Outline the differences between heparin and enoxaparin with respect to:
· Monitoring of effect
· Adverse effects
· Reversal of effect
Candidates were expected to mention the differences between heparin and enoxaparin and to
explain why these differences existed and their implications.
heparin Pharmacokinetics -
MW3000-30000. Large variability has significant effects on:
· mechanism of action (IIa, IXa, Xa)
· dosing( 2/3 molecules in dose have no active binding sites)
· bioavailability poor,T1/2 short (rapid uptake by PF4/endo cells/macrophages and
proteins of high MW components) = poor predictability and dose response both IV and
SC, mandates monitoring IV
T1/2 1-2 hours: S/C 2-3 daily doses. Continuous IV – advantage is fast offset.
MW3000-5000. Inhibits Xa only.
· bioavailability (100%),longer T1/2 no uptake/protein binding
· predictable activity and dose response = decreased need for monitoring, reliable SC
· No need for IV use
T1/2 4-5 hours, 1-2 daily dosing, but no fast offset.
Better answers were in tabular format under each heading. Higher marks were awarded for
mentioning of monitoring pitfalls such as heparin resistance, measuring Xa levels in a timely
fashion, and the efficacy and pitfalls of protamine with each agent.
Syallabus J2 2a
Reference: Stoelting 505-511