This document provides information on anticoagulant therapy and laboratory monitoring. It discusses the goals and indications for anticoagulant therapy including preventing thrombosis. It describes the traditional approach using heparin, coumarins, and antiplatelet drugs. Assays for monitoring anticoagulant therapy include global screening assays like PT, aPTT, and TT as well as more specific chromogenic assays. The mechanisms and monitoring of oral anticoagulants like warfarin are explained in detail. Warfarin inhibits vitamin K and factors II, VII, IX and X. Polymorphisms affecting warfarin metabolism and response are also covered. The mechanisms and uses of unfractionated and low molecular weight hepar

1. Lecture
9
Laboratory
Monitoring
of
An3coagulant
Therapy
Assays
to
Monitor
An3coagulant
Response
to
Therapy

2. An3coagulant
Therapy
• Goal
▫ Prevent
the
forma-on
or
extension
of
a
thrombus
• Indica3ons
▫ Arterial
thrombosis
▫ Atrial
fibrilla3on
▫ Cerebrovascular
disease
▫ Extracorporeal
procedures
–
Renal
dialysis,
CPB
▫ Mechanical
heart
valves
▫ Myocardial
infarc3on
▫ Peripheral
vascular
disease
▫ Radiologic
procedures
–
Interven3onal/Diagnos3c
▫ Venous
thromboembolism
–
DVT/PE
2

4. Tradi3onal
Approach
to
An3coagulant
Therapy
4
Heparin
Coumarins
Clot
busters
Aspirin
Venous
thrombosis
Arterial
thrombosis
Clot
lysis
Target
thrombin
genera3on
Interfere
platelet
func3on

5. Two
Classes
of
An3coagulant
Drugs
• An3coagulant
Drugs
– Inhibit
in
vivo
thrombosis
– Prolong
cloMng
3me
– Show
concentra3on-­‐
dependent
effect
on
the
clot-­‐based
assays
– Monitored
with
tradi-onal
assays
• An3thrombo3c
Drugs
– Inhibit
in
vivo
thrombosis
– “Variable”
prolonga3on
of
the
cloMng
3me
– Monitored
with
nontradi-onal
assays
for
monitoring
effec3vely
5

6. Clot-­‐based
Assays
Global
screening
assays
Chromogenic
Assays
• Nonspecific
– PT,
aPTT,
TT,
ACT
– Depend
on
a
func-onal
coagula3on
cascade
– Phospholipid
dependent
– Subject
to
numerous
preanaly-cal
variables
• Coagula3on
factor
abnormali3es
• Inhibitors
• Concurrent
drug
interac3ons
– Fast
and
inexpensive
– PT,
aPTT,
TT,
ACT
• Protein
converted
to
its
ac3ve
form
• Enzyme
cleaves
(hydrolyzes)
a
substrate
– Consists
of
a
pep3de
sequence
and
a
chromophore
(pNA)
• Pep3de
releases
the
pNA
à
gives
off
a
color
• Measure
intensity
of
the
color
• Subject
to
fewer
preanaly3cal
variables
6
Ca2+
+
Reagent
Pa3ent
Plasma
Bates S M , Weitz J I Circulation
2005;112:e53-e60

7. Oral
An3coagulants
• Most
common
of
the
oral
an3coagulants
• Frank
W
Schofield,
1922
▫ Reported
a
bleeding
diathesis
in
ca^le
that
simulated
hemorrhagic
sep3cemia
and
“black
leg
syndrome”
▫ Spoiled
sweet
clover
mixed
with
hay
7

8. Oral
An3coagulants
• Karl
Paul
Link,
1933,
University
of
Wisconsin
– A
WI
farmer—pail
of
blood
that
would
not
coagulate
– Isolated
and
purified
3,3’-­‐methylene-­‐bis-­‐[4-­‐hydroxycoumarin]
– Dicumarol
and
WARF-­‐42
• Led
to
the
iden3fica3on
of
Coumarin
(Warfarin)
8

