6 - Cardiac Medications

Question 1

Which drug follows the one CM when given IV?

Answer 1

Caffeine

Question 2

What is the equation for Ro in the 1 CM?

Answer 2

Ro = Cl * Css

Question 3

What is digoxin and what are its indications?

Answer 3

• Cardiac glycoside

- Inotroph for congestive heart failure and rate control for A fib

Question 4

At what F(u) is the value considered irrelevant and the drug wouldn’t require dosing changes for renal dysfunction?

Answer 4

F(u) under 30%

Question 5

Difference between Fe and Fu

Answer 5

• Fe = free fraction (Fe = 70% means 30% is protein bound)

- Fu = fraction excreted unchanged renally

Question 6

Describe atrial fibrillation

Answer 6

• Chaotic looking baseline
• Irregular heart rate
• Ventricles are undergoing contraction (obvious by QRS) but atria are quivering (obvious by P and T baseline), so not properly filling ventricles

Question 7

Can a pt get a pulmonary embolism from A fib?

Answer 7

No

Question 8

What is the formula of Dobb’s?

Answer 8

Css (mcg/L) = [F * dose in mcg/day] / [CrCl * 1.2 + 31]

Question 9

Bioavailability of digoxin

Answer 9

Oral is 75% of IV

Question 10

What are some typical digoxin toxicity sx?

Answer 10

Nausea and abdominal cramping

Question 11

What is an easy way to determine a new regimen for a pt experiencing toxicity of a drug?

Answer 11

Ro (old regimen) / Css (old) = Ro (new) / Css (new)

Question 12

How can you calculate dose?

Answer 12

Css * Vd * S * F

- S = salt

Question 13

What are some special considerations with digoxin since it is a 2-compartment drug?

Answer 13

• Myocardium senses the drug w/in the 2nd compartment
• Transiently high concentrations are achieved after every dose, however they don’t result in an immediate cardiac effect
• Draw levels just prior to next dose (trough) or at least 6 hours after dose was given (either IV or PO)

Question 14

What are the recommended digoxin maintenance doses based on ClCr?

Answer 14

• Clcr 50-100 = 250 mcg once daily IV or PO
• Clcr 10-50 = 125 mcg once daily IV or PO
• Clcr < 10 = 62.5 mcg once daily IV or PO

Question 15

Formula for Css peak

Answer 15

[S * F * dose] / [Vd * 1-e^-ke*tao]

Question 16

What do class 3 and 4 of the NYHA classification represent for heart failure?

Answer 16

• Class 3 = mild exertion to have sx

- Class 4 = no exertion to have sx

Question 17

Should digoxin be monitored to be in a certain range?

Answer 17

• No evidence that elevated levels cause HF and increased mortality
• HF causes elevated digoxin levels b/c kidneys aren’t working properly

Question 18

Which drugs are in class 2 and class 4 of the Vaughn-Williams classification of antiarrhythmic agents? Which class are amiodarone and digoxin in?

Answer 18

• Class 2 = beta blockers
• Class 4 = non-DHP CCBs (verapamil, diltiazem)
• Amiodarone = class 3
• Digoxin = class 5

Question 19

Indications of amiodarone

Answer 19

• Tx of ventricular tachycardia/fibrillation
• Conversion to normal sinus rhythm from atrial flutter or fibrillation
• Rate control for atrial fibrillation

Question 20

Bioavailability of amiodarone

Answer 20

50%

Question 21

What is significant about the structure of amiodarone?

Answer 21

Has an iodine group, which gives anti-arrhythmic effect but also gives toxicity

Question 22

What are some adverse effects of amiodarone?

Answer 22

• Dizziness, fatigue, tremor
• Pneumonitis (can be life-threatening)
• Hypotension, bradycardia w/ IV, QT prolongation
• N/V
• Corneal microdeposits
• Slate blue discolouration of skin

Question 23

Loading dose of amiodarone for atrial arrhythmias?

Answer 23

600-800 mg/day (usually in divided doses) for a total of 10 g

Question 24

Maintenance dose of amiodarone for atrial arrhythmias?

Answer 24

200-300 mg/day

- Go w/ 300 if pt having sx of A. fib during titration of loading dose; try 300 for 1 month then go to 200

Question 25

Example of loading dose for amiodarone for atrial arrhythmias

Answer 25

• 200 mg TID for 14 days (8.4 g)
• 200 mg BID for 4 days (1.6 g)
• Total of 10 grams achieved over 18 days

Question 26

Loading dose of amiodarone for ventricular arrhythmias?

Answer 26

400-1200 mg/day (usually in divided dose) for total of 8-10 g

Question 27

Maintenance dose of amiodarone for ventricular arrhythmias?

Answer 27

200-400 mg/day w/ lower doses carrying less risk of adverse effects

Question 28

Example of loading dose for amiodarone for ventricular arrhythmias

Answer 28

• 400 mg TID for 5 days (6 g)
• 400 mg BID for 5 days (4 g)
• Total of 10 g achieved over 10 days