Warfarin

Question 0

Peak effect

Answer 0

72-96hrs

Question 1

Absorption

Answer 1

Completely absorbed on the upper GI tract

Question 2

Duration of action

Answer 2

2 to 5 days

Question 3

Distribution

Answer 3

Low volume of distribution

Highly protein bound 99.5%

Question 4

Metabolised

Answer 4

Almost entirely metabolised by inactive metabolites by hepatic microsomal enzyme CYP450

Question 5

Excretion

Answer 5

Urine secretion in the form of metabolites. Very little is secreted uncharged

Question 6

Slow onset of action

Answer 6

Result of indirect mechanism of action.

Onset - takes several days. Doesn’t directly inhibit factors so takes days for the functioning factors to be cleared from the circulation, before full effect.

Question 7

Slow offset of action

Answer 7

Body takes several days to produce new, functional clotting factors when warfarin therapy is stopped.
Problem of patients experience trauma or require emergency surgery.

Question 8

An anticoagulant effect is generally achieved in …days ?

Answer 8

4 to 7 days

Question 9

Drug-drug interaction

Answer 9

Associated with high d-d interaction
Highly protein bound = if another high protein bound drug is given that drug could displace warfarin = increase anticoagulant effect = increase bleeding.
Metabolised by CY P450

Question 10

Drug food interaction

Answer 10

Foods rich in vitamin K can reduce the anticoagulant effect of warfarin.
Alcohol intake - interfere with metabolic pathways and can cause increase bleeding risk.

Question 11

Narrow therapeutic window

Answer 11

Morrow window in which W provides effective stroke prevention.
Measured through INR - measures bloods ability to coagulate.
TR = 2-3.
3 = increase risk of intercranial bleeding