9. Oral
An3coagulants
• Called
Warfarin—WI
Alumni
Research
Founda3on,
1948
• Mechanism
à
greatly
diminished
prothrombin
ac3vity
and
delayed
the
blood
cloMng
mechanism
▫ Ini-ally
used
as
a
roden-cide
▫ Army
inductee
1951
▫ Dwight
D
Eisenhower
1955
9

10. Warfarin
• Coumarins—class
of
drugs
which
inhibit
vitamin
K
ac3vity
▫ Warfarin
(Coumadin)
▫ Acenocoumarol
(Sintrom)
▫ Phenprocoumon
(Marcoumar)
• Indica3ons
▫ Atrial
fibrilla3on
▫ Prosthe3c
heart
valves
▫ Thromboembolic
disease
▫ Hypercoagulable
states
▫ Depressed
cardiac
func3on
10

11. Warfarin
and
Vitamin
K
• Warfarin
is
an
analogue
of
vitamin
K
• Vitamin
K
-­‐
discovered
from
defects
in
blood
“koagula3on”
• Vitamin
K
synthesized
by
plants
and
bacteria
▫ Leafy
green
vegetables
and
intes3nal
flora
• Vitamin
K
-­‐
required
coenzyme
for
post
transla3on
modifica3on
reac3on
• γ-­‐carboxyla3on
of
glutamic
acid
residues
1. Adds
carboxyl
group
(COOH)
onto
Gla
residues
of
the
vitamin
K
dependent
proteins
2. Needed
for
Ca2+
binding
à
clot
forma3on
• Warfarin
inhibits
the
ac-on
of
vitamin
K
• Vitamin
K
administra-on
is
the
an-dote
for
warfarin
toxicity
11
Similari3es
of
Warfarin
to
Vitamin
K

12. Vitamin
K
-­‐
Carboxyglutamate
FII,
FV,
FVII,
FX,
PC,
PS
ACTIVE
FII,
FVII,
FIX,
FX,
PC,
PS
INACTIVE
reduced
oxidized

13. Warfarin
• Racemic
mixture
of
two
op3cally
ac3ve
enan3omers–
R
and
S
▫ S
enanAomer
is
more
potent
• “S”
metabolized
primarily
by
the
CYP2C9
of
cytochrome
p450
• ½-­‐life
~
29
hours
• Oral
administra3on
• Water
soluble
• Rapidly
absorbed
in
stomach
and
duodenum
• Binds
to
albumin
(~98%)
▫ Only
the
non-­‐bound
(FREE)
form
is
biologically
ac3ve
• Peak
an3coagulant
effect
occurs
36-­‐42
hours
aper
drug
administra3on
13

14. Warfarin’s
An3coagulant
Effect
— Does
NOT
have
a
DIRECT
an3coagulant
effect
— Onset
of
Warfarin’s
effect
is
dependent
on
the
½-­‐life
of
the
VKDFs
— PT/INR
elevates
rapidly
due
to
the
short
½-­‐life
of
FVII
• Full
onset
of
Warfarin’s
an3coagulant
effect
takes
from
72-­‐96
hours
— ***INR
does
NOT
become
stable
un-l
72-­‐96
hours
14
Factor
Decreased
aHer
iniAaAon
of
Warfarin
Factor
VII
6
hours
Factor
IX
24
hours
Factor
X
36
hours
Factor
II
72
hours

15. Ac3on
of
Warfarin
InacAve
FII,
FVII,
FIX,
FX,
PC,
PS
WARFARIN
INACTIVE
FII,
FV,
FVII,
FX,
PC,
PS

16. Polymorphism
CYP2C9
• CYP2C9*2
and
CYP2C9*3
• Reduce
clearance
of
S-­‐
enan3omer
• Increase
sensi3vity
to
warfarin
• Require
▫ Lower
dose
of
warfarin
▫ Longer
-me
to
reach
steady
state
▫ Result
– Higher
risk
for
over-­‐
an-coagula-on
and
serious
bleeding
– More
common
in
Caucasian
pa3ents
16
CYP2C9
CYP1A1
CYP1A2
CYP3A4
Warfarin
R-warfarin
R-warfarin
S-S-warfarin
Vitamin K
Reductase
Oxidized Vitamin K Reduced Vitamin K
O2
Hypofunctional
F. II, VII, IX, X
Protein C, S, Z
Functional
F. II, VII, IX, X
Proteins C, S, Z
CO2
Calumenin
γ-glutamyl
carboxylase

