Cardiac glycosides

Question 1

digoxin pharmacokinetics

Answer 1

large Vd so in myocardium
long half life
renal elimination
low protein binding

Question 2

antibiotic effects on digoxin

Answer 2

digoxin is metabolized by gut microflora so absorption can be altered by antibiotics
increased in potential toxicity

Question 3

cardiac effects of dig

Answer 3

increased inotropy 
increased automaticity 
decreased rate of conduction 
shortened repolarization intervals
QT shortened 
scooping of the ST segment

Question 4

dig effects on autonomic nervous system

Answer 4

parasym = increased release of acetylcholine 
sym = increased efferent sympathetic discharge

Question 5

digoxin toxic dose

Answer 5

1mg in a child
3mg in an adult
>10mg in healthy subject = cardiac arrest
>3mg in child = cardiac arrest

Question 6

digoxin toxic levels

Answer 6

> 2ng/mL

Question 7

drug interactions

Answer 7

amiodarone (inhibits tubular secretion)
antibiotics
quinidine
verapamil

Question 8

risk factors for toxicity

Answer 8

drug interactons
renal failure
MI
electrolyte imbalance
elderly

Question 9

symptoms and signs of acute overdose

Answer 9

vomit
hyperkalemia
sinus bradycardia
sinoatrial arrest
second or third degree av block 
ventricular tachycardia/fibrillation 
intracellular myocardial hypercalcemia

Question 10

symptoms and signs of chronic toxicity

Answer 10

visual disturbance - dychromatopsia
weakness
sinus bradycardia
afib
ventricular arrhythmia 
junctional tachycardia
paroxymal atrial tachycardia 
hypokalemia and hypomagnesemia from the use of diuretics

Question 11

supportive measures for dig

Answer 11

protect airways, assist ventilation
treat hyperkalemia - insulin and glucose
bradycardia or heart block - atropine
treat ventricular tachyarrhythmias - lidocaine

Question 12

management of intoxicated patient

Answer 12

gastric emptying
activated charcoal
MDAC
digoxin specific antibody fragments

Question 13

monitoring of digoxin levels

Answer 13

monitor before giving antibodies bc thats what makes you decide you need to use them
dont monitor levels bc they will be increased due to presence of complexes redistributes drug from heart into plasma

Question 14

when do you use digoxin specific antibody fragments

Answer 14

toxicity related to digoxin, digitoxin, natural cardiac glycosides

Question 15

how does digifab work

Answer 15

bind to intravascular free digoxin

affinity for digifab greater than the affinity for the atpase

Question 16

admin of digifab

Answer 16

infusion over 15min to 2hr

Question 17

time response for digifab

Answer 17

onset 19min

complete response 88min

Question 18

dose of digibind

Answer 18

vial = .5mg of digoxin 
# of vials = dig serum conc x wt /100
# of vials = amount ingested/.5

Question 19

empiric dosing acute ingestion

Answer 19

adult : 10-20 vial

child: 10-20 vial

Question 20

empiric dosing chronic ingestion

Answer 20

adult: 3-6 vial
child: 1-2 vial

Question 21

use digoxin specific antibody fragments for

Answer 21

life threatening cardiac glycosides toxicity
porgressive bradydysrhythmias
severe ventricular dyshrhythmia
potassium >5.5
acute ingestion >10mg adult, >4mg child
serum levels >10ng/mL
rapid progression of clinical signs and symptoms and rising potassium levels

Question 22

metabolic acidosis in cardioglycosides?

Answer 22

no

Question 23

labs to ask for

Answer 23

electrolytes
bicarb
creatinine
glucose
BUN
CPK
LDH
serum digoxin