DIGOXIN

Question 1

Drug class

Answer 1

cardiac glycoside

Question 2

What does negatively chronotropic mean?

Answer 2

reduces heart rate

Question 3

What does positively inotrophic mean?

Answer 3

increases contractility

Question 4

What does digoxin do? (2)

Answer 4

1. It is negatively chronotropic - reduces heart rate

2. and is positively inotrophic - increases contractility

Question 5

How does digoxin work in atrial fibrillation and atrial flutter? (5)

Answer 5

• via indirect pathway
• increasing vagal (parasympathetic) tone
• this reduces conduction at the AVNode
• this prevents impulses from being transmitted to the ventricles
• this consequently reduces ventricular rate

Question 6

How does digoxin work in heart failure? (6)

Answer 6

• has a direct effect on myocytes
• by inhibiting Na/K/ATPase pumps
• this causes Na to accumulate in the cell
• cellular extrusion of Ca2+ required low intracellular Na+ conc
• elevation of intracellular Na causes Ca2+ to accumulate
• this increases contractile force

Question 7

Indications (2)

Answer 7

1. atrial fibrilation

2. severe heart failure - 3rd line treatment

Question 8

Contra-indications (5)

Answer 8

1. heart

• second heart block
• intermittent complete heart block
• ventricular arrhythmias

2. kidneys
   - renal failure

ION IMBALANCES

3. HYPOKAELEMIA
   - digoxin competes with K in Na/K pump
4. hypomagnaesemia
5. hypercalcaemia

Question 9

Side effects (4)

Answer 9

1. heart
   - bradycardia
   - arrhythmias
2. GI upset
3. Skin
   - Rash
4. Head
   - dizzy
   - visual disturbances

Question 10

Interactions (5)

Answer 10

1. loop diuretics

• increases digoxin toxicity
• due to hypokaelemia

2. amiodarone
3. calcium channel blockers
4. spironolactone
5. quinine

• increases the plasma concentrations of digoxn
• digoxin toxicity

Question 11

Elimination

Answer 11

kidneys