17. Polymorphism
of
VKORC1
Ø VKORC1
is
the
“target”
enzyme
for
Warfarin
Ø VKORC1
is
essen3al
cofactor
for
γ-­‐carboxyla3on
of
VKDFs
Ø Warfarin
inhibits
VKOR1’s
ac3vity
Ø Results
in
produc3on
of
“non-­‐
func3on”
PIVKAs
Ø VKORC1
polymorphisms
Ø Pa-ents
have
variable
resistance
and
sensi3vity
to
Warfarin
Ø Need
for
lower
doses
of
warfarin
during
long
term
therapy
17
Epoxide
Reductase
(VKORC1)
γ -Carboxylase
(GGCX)
Warfarin
Molecular
Interven-ons
6:223-­‐227,
(2006)

18. Heparin
• Probably
the
most
widely
prescribed
drug
in
the
US
• An3thrombo3c
proper3es
were
described
by
McLean
and
Howell
in
1918
• First
used
clinically
as
an
an3thrombo3c
agent
in
the
1930’s
• Heterogeneous
mixture
of
highly
sulfated
mucopolysaccharides
ranging
in
molecular
weight
from
3,000
–
30,000
Da
–>
averaging
15,000
Da
• Contains
alterna3ng
residues
of
D-­‐glucuronic
acid
and
N-­‐acetyl-­‐D-­‐
glucosamine
18

19. Heparin
• Naturally
occurring
an3coagulant
produced
by
basophils
and
mast
cells
• Exogenous
heparin
derived
from
two
sources
– Bovine
lung
3ssue
– Porcine
intes3nal
mucosa
• Two
forms
– Unfrac3onated
Heparin
(UFH)
– Low
Molecular
Weight
Heparin
(LMWH)
19

20. Heparin
• Used
clinically
to
treat
1. Prophylaxis
and
treatment
of
DVT
2. Treatment
of
PE
or
other
clinically
significant
thromboses
3. Acute
coronary
syndrome,
unstable
angina,
non-­‐ST
eleva3on
AMI
4. Preven3on
of
stroke
due
to
atrial
fibrilla3on
5. Intra-­‐opera3vely
• Cardiopulmonary
bypass
surgery
• Coronary
angioplasty
• Vascular
surgery
• Hemodialysis
• Administered
parentally
—(degraded
by
oral
administra3on)
20

21. Heparin:
Mechanism
of
Ac3on
• Mechanism
is
mediated
through
an3thrombin
in
the
coagula3on
cascade
• Exerts
is
an3coagulant
ac3vity
via
2
proteins
1. An3thrombin
(AT)
– Binds
to
an3thrombin
– Induces
a
conforma3on
change
in
AT
molecule
– Enhances
AT-­‐mediated
inhibi3on
of
– Thrombin,
Factor
Xa
– Factors
XIIa,
XIa,
IXa
2. Heparin
Cofactor
II
(HCII)
– Binds
to
heparin
cofactor
II
(HCII)
– HCII
requires
higher
levels
of
heparin
– Specifically
bind
to
thrombin

22. Unfrac3onated
Heparin
• In
the
absence
of
exogenous
heparin
▫ AT
binds
to
heparinoid
substances
located
on
the
endothelium
surface
– Dermatan
sulfate
– Chondroi3n
sulfate
– Heparan
sulfate
22
h^p://www.ncbi.nlm.nih.gov/pmc/ar3cles/PMC1915585/figure/Fig1/

