

- asthmetics and diabetics are lesslikely tp respond badly to the drug but it is STILL NOT SAFE

22
Q

What advantage does carvedilol have over atenolol and propranolol?

A

-more powerful hypotensive effect - decreases FOC on the heart through B1, blocked renin release on the kidney through B2 and blocks vasoconstriction on vessels through A1

23
Q

What is the mechanism for A1 receptors and where are they found?

A
  • Gq linked
  • PIP2 - IP3 - Ca2+
  • PIP2 - DAG - PKC
  • postsynaptic on vascular smooth muscle
24
Q

What is the mechanism for A2 receptors and where are they found?

A
  • Gi linked
  • ATP - CAMP -PKA
  • presynaptic autoreceptors inhibiting NA release
25
What is phentolamine used for?
-pheochromocytoma- induced hypertension
26
What is prazosin used for?
- inhibits vasoconstrictor activity of NA - modest BP lowering effects - adjunctive treatment
27
How does phentolamine work?
- blocks alpha 1 and alpha 2 (non-selective) - reduced negative feedback from alpha 2 leads to increased release of NA - this competes with the alpha 1 blockade - baroceptors detect dilated blood vessels through decreased vagal activity, sympathetic activity is increased
28
What is an advantage of prazosin over phentolamine?
- less tachycardia occurs as NA release is not increased from the end of nerve terminals - CO decreases due to fall in venous pressure and from dilation of capacitance vessels - hypotensive effect is dramatic - also causes a modest decrease in LDL, increase in HDL
29
Describe how methyldopa works?
- it is taken up by noradrenergic neurons, it is then decarboxylated and hydroxylated to form a false transmitter (a-methyl-noradrenaline) so it cannot be modified by MAO - it accumulates in larger quantities than noradrenaline, displacing it from synaptic vessels
30
How is A-methyl-noradrenaline release?
the same way as noradrenaline
31
what adrenoceptors does AMN act on?
- less effective than NA on alpha 1 so they are less effective causing vasoconstriction - more active on presynaptic alpha 2, reduces NA release below normal - stimulates vasopressor centre in the brain to inhibit sympathetic outflow
32
What other benefits are there of methyldopa?
- used in renal insufficiency or cerebrovascular disease | - advised for an antihypertensive in pregnant women as it has no adverse side effects on the foetus
33
What are the side effects of methyldopa?
-dry mouth -sedation -orthostatic hypotension male sexual dysfunction
34
What is an arrhythmia and what is its main cause?
- abnormal or irregular heartbeat | - myocardial ischemia
35
What increases the chance of an arrhythmia?
exercise
36
What are used for treatment of arrhythmia and why?
- beta blockers - -increase the refractory time of AV node, slowing down ventricular rate- beneficial in the case of atrial tachycardia - this controls sympathetic drive -propranolol, particularly successful in ones that occur during exercise or mental stress
37
What is angina?
-pain when the oxygen supply to the myocardium is insufficient for its needs
38
What causes angina?
-exertion or excitement, mostly by atherosclerosis
39
What are the 3 types of angina?
- stable (pain on exertion) - unstable (pain with less and less exertion) - variable (at rest)
40
What are used to treat anginas and why?
- beta adrenoceptor antagonists - decrease HR, systolic BP and cardiac contractile activity - they will reduce oxygen demand whilst maintaining the same degree of effort -at low dose metoprolol reduces HR and myocardial contractile activity without affecting bronchial smooth muscle
41
What patients are beta blockers not used in to treat angina?
- bradycardic (<55 bpm) - Bronchospasm - Hypotensive - AV block or severe congestive heart failure
42
What is glaucoma?
-increase in intraocular pressure
43
How does fluid normal pass through the eye?
- aqueous humour is produced by blood vessels in the ciliary body via carbonic anhydrase - the amount of humour produced is directly related to the blood flow in the ciliary body - the aqueous humour flows through the posterior chamber, through the pupil and into the anterior chamber - drains into the trabecular meshwork in the canal of schlemm
44
What can adrenaline act on in the eye?
-alpha 1 receptors to cause vasoconstriction and reduce blood flow through the ciliary body
45
What are used to treat glaucoma?
- non selective or selective antagonists - they reduce the rate of aqueous humour formation by blocking receptors on the ciliary body - non selective that work: carteolol hydrochloride, levobunolol hydrochloride, timolol maleate - selective that work: betaxolol hydrochloride
46
WHat other uses of beta antagonists are there?
- anxiety states e..g palpitations and tremor - migraine prophylaxis, maintains a good supply to the CNS - benign essential tumour

Pharmocology (16 decks)

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