Digoxin

Question 1

Digoxin is indicated in?- what are its usual doses and what is its moA? Af AND hf???

Answer 1

Indications and Dose
➢ AF or flutter (125 – 250 mcg) ➢ HF (62.5 – 125 mcg)
Mechanism of Action
Cardiac glycoside that increases the force of myocardial contraction and reduces conductivity within the atrioventricular (AV) node.

Question 2

Common side effects DIGOXIN yellooowwwww!!!!- 8

Answer 2

➢ Arrhythmias
➢ Cardiac conduction disorder
➢ Cerebral impairment
➢ Diarrhoea
➢ Dizziness
➢ Skin reactions
➢ Vision disorders
(yellow vision)
➢ Nausea and vomiting

Question 3

Digoxin Contra-indications(WPWS, THink all heart)

Answer 3

➢ Supraventricular arrhythmias associated with accessory conducting pathways e.g. Wolff-Parkinson-White syndrome
➢ Ventricular tachycardia or fibrillation
➢ Intermittent complete heart block
➢ Myocarditis

Question 4

Elderly (Prescription potentially inappropriate) digoxin- there’s no clear what seen?? What is their renal function and dose and so what could that do ?

Answer 4

STOPP criteria
➢ In heart failure with normal systolic ventricular function (no clear evidence of benefit)
➢ at a long-term dose greater than 125 micrograms daily if eGFR less than 30 mL/minute/1.73 m2 (risk of digoxin toxicity if plasma levels not measured)

Question 5

Digoxin - Therapeutic Range and Toxicity- how often do you measure? And what do you mentor and why?and it has a long half life thus…. How many doses would we expect?? What can it be hard to distinguish? What by do we withdraw?

Answer 5

➢ 0.8-2 mcg/L (toxicity - above 1.5mcg/L) - measure 6hrs after dose
➢ Monitor electrolytes & renal function (renally eliminated)
➢ Long half-life thus daily dose
➢ Can be difficult to distinguish between toxic effects and clinical deterioration as symptoms are similar
➢ Withdraw digoxin if toxicity or <60 bpm

Question 6

Cautions digoxin- other name for digoxin is digitalis!!!!! Toxicity increases with which electrolyte imbalances???what is hypoxia? What else what other conditions - (remember digoxin the dentist)

Answer 6

Cautions
➢ Risk of digitalis toxicity increases with
HYPERcalcaemia, HYPOkalaemia, hypoxia and HYPOmagnesaemia.
➢ Recent myocardial infarction
➢ Severe respiratory disease
➢ Thyroid disease

Question 7

Bioavailability- digoxin- switching from iIV to oral?

Answer 7

➢ IV – 100%
➢ Tablet – 90%
➢ Elixir – 75%
➢ Switching from IV to
oral route may need to increase dose by 20–33% to maintain the same plasma- digoxin concentration

Question 8

Digoxin interactions- which would we have to reduce the dose for by half? Which drugs increase plasma concentration via impairing renal function? Which increase plasma conc via hypokalaemia? Which reduce conc? Which increase conc?

Answer 8

Interactions
Reduce dose by half with concurrent use
*Amiodarone, dronedarone and quinine
Drugs that increase plasma concentration via impairing renal function
*Diuretics, NSAIDs and ACE inhibitors
Drugs that increase plasma concentration via hypokalaemia
*Loop and thiazide diuretics, B2 agonists, theophylline and steroids
Drugs that reduce plasma concentration
*St. Johns Wort and Rifampicin
Drugs that increase plasma concentration
*Amiodarone, diltiazem, verapamil, macrolides, mirabegron, itraconazole and ciclosporin

Question 9

Amiodarone

Answer 9

• can cause corneal micro deposits - driving
• thyroid
  Photosensitivity
  Bradycardia a
  Pilomary toxicty
  Qt prolongation
  Gyp450 inhibitor so increases level of other drugs
  Digoxin - need to half the dose

Monitor TSH, LFT,Vit K, chest X-ray
Eye exa,
If IV- monitor ecg and liver transamisterase