Beta Blockers Flashcards

1
Q

Beta blocker indications

A
Hypertension
Angina
HF
Arrhythmia (AF, A. flutter, SVT)
Thyrotoxicosis
Migraine prophylaxis
Anxiety
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2
Q

Where are B1 receptors found?

A

Heart

Kidneys

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3
Q

Where are B2 receptors found?

A

Blood vessels
Bronchi
Kidneys

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4
Q

B-blocker mechanism of action

A

Antagonise post-synaptic B-adrenoreceptors with varying selectivity
Connected to cAMP pathway which initiates NE release

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5
Q

Commonly used B-blockers and their selectivity

A

Metoprolol – B1
Atenolol – B1
Propanolol – B1/2
Labetalol – B1/2 + alpha (used in pregnancy)

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6
Q

Water soluble B-blockers

A

E.g., atenolol

Excreted via kidneys, long half life

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7
Q

Lipid soluble B-blockers

A

E.g., propanolol, metoprolol

Metabolised by liver, short half life. Can be encapsulated to prolong metabolism.

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8
Q

B-blocker pharmacokinetics

A
Well-absorbed orally
Sustained release preparations available
Some IV preparations
Variable lipophilicity
More lipophilic = better at crossing BBB
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9
Q

Effects of B-blockers on CNS

A
Lower BP
- Reduce CO
- Reset baroreceptors
- Renin inhibition
- Direct sympathetic activity reduction
Negatively chronotropic
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10
Q

Inotropic effects of B-blockers

A

Acute: negative
Long-term: positive
Therefore can be used carefully in HF patients to improve condition, but can worsen fluid overload and decrease contractility if given acutely

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11
Q

Respiratory effects of B-blockers

A

B2 receptor antagonism therefore contraindicated in asthmatics

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12
Q

Eye effects of B-blockers

A

Reduce aqueous humour production, give topically

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13
Q

Metabolic effects of B-blockers

A

Decrease gluconeogensis via B2 receptors

Slow down hypoglycaemia resolution and mask some symptoms of hypoglycaemia therefore care must be taken in diabetics

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14
Q

Thyroid effects of B-blockers

A

T4- —> T3 conversion under control of B receptors therefore can inhibit T3 production and relieve thyrotoxicosis symptoms
Use propanolol

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15
Q

Adverse effects of B-blockers

A
Asthma exacerbation
Hypotension
Bradycardia
Vasospasm
Fatigue
Impotence
Nightmares
Withdrawal
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16
Q

How do B-blockers cause withdrawal?

A

Long-term use can upregulate post-synaptic receptors therefore slow retraction of drug necessary

17
Q

B-blocker interactions

A

Contraindicated with verapamil (marked negative chronotropic effect)
Diltiazem (caution but acceptable)
Other BP lowering drugs
Antidiabetics (hypoglycaemia awareness)

18
Q

B-blockers in angina

A

Reduce heart rate and cardiac work

Metoprolol and atenolol

19
Q

B-blockers post-MI

A

Decrease arrhythmia
Decrease ventricular rupture
Increase cardiac remodelling

20
Q

B-blockers in heart failure

A

In the damaged heart, the ratio of receptors shifts, increasing the relative proportions of B2 and a1 receptors, therefore carvedilol, a mixed B/a antagonist/antioxidant is a good choice, or metoprolol (B1)

21
Q

B-blockers and hypertension

A

Not 1st choice, but if patient also has AF and/or HF, should be considered
Metoprolol