23. Mechanism
of
Ac3on
UFH
• Polysaccharide
chain
–
18
saccharide
units
(nega3vely
charged)
• Binds
to
AT
(posi3vely
charged)
via
a
unique
pentasaccharide
sequence
• Induces
a
conforma-onal
change
in
the
AT
molecule
à
reac3ve
center
loop
of
AT
more
accessible
• Converts
AT
from
a
slow
progressive
inhibitor
to
an
aggressive
inhibitor
of
Thrombin
(IIa)
• Heparin
chains
are
released
and
used
again
23
NEJM,
337:688,
1997,
Weitz

24. Mechanism
of
Ac3on
UFH
• Polysaccharide
chain
containing
at
least
18
saccharide
units
• Binds
to
AT
via
a
unique
pentasaccharide
sequence
• Induces
a
conforma3onal
change
in
the
AT
molecule
• Converts
AT
from
a
slow
progressive
inhibitor
to
an
aggressive
inhibitor
of
thrombin
• Heparin
chain
then
serves
as
a
template
binding
AT
and
Thrombin—
(ternary
complex)
• Heparin
chain
is
released
and
is
used
again
• In
the
absence
of
exogenous
heparin
– AT
binds
to
heparinoid
substances
located
on
the
endothelium
surface
• Dermatan
sulfate
• Chondroi3n
sulfate
• Heparan
sulfate
24
NEJM,
337:688,
1997,
Weitz
Antithrombi
n
Thrombin
UFH
Pentasaccharide

25. Mechanism
of
Ac3on
for
LMWH
• Binds
to
AT
via
unique
pentasaccharide
sequence
• LMWH:AT
complex
binds
to
the
ac3ve
site
of
Xa
and
inhibits
its
ac3vity
• Exerts
its
an3coagulant
ac3vity
via
AT
• Mean
molecular
weight
5000
Daltons
– <
18
saccharide
units
— Advantages
— Bioavailability
approaches
100%
— Peak
an3-­‐Xa
ac3vity
occurs
between
3-­‐5
hours
sc
— Rarely
associated
with
HIT
— Does
not
cause
osteoporosis
— Usually
does
not
need
to
be
monitored
25
NEJM,
337:688,
1997,
Weitz

26. 1. FXa
Factor
Xa
Heparin
Assay
is
added
to
plasma
containing
syntheAc
factor
Xa
substrate
with
a
chromophore
a^ached
to
the
end
2. Substrate
is
cleaved
by
FXa
3. Chromophore
à
color
change
à
quan3fied
– Directly
propor3onal
to
enzyme
ac3vity
4. If
heparin
(UFH/LMW)
is
present
in
plasma
sample
à
it
will
promote
factor
Xa
inhibi3on
by
AT
à
less
FXa
available
to
cleave
substrate
5. Compared
to
standard
curve
using
known
amounts
of
heparin

27. Monitoring
UFH—aPTT
– Most
widely
used
test
– Adapted
to
monitor
heparin
therapy
– Inexpensive
and
easy
to
perform
• Perform
4-­‐6
hours
aper
bolus
dosage
and
every
24
hours
thereaper
– A
dose
adjustment
requires
monitoring
6
hours
aper
the
dose
adjustment
– 1.5-­‐2.5
x
“normal”
– Advantages
– Rapid
– Easy
to
perform
– Inexpensive
– Widely
available
27

28. Factors
Affec3ng
the
aPTT
Variable
Mechanism
Sample
collec3on
and
processing
Time
of
blood
sampling
Diurnal
varia3on
Citrate
concentra3on
>
Concentra3on
à
>
prolonga3on
Centrifuga3on
• Delayed
plasma
separa3on
(>1
hr)
à
shorter
cloMng
3me
à
PF4
• Platelet
count
<
10
x
109/L
Test
Characteris3cs
Reagent
Variable
responsiveness
to
UFH
Coagulometer
Differences
in
methods
of
end
point
detec3on
Biologic
variables
UFH
pharmacokine3cs
• Altered
intravascular
volume
(obesity,
aging)
• Increased
concentra3ons
of
heparin
binding
proteins
(infec3on,
inflamma3on,
malignancy)
aPTT
dose-­‐response
to
UFH
• Increased
FVIII
and
Fibrinogen
• Low
concentra3on
of
AT
(congenital,
acute
thrombosis,
LD)
• Reduced
levels
of
coagula3on
proteins
(DIC,
LD)
Baseline
aPTT
• LA
• Specific
factor
deficiencies
(PK,
HMWK,
XII,
XI,
IX,
VIII)
• Reduced
levels
of
coagula3on
proteins
(DIC,
LD)
28

