High Risk Drugs

Question 1

What is digoxin?

Answer 1

A cardiac glycoside that is
positively ionotropic; and
negatively chronotropic

Question 2

What is digoxin indicated for? (3)

Answer 2

Atrial fibrillation
Atrial flutter
Heart failure

Question 3

How frequently is digoxin given?

Answer 3

OD, but can be BD in higher doses to reduce risk of nausea

Question 4

What is the half life of digoxin?

Answer 4

30 - 40 hours

Question 5

What risk is associated with giving digoxin to a hypokalaemic patient? How is the risk minimised?

Answer 5

Higher risk of toxicity; given with a K+ sparing diuretic e.g. amiloride (NOT spironolactone)

Question 6

How is digoxin toxicity treated?

Answer 6

Administration of digoxin specific antibodies

Question 7

What is the therapeutic range for serum digoxin concentration?

Answer 7

0.7 - 2 mcg/L

Question 8

Toxicity is more likely to occur when serum levels of digoxin are above _____.

Answer 8

3.0 mcg/L

Question 9

What electrolyte imbalances are cautioned in use of digoxin? (4)

Answer 9

Hypercalcaemia

Hypokalaemia
Hypomagnesaemia
Hypoxia

Question 10

What should be monitored in patients taking digoxin? (3) How often?

Answer 10

U&Es, renal function and heart rate

every year at least

Question 11

What are some side effects of digoxin? (4)

Answer 11

Blurred/yellow vision
CNS effects e.g. confusion, dizziness
GI disturbances
Heart block

Question 12

What drugs can DECREASE the plasma concentration of digoxin?

Answer 12

St John’s Wort

Rifampicin

Question 13

What drugs can INCREASE the plasma concentration of digoxin?

Answer 13

Spironolactone
Quinines
Rate-limiting CCBs
Amiodarone
Macrolides

Question 14

Concomitant use of which drugs should be considered before prescribing digoxin? (2)

Answer 14

Drugs that cause hypokalaemia e.g. loop diuretics

Nephrotoxic drugs e.g. NSAIDs, ACEis

Question 15

What is amiodarone?

Answer 15

A class III antiarrhythmic (K+ channel blocker), used when first-line treatment is contraindicated/inappropriate

Question 16

How is amiodarone dosed?

Answer 16

200 mg TDS for the first week, then
200 mg BD for the nest week, then
200 mg OD as maintenance

Question 17

What is the half-life of amiodarone?

Answer 17

≈ 50 days

Question 18

What are some side effects of amiodarone? (5)

Answer 18

Corneal microdeposits
Thyroid dysfunction
Hepatotoxicity
Pulmonary toxicity
Photosensitivity
Sleep disorders
Altered taste

Question 19

What should patients on amiodarone be made aware of? (3)

Answer 19

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

Question 20

What does amiodarone to CYP450 enzymes?

Answer 20

Inhibits them - can cause an increase of plasma conc. for other drugs

Question 21

How should the dose of warfarin change if given with amiodarone? What monitoring should be done?

Answer 21

Reduce dose by ⅓ - ⅔ and monitor INR

Question 22

How should the dose of digoxin change if given with amiodarone? What monitoring should be done?

Answer 22

Half the dose and monitor for toxicity

Question 23

How do beta blockers and amiodarone interact?

Answer 23

Can increase the risk of CV events e.g. AV block, MC depression, bradycardia