Drugs

Question 1

Digoxin (Digitalis)

Answer 1

• cardiac glycoside
• positive inotropic effect
  
  • ​inhibits Na+/K+ ATPase within cardiomyocytes –> increased intracellular Na+ –> impedes NCX –> blocks Ca2+ export –> intracellular Ca2+ inceased/maintained –> enchancing contraction
• ​vagomimetic effect
  
  • ​slows SA and AV nodal conduction
  • sensitizes baroreceptors –> increases afferent inhibitory activity which reduces activation of SNS afferents (which up-regulate heart rate and constiction)

Question 2

Diltiazem and Verapamil

Answer 2

• type L Ca2+ antagonists, relatively specific for type L Ca2+ channels expressed in the heart
• slow AV conduction
• negative inotropic effect