29. Addi3onal
Tests
to
Monitor
UFH
• An3-­‐factor
Xa
assay
(UFH)
▫ 4
hours
aper
administra3on
▫ Therapeu3c
target—0.3-­‐0.7
anA-­‐Xa
U/mL
▫ Monitor
platelet
count
daily
▫ SUPERIOR
to
the
aPTT
assay
for
monitoring
UFH
therapy
29

30. Laboratory
Monitoring
of
LMWH
• Monitoring
not
required
in
most
pa3ents
• Collect
blood
sample
4
hours
aper
subcutaneous
dose
• Monitored
only
by
the
chromogenic
an3-­‐factor
Xa
assay
• Calibra3on
curve
– LMWH
that
the
pa3ent
is
on
– Commercial
calibrators
• Perform
regular
CBCs
to
monitor
platelet
count,
anemia,
occult
bloods
• Ranges:
– Target
range
for
prophylaxis—0.2
-­‐
0.4
an--­‐Xa
U/mL
– Therapeu-c
target
range
for
2x/day
dosing—0.5
-­‐
1.1
an--­‐Xa
U/mL
– Therapeu-c
target
range
for
1x/day
dosing—1.1
-­‐
2.0
an--­‐Xa
U/mL
• aPTT
can
not
be
used
to
monitor
LMWH
–
insensi-ve
to
LMWH
30

31. Heparins
h^p://quizlet.com/13750648/pharm-­‐test-­‐1-­‐
coagula3on-­‐flash-­‐cards/

32. Ac3vated
CloMng
Time
• Used
to
monitor
pa3ents
on
extremely
high
doses
of
heparin
– CPB
• Range
=
71
–
180
seconds
• Heparin
=
400
–
500
seconds
• Does
not
correlate
well
with
other
coagula-on
tests
32

33. Thrombin
Inhibitors
Thrombin
Inhibitors
Indirect
Thrombin
Inhibitors
Parenteral
UFH
LMWH
Fondaparinux
Oral
Rivaroxaban
Apixaban
Direct
Thrombin
Inhibitors
Parenteral
Hirudin
Lepirudin
Argatroban
Bivalirudin
Oral
Dabigatran
etexilate
33

34. Fondaparinux
(Arixtra)
— Synthe3c
pentasaccharide
— Mechanism
— Contains
the
unique
pentasaccharide
sequence
— Binds
to
AT
à
Inhibits
Factor
Xa
— Indirect
inhibitor
of
IIa
NEJM
34

35. Pharmacology
of
the
Pentasaccharides
• Predictable
dose
response
– Administered
1x/day
– Plasma
half-­‐life
14-­‐24
hours
– Does
not
bind
PF4
or
plasma
proteins
– Monitoring
generally
not
necessary
• Peak
ac3vity
–
3
hours
• No
an3dote,
protamine
ineffec3ve
– Most
common
adverse
reac3on
is
bleeding
– Excreted
by
the
kidneys
• Indica3ons
– Orthopedic
periopera3ve
DVT
prophylaxis
• Approved
for
use
in
the
preven3on
of
DVT
in
hip
and
knee
replacement
à
Fondaparinux
35
Pa-ents
with
history
of
HIT
Despite
no
reac-on
with
PF4*

