digoxin Flashcards
when are digoxin specific antibody fragments indicated
reversal of life-threatening overdosage.
serious cases of digoxin toxicity should be discussed with
national poisons information service
serious manifestations need urgent specialist referral
MOA
cardiac glycoside that increases the force of myocardial contraction and reduces conductivity within the atrioventricular (AV) node.
half the dose of digoxin if taken with the following 3 drugs
amiodarone
dronedarone
quinine
when switching from IV to oral, may need to increase dose by … to maintain same plasma-digoxin conc
20-33%
the following 3 electrolytes have risk of digitalis toxicity
hypercalcaemia
hypokalaemia
hypomagnesaemia
the following event has risk of digitalis toxicity
hypoxia
interaction with amino/theophylline
they are predicted to increase risk digoxin toxicity
caution
interaction with amiodarone
it moderately increases exposure to digoxin. halve digoxin dose and monitor
increased risk of bradycardia
these vitamin drugs interact with digoxin
vitamin D preps - e.g. calcitriol, alfacalcidiol, colecalciferol
they increase risk of toxicity! monitor!
remember - hypercalcaemia predisposes toxicity
this class of drugs commonly used as immunotherapy interacts
CCs increase risk of digoxin toxicity
caution
how to treat known or strongly suspected life threatening digoxin toxicity associated with ventricular arrhythmias or bradyarrhytmias
gie atropine
if unresponsive, digoxin specific antibody fragments can be given
these can also be given when measured beyond withdrawal of digoxin and correction of any electrolyte abnormalities are considered necessary
discuss its use in AF
controls ventricular response in persistent and permanent AF and atrial flutter
For management of atrial fibrillation the maintenance dose of digoxin can usually be determined by….
ventricular rate at rest, which should not usually be allowed to fall persistently below 60 beats per minute.
ventricular rate at rest should not usually be allowed to fall persistently below
60bpm
is a loading dose required in pt with HF
no
a satisfactory plasma-digoxin concentration can be achieved over a period of about a week.
…. function is the most important determinant of digoxin dosage
renal
Digoxin has a long half-life and maintenance doses need to be given only once daily although higher doses may be divided to avoid this side effect
nausea
The plasma concentration alone cannot indicate toxicity reliably, but the likelihood of toxicity increases progressively through the range
1.5-3 micrograms/litre
why should it be used with care in elderly
susceptible to digalitis toxicity
Hypokalaemia predisposes the patient to digitalis toxicity; it is managed by ….
giving a potassium-sparing diuretic or, if necessary, potassium supplementation.
what to do if toxicity occurs but no serious manifestations
withdraw digoxin
correct any electrolyte disturbances
unwanted effects depend on (2)
concentration of digoxin in the plasma
sensitivity of the conducting system or of the myocardium, which is often increased in heart disease
why are CCs, B2 agonists, theophylline, loop and thiazides etc predicted to increase risk of toxicity?
hypokalaemia
this abx class is predicted to increase the conc of digoxin. monitor digoxin conc
macrolides - clarith, erythromycin, azith
these antifungals interaction
amphotericin B - predicted to increase the risk of Digoxin toxicity when given with Digoxin. Manufacturer advises caution.
Azoles - itracon, ketocon, posacon,
are predicted to markedly increase the concentration of Digoxin. Manufacturer advises monitor Digoxin concentration.
St Johns wart interaction
St John’s wort decreases the concentration of Digoxin. Manufacturer advises avoid.
RL-CCB interaction
Verapamil, diltiazem increases the concentration of Digoxin. Manufacturer advises monitor and adjust dose.
Both Digoxin and Verapamil can increase the risk of bradycardia.
interaction with acetylcholinesterase inhibitors, BB (no class of interaction)
e.g. rivastigmine, donepezil, galantamine
increase risk of bradycardia
spinorolactone, eplerenone interaction
Spironolactone increases the concentration of Digoxin. Manufacturer advises monitor and adjust dose.
IV calcium interaction
intravenous Calcium increases the effects of Digoxin. Manufacturer advises avoid.
quinine, chloroquinine, mefloquine interaction
Quinine increases the concentration of Digoxin. Manufacturer advises monitor and adjust Digoxin dose.
Mefloquine is predicted to increase the risk of bradycardia when given with Digoxin. Manufacturer makes no recommendation.
anti arrhythmic interactions - propafenone, dronedarone,
Dronedarone is predicted to moderately increase the exposure to Digoxin. Manufacturer advises monitor and adjust Digoxin dose.
routine monitoring not needed. however, when you do take plasma-digoxin conc assay when should blood be taken after dose?
For plasma-digoxin concentration assay, blood should be taken at least 6 hours after a dose.
monitoring
Monitor serum electrolytes and renal function. Toxicity increased by electrolyte disturbances.
common SE
Arrhythmias; cardiac conduction disorder; cerebral impairment; diarrhoea; dizziness; eosinophilia; nausea; skin reactions; vision disorders; vomiting
What are some symptoms of toxicity
GI disturbances: nausea, vomiting, diarrhoea
Visual disturbances: blurred vision, yellow vision, halos around lights
Neurological disturbances: confusion, dizziness, fatigue
Cardiac: bradycardia, arrhythmias, heart block
What to do if digoxin toxicity suspected
If toxicity is suspected, check digoxin levels and electrolytes, adjust dosage, may need to withdraw digoxin and correct any electrolyte imbalances and, in severe cases, treat with digoxin-specific antibodies (Digibind).
