Drugs Flashcards

1
Q

What is the Vaughan Williams classification?

A

1- Na channel blockers

2 - Beta blockers

3 - K channel blockers

4 - Ca channel blockers

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2
Q

How do class 1 drugs work?

A

Stabilising the cell membrane via decreased excitogenicity

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3
Q

What do type 1a drugs do? Name an example

A

Slow conduction velocity in both atrial and ventricular cells. Higher doses slows AV conduction. Block K leading to slower repolarisation.
Procainamide

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4
Q

When are type 1a drugs used?

A

Ventricular and atrial arrhythmias especially post MI

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5
Q

What do type 1b drugs do? Example.

A

Reduces AP duration in abnormal ventricular cells. Slows recovery of sodium channels.
Does not shorten effective refractory period

Lignocaine

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6
Q

When are type 1b drugs used?

A

Ventricular arrhythmias post MI or dig toxicity

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7
Q

What do type 1c drugs do? Example

A

Depressants of sodium current. Markedly slows conduction velocity in atria and ventricles.
Increased QRS duration.

Flecainide
Used for refractory arrhythmias

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8
Q

How do beta blockers work?

A

Block cardiac beta receptor response to sympathetic nervous system stimulation.
Decreased G-protein S responses and decreased cAMP.

Also interfere with the binding of epinephrine and other stress hormones ro receptors

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9
Q

B1 receptors are located in?

A

The heart and kidneys

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10
Q

B2 receptors are located in?

A

Lungs, GI, liver, uterus, smooth muscle, skeletal muscle

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11
Q

How do B blockers affect action potential

A

Decreased rate of phase 4 depolarisation + slows SA node rate.

Prolonged PR on ecg

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12
Q

How do potassium channel blockers affect the AP?

What is an example?

A

Prolongs by blockade of K - aka lengthed repolarisation

Amiodarone

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13
Q

Potassium blockers do what to the refratory period?

A

Increase in the effective refractory period

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14
Q

What can potassium channel blockers cause?

A

Torsades, by QT prologation

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15
Q

Amiodarone affects atrial or ventricular tissues?

A

Both, including AV node and SA node

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16
Q

Half life of amiodarone?

17
Q

Which receptors does amiodarone work on?

A

Beta

Potassium

Sodium

Calcium

18
Q

What are the effects of amiodarone?

A

Slow AV and SA node conduction

Increased refractory period

Slowed intracardiac AP conduction

19
Q

Side effects of amiodarone?

A

Interstitial lung disease

Hyper/hypothyroid

Corneal microdeposits

Jaundice/hepatitis

Blue grey skin discolouration

Peripheral neuropathy

Epididymitis

Gynaecomastia

20
Q

When is amiodarone contraindicated?

A

Pregnancy + breast feeing

Sinus node bradycardia

AV block

2/3rd degree HB

21
Q

How does digoxin work?

A

Inhibits Na/K ATPase of cell membrane

This increases intracellular sodium levels, reverses sodium-calcium exchanger, increases intracellular calcium and therefore increases myocardial contraction

22
Q

How is the baro-receptor effected by digoxin?

A

Improves baroreceptor sensitivity by inhibition of sodium pump

23
Q

Cardiac effects of digoxin?

A

Increased ventricular ejection, decreased ED size, higher CO, increased renal perfusion

24
Q

How does it affect sthe autonomic nervous system?

A

Decreases symp. Increases parasymp via vagus (AV node delay)

25
How does digoxin affect the refractory period?
Increases in the SA and AV nodes. Decreased in atria and ventricles
26
Side effects of digoxin?
Anorexia, N/V, diarrhoea, blurred vision, confusion, drowsiness, dizziness, insomnia, agitation, depression. Rare - psychosis, delirium, amnesia, convulsions Shortened QRS, A or V extrasystoles, VF/VT, heart block, paroxysmal atrial tachycardia with AV block
27
How does digoxin affect the ecg?
Increased PR, decreased QT, flattened T waves. Can cause AV junctional rhythm and ectopics
28
How does adenosine work?
Affects A1 adenosine receptors in SA and AV. Inhibits adenylyl cyclase, reducing cAMP -\> cell hyperpolarisation
29
How does high dose adenosine work?
Hyperpolarisation through outward potassium flux and reduced calcium current leading to a temporary block in conduction Also causes vascular dilation
30
Side effects of adenosine
Facial flushing, chest rash, light headedness, diaphoresis, nausea, metallic taste
31
When is adenosine contraindicated?
2nd/3rd degree HB sick sinus syndrome Long QT severe hypotension Decompensated HF Asthma Drug induced tachycardia
32
What % of body magnesium is in heart and smooth muscle
35%
33
What are the effect of Mg
Inhibits acetylcholine and noradrenaline release. Antagonises NDMA
34
How does Mg affect the cell membrane?
Stabilises it via acting as a cofactor for Na/K ATPase. Is bound to cellular ATP
35
What are the effects of Mg on cardiac tissue?
Prolongs sinus node recovery, reduced automaticity and AV node/His conduction
36
What does low Mg cause in patients with myocardial ischaemia?
Facilitates Ca2 influx, which causes cellular death