36. Hirudin
• Most
powerful
naturally
occurring
inhibitor
of
thrombin
• Found
in
the
salivary
glands
of
medicinal
leech
(Hirudo
medicinalis)
• 65-­‐amino
acid
polypep-de
• Available
in
recombinant
form
– Lepirudin
and
Desirudin
– Differ
from
the
natural
form
only
by
the
absence
of
sulfated
tyrosine
residue
at
posi-on
-­‐63
• Plasma
half-­‐life—
60-­‐120
minutes
ader
subcutaneous
injec-on
• Excreted
by
the
kidneys
36
hp://www.theguardian.com/money/us-­‐money-­‐blog/2014/mar/09/
leech-­‐therapy-­‐brooklyn-­‐immigrants-­‐favor-­‐leeches

37. Lepirudin
(Refludan—Berlex)
• Recombinant
form
of
Hirudin
released
in
1988
• ~65
amino
acids
with
a
molecular
weight
of
7000
Daltons
• First
direct
thrombin
inhibitor
approved
by
FDA
for
HIT
• Pharmacology
– Inhibits
both
circula3ng
and
clot-­‐
bound
thrombin
– Does
not
cross-­‐react
with
HIT
an3bodies
– Plasma
half-­‐life—60-­‐120
minutes
– ~40%
of
pa-ents
develop
an-bodies
to
Lepirudin
• Prolongs
clearance
without
abroga3ng
its
ac3vity
▫ Monitoring
with
aPTT
▫ aPTT
target
is
1.5-­‐2.5
3mes
mean
reference
value
– 4
hrs
aper
ini3a3on
37

38. Argatroban
• Synthe33c
compe33ve
inhibitor
of
thrombin
derived
from
L-­‐
arginine
• Pharmacology
– Does
not
interact
with
PF4
– Smaller
size
makes
if
more
effec3ve
than
hirudin
at
inhibi3ng
clot-­‐bound
thrombin
– Metabolized
in
the
liver
and
excreted
in
the
feces
– Half-­‐life
~
45
minutes
38

39. Bivalirudin
(Angiomax)
• Synthe-c
20
amino-­‐acid-­‐
pep3de
analog
of
Hirudin
• ½-­‐life
~25
minutes
• Neutralizes
free
and
bound
thrombin
• No
an3body
forma3on
• Excreted
by
the
kidney
• Indica3ons
– Reduce
the
risk
of
acute
ischemic
complica-ons
a) Procedures
in
pa-ents
with
unstable
angina
pectoris
undergoing
PCI
b) Has
been
successful
in
pa-ents
with
HIT
39

40. New
“Oral”
An3coagulants
Direct
and
Indirect
Thrombin
Inhibitors
40

41. Dabigatran
Etexilate
Mesylate
(Pradaxa)
Boehringer-­‐Ingelheim
• Novel
oral
factor
IIa
inhibitor
• Cleared
by
FDA
(10/19/2010)
for
stroke
preven3on
in
atrial
fibrilla3on
• Prodrug
converted
to
an
ac3ve
drug
• Several
advantages
over
Warfarin
and
Enoxaparin
– Specifically
and
selec3vely
inhibits
both
free
and
clot
bound
thrombin
– Predictable
and
consistent
pharmacokine3c
profile
– Not
significantly
affected
by
interac3ons
with
food
– Not
metabolized
by
cytochrome
P450
system
• Does
not
affect
the
metabolism
of
other
drugs
that
u-lize
this
system
• Lower
poten-al
for
drug
interac-ons
41

42. Dabigatran
Pharmacology
• ½
life
14-­‐17
hours
• Bioavailability
~6-­‐7%
• Peak
plasma
levels
within
0.5-­‐2
hours
• Delayed
2
hours
by
food
• ~50%
of
the
drug
is
gone
12
hours
aper
a
dose
• Metabolized
by
the
liver
– No
liver
toxicity
– Dyspepsia
in
~11%
of
individuals
• Eliminated
mainly
via
the
kidneys
– GFR
<30
mL/min
~
28
hours
42

43. Rivaroxaban
(Xarelto)
Bayer/Johnson
&
Johnson
• Potent,
selec3ve,
oral
factor
Xa
inhibitor
• Cleared
by
FDA
(10/19/2012)
for
stroke
preven3on
in
atrial
fibrilla3on
• Minimal
interac3ons
with
food
and
drugs
• Non-­‐inferior
to
warfarin
for
preven3on
of
stroke
and
non-­‐
CNS
embolism
43

