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S2 Case 6 - stroke & anticoagulation > Drug Case: Digoxin > Flashcards

Drug Case: Digoxin Flashcards

1
Q

What class of drug is digoxin?

A

Cardiac glycoside

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2
Q

What is it licensed for?

A

HF
Arrhythmias

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3
Q

What HF is it licensed for?

A

Left ventricular function impaired
= backlog
= leakage of fluid

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4
Q

What arrythmias is it licensed for?

A

Rate control in AF

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5
Q

What is normally used to control rate?

A

BB

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6
Q

How many mechanisms is there for digoxin?

A

2

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7
Q

What is the 1st mechanism?

A

Increase force of myocardial contraction
= positive inotrope

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8
Q

What is the 2nd mechanism?

A

Decrease conductivity at AVN
= negative inotrope

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9
Q

When it is a positive inotrope?

A

Providing symptom benefit in HF

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10
Q

When is it a negative inotrope?

A

Effective rate control in arrhythmias

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11
Q

Why is a loading dose required?

A

Long t1/2

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12
Q

How is rapid digitalisation administered?

A

In divided doses = 50% dose initial + 2md dose 4-8hrs
= this allows distribution to occur + monitor patient for signs of toxicity

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13
Q

How is maintenance for AF + HF given?

A

Orally

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14
Q

How is EMERGENCY loading given?

A

Intravenous infusion
= given slowly over 2hrs

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15
Q

What do you do after IV loading?

A

Give digoxin oral ASAP

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16
Q

What is the normal maintenance dose for AF?

A

125-250mcg

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17
Q

What is the normal maintenance dose for HF?

A

62.5-125mcg

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18
Q

What is digoxin available as?

A

Tablet
Elixir
IV

19
Q

What is the bioavailability of tablet?

A

63%

20
Q

What is the bioavailability of elixir?

A

75%

21
Q

In arrhythmias what can toxicity result in?

A

Formation of ventricular extrasystoles

22
Q

What do you NOT want to go below bpm wise?

A

60bpm

23
Q

What must you check first before starting digoxin?

A

Thyroid
= need a lower dose if hyperthyroidism

24
Q

What is the main problem with digoxin?

A

Narrow therapeutic window

25
Q

What are the therapeutic level?

A

1-2 mcg/L
= >2 TOXIC

26
Q

When do you take the blood?

A

6hrs post dose

27
Q

How many phase distribution is digoxin?

A

2

28
Q

Describe the phase distribution of digoxin

A

Phase 1 = digoxin in serum conc
Phase 2 = digoxin conc in myocardium
Takes 6hrs to reach phase 2

29
Q

How is digoxin structure related to its function?

A

Lots of OH in structure
= mostly renally excreted

30
Q

Because it’s renally excreted what do you need to check?

A

Renal function
= risk of accumulation

31
Q

What does hypokalaemia do?

A

Sensitises myocardium to actions of cardiac glycosides

32
Q

What are the signs of digoxin toxicity?
SLOW AND SICK

A

Bradycardia
Abdominal pain
Blurred or yellow tint vision
Confusion
Rash

33
Q

Can you still be toxic and within the range?

A

YES

34
Q

If you can be toxin + within the range, what does this mean?

A

Always treat the patient, NOT the number

35
Q

How do you treat digoxin toxicity?

A

STOP digoxin
Correct electrolyte balance
DIGFab

36
Q

What is DIGFab?

A

Digoxin-specific Ab FAB fragments

37
Q

How is DIGFab given?

A

IV bolus

38
Q

When do you use DIGFab?

A

If toxic + plasma levels are >3mcg/L
OR patient presents with hypokalaemia or bradycardia

39
Q

What are the interactions?

A

Medicines that…
Cause hypokalaemia
Increase plasma conc
Decrease plasma conc
Decrease excretion

40
Q

What is an example of medicine that increases plasma conc?

A

Enzyme inhibitors

41
Q

What is an example of medicine that decreases plasma conc?

A

Enzyme inducers

42
Q

What is an example of a medicine that decreases excretion?

A

Nephrotoxic medicines

43
Q

What are medicines that should not be considered with digoxin?
CRASED

A

CCB
Rifampicin
Amiodarone
St Johns Wort
Erythromycin
Diuretics

S2 Case 6 - stroke & anticoagulation (7 decks)

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