Digoxin as an inotrope

because this is a specific curriculum item for some reason hey ho

Uses:
Mechanism of action inhibition of Na/K ATPase
Dose loading...
maintenance
Pharmacokinetics Absorption
Distribution
Metabolism
Elimination renal; t 1/2 36h
Time course of action Onset IV 5-30 min; PO 30 min - 2h
Adverse effects Common: dizziness, blurred vision, conduction disorder (bigeminy, trigeminy, PR prolongation); N+V, diarrhoea, rash

Very rare (but comes up in question banks for some reason): gynaecomastia???, thrombocytopenia, psychosis, SVT, ST depressoin ????? ? - see Digoxin toxicity
Contraindications - intermittent complete heart block or second degree atrioventricular block, especially if there is a history of Stokes-Adams attacks.

- arrhythmias caused by cardiac glycoside intoxication.

- supraventricular arrhythmias associated with an accessory atrioventricular pathway, as in the Wolff-Parkinson-White syndrome, unless the electrophysiological characteristics of the accessory pathway and any possible deleterious effect of digoxin on these characteristics have been evaluated. If an accessory pathway is known or suspected to be present and there is no history of previous supraventricular arrhythmias, digoxin is similarly contraindicated.

- ventricular tachycardia or ventricular fibrillation.

- hypertrophic obstructive cardiomyopathy

Mechanism

  • inhibits Na+/K+ ATPase (an antiporter)
  • so ↑ intracellular Na
  • ↑ intracellular Na → ↑Ca influx

Effects

positive inotropy
↑ vagal tone → ↓ conduction through AV node
↓ duration of Phase 2

Contraindications

  • Supraventricular arrhythmias associated with accessory pathways (such as Wolff-Parkinson-White syndrome).
  • Intermittent complete heart block; second-degree atrioventricular (AV) block.
  • Myocarditis
  • Ventricular tachycardia or ventricular fibrillation.

#pharmacology #cardiac-physiology

Effect of digoxin on cardiac AP
Digoxin toxicity

https://derangedphysiology.com/main/cicm-primary-exam/required-reading/cardiovascular-system/Chapter%20968/digoxin love u
SPC page actually very helpful