44. Rivaroxaban
Pharmacology
• ½
life
~13
hours
• Bioavailability
~80%
• Peak
plasma
level
in
2-­‐4
hours
• ~12
hours
in
pa3ents
>75,
5-­‐9
hours
(young
individuals)
• Metabolized
by
liver
• CYP3A4,
CYP3A5,
CYP2J2
• Excreted
by
Kidney
• Urine
66%
• Feces
33%
44

45. Apixaban
(Eliquis)
Bristol-­‐Myers
Squibb/Pfizer
• Oral,
direct,
selec3ve
factor
Xa
inhibitor
• No
forma3on
of
reac3ve
intermediates
• No
organ
toxicity
or
LFT
abnormali3es
in
chronic
toxicology
studies
• Low
likelihood
of
drug
interac3ons
or
QTc
prolonga3on
– Good
oral
bioavailability
– No
food
interac3ons
– Balanced
elimina3on
(~25%
renal)
– ½-­‐life
~12
hrs
• FDA
approval
12/28/2012
NH2
45
N
N
O N
N O
O
O

46. Fibrinoly3c
Agents
• Thromboly3c
(fibrinoly3c)
therapy
is
used
to
restore
vascular
patency
in
order
to
prevent
loss
of
3ssue,
limb,
and
organ
func3on
▫ Indica3ons
– AMI
– PE/DVT
– Thrombo3c
stroke
– PAD
– Occlusion
of
indwelling
catheter
46

47. Fibrinoly3c
Agents
▫ Mechanism
of
Ac3on
1. Acts
by
conver3ng
plasminogen
to
plasmin
2. Plasmin
lyses
clots
by
diges3ng
fibrin
contained
in
clots
47

48. Two
Classes
of
Fibrinoly3c
Agents
— Streptokinase
— 1st
thromboly3c
agent
— Derived
from
Streptococcus
— Long
half-­‐life
— Pa-ents
can
develop
an-bodies
Fibrin
— Urokinase
— Direct
ac3vator
of
plasminogen
— Derived
from
human
-ssue
culture
media
and
recombinant
deriva-ves
— Not
used
for
coronary
disease—more
commonly
used
for
catheter-­‐based
thrombosis
— tPA
— One
of
the
first
recombinant
forms
— Secreted
by
endothelial
cells
— Converts
plasminogen
to
plasmin
48 Non-­‐Specific
Fibrin
Specific

49. Catheter
Directed
Thrombolysis
(CDT)
• Objec3ves
of
– Iden3fy
underlying
lesion
– Dissolve
thrombus
and
restore
perfusion

50. Monitoring
Fibrinoly3c
Agents
• D-­‐Dimer
• FDP
• Euglobulin
Lysis
Time
• Plasminogen
• α2An3plasmin
• Plasminogen
ac3vator
inhibitor-­‐1
50

51. IVC
Filters
51
Indica3ons:
1. Pa3ents
in
whom
an3coagulant
therapy
is
contra-­‐indicated
2. When
an3coagula3on
therapy
is
not
working
Placed
below
the
junc3on
of
the
IVC
and
the
lowest
renal
vein

52. Atherosclero3c
Plaque
Disrup3on
and
Platelet
Ac3va3on
Mohler E. N Engl J Med 2007;357:293-296

53. An3platelet
Therapies
• Proven
efficacy
in
the
treatment
of
acute
thrombosis
and
preven-on
of
arterial
thrombosis
• However
they
do
increase
the
risk
of
bleeding
53
Target
Drug
Cyclooxygenase
inhibitors
Ø Aspirin
Ø NSAIDS
Ø Ibuprofen
(Motrin)
Ø Indomethacin
(Indocin)
Ø Naproxen
(Aleve)
ADP
receptor
antagonists
Ø Thienopyridines
Ø Ticlopidine
Ø Clopidogrel
GPIIb/IIIa
antagonists
Ø Abciximab
