CARDIOVASCULAR CASE STUDY 1

Question 1

What effect does digoxin have on the failing heart?

Answer 1

Increased cardiac output, increased stroke volume

Question 2

What is the mechanism of action of digoxin?

Answer 2

• blocks Na+/K+ pump on cardiac myocyte
• causing an increase in intracellular Na+
• Na cannot feed into Na+/Ca2+
• causing an increase in intracellular Ca2+
• increased Ca2+ allows greater activation of the contractile elements and increased force of heart contraction

Question 3

What are the side effects of digoxin?

Answer 3

Induction of arrythmia, disorientation, hallucinations, gastrointestinal upset

Question 4

Explain the toxicity and therapeutic window of digoxin relative to a drug such as
penicillin

Answer 4

Digoxin - narrow therapeutic window, difference between therapeutic and toxic dose is minimal

Penicillin - wider therapeutic window, it is much harder to achieve a toxic dose

Question 5

What safer alternatives could be prescribed instead of digoxin?

Answer 5

Beta blockers or calcium channel blockers