High Risk Drugs Flashcards
What is digoxin?
A cardiac glycoside that is
positively ionotropic; and
negatively chronotropic
What is digoxin indicated for? (3)
Atrial fibrillation
Atrial flutter
Heart failure
How frequently is digoxin given?
OD, but can be BD in higher doses to reduce risk of nausea
What is the half life of digoxin?
30 - 40 hours
What risk is associated with giving digoxin to a hypokalaemic patient? How is the risk minimised?
Higher risk of toxicity; given with a K+ sparing diuretic e.g. amiloride (NOT spironolactone)
How is digoxin toxicity treated?
Administration of digoxin specific antibodies
What is the therapeutic range for serum digoxin concentration?
0.7 - 2 mcg/L
Toxicity is more likely to occur when serum levels of digoxin are above _____.
3.0 mcg/L
What electrolyte imbalances are cautioned in use of digoxin? (4)
Hypercalcaemia
Hypokalaemia
Hypomagnesaemia
Hypoxia
What should be monitored in patients taking digoxin? (3) How often?
U&Es, renal function and heart rate
every year at least
What are some side effects of digoxin? (4)
Blurred/yellow vision
CNS effects e.g. confusion, dizziness
GI disturbances
Heart block
What drugs can DECREASE the plasma concentration of digoxin?
St John’s Wort
Rifampicin
What drugs can INCREASE the plasma concentration of digoxin?
Spironolactone Quinines Rate-limiting CCBs Amiodarone Macrolides
Concomitant use of which drugs should be considered before prescribing digoxin? (2)
Drugs that cause hypokalaemia e.g. loop diuretics
Nephrotoxic drugs e.g. NSAIDs, ACEis
What is amiodarone?
A class III antiarrhythmic (K+ channel blocker), used when first-line treatment is contraindicated/inappropriate
How is amiodarone dosed?
200 mg TDS for the first week, then
200 mg BD for the nest week, then
200 mg OD as maintenance
What is the half-life of amiodarone?
≈ 50 days
What are some side effects of amiodarone? (5)
Corneal microdeposits Thyroid dysfunction Hepatotoxicity Pulmonary toxicity Photosensitivity Sleep disorders Altered taste
What should patients on amiodarone be made aware of? (3)
Phototoxicity - shield skin and use wide-spec sunscreen
Pulmonary toxicity - look out for SOB/cough
Hepatotoxicity - signs of liver damage e.g. jaundice, dark urine
What does amiodarone to CYP450 enzymes?
Inhibits them - can cause an increase of plasma conc. for other drugs
How should the dose of warfarin change if given with amiodarone? What monitoring should be done?
Reduce dose by ⅓ - ⅔ and monitor INR
How should the dose of digoxin change if given with amiodarone? What monitoring should be done?
Half the dose and monitor for toxicity
How do beta blockers and amiodarone interact?
Can increase the risk of CV events e.g. AV block, MC depression, bradycardia
