6 - Cardiac Medications Flashcards
Which drug follows the one CM when given IV?
Caffeine
What is the equation for Ro in the 1 CM?
Ro = Cl * Css
What is digoxin and what are its indications?
- Cardiac glycoside
- Inotroph for congestive heart failure and rate control for A fib
At what F(u) is the value considered irrelevant and the drug wouldn’t require dosing changes for renal dysfunction?
F(u) under 30%
Difference between Fe and Fu
- Fe = free fraction (Fe = 70% means 30% is protein bound)
- Fu = fraction excreted unchanged renally
Describe atrial fibrillation
- 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
Can a pt get a pulmonary embolism from A fib?
No
What is the formula of Dobb’s?
Css (mcg/L) = [F * dose in mcg/day] / [CrCl * 1.2 + 31]
Bioavailability of digoxin
Oral is 75% of IV
What are some typical digoxin toxicity sx?
Nausea and abdominal cramping
What is an easy way to determine a new regimen for a pt experiencing toxicity of a drug?
Ro (old regimen) / Css (old) = Ro (new) / Css (new)
How can you calculate dose?
Css * Vd * S * F
- S = salt
What are some special considerations with digoxin since it is a 2-compartment drug?
- 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)
What are the recommended digoxin maintenance doses based on ClCr?
- 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
Formula for Css peak
[S * F * dose] / [Vd * 1-e^-ke*tao]
What do class 3 and 4 of the NYHA classification represent for heart failure?
- Class 3 = mild exertion to have sx
- Class 4 = no exertion to have sx
Should digoxin be monitored to be in a certain range?
- No evidence that elevated levels cause HF and increased mortality
- HF causes elevated digoxin levels b/c kidneys aren’t working properly
Which drugs are in class 2 and class 4 of the Vaughn-Williams classification of antiarrhythmic agents? Which class are amiodarone and digoxin in?
- Class 2 = beta blockers
- Class 4 = non-DHP CCBs (verapamil, diltiazem)
- Amiodarone = class 3
- Digoxin = class 5
Indications of amiodarone
- Tx of ventricular tachycardia/fibrillation
- Conversion to normal sinus rhythm from atrial flutter or fibrillation
- Rate control for atrial fibrillation
Bioavailability of amiodarone
50%
What is significant about the structure of amiodarone?
Has an iodine group, which gives anti-arrhythmic effect but also gives toxicity
What are some adverse effects of amiodarone?
- Dizziness, fatigue, tremor
- Pneumonitis (can be life-threatening)
- Hypotension, bradycardia w/ IV, QT prolongation
- N/V
- Corneal microdeposits
- Slate blue discolouration of skin
Loading dose of amiodarone for atrial arrhythmias?
600-800 mg/day (usually in divided doses) for a total of 10 g
Maintenance dose of amiodarone for atrial arrhythmias?
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
Example of loading dose for amiodarone for atrial arrhythmias
- 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
Loading dose of amiodarone for ventricular arrhythmias?
400-1200 mg/day (usually in divided dose) for total of 8-10 g
Maintenance dose of amiodarone for ventricular arrhythmias?
200-400 mg/day w/ lower doses carrying less risk of adverse effects
Example of loading dose for amiodarone for ventricular arrhythmias
- 400 mg TID for 5 days (6 g)
- 400 mg BID for 5 days (4 g)
- Total of 10 g achieved over 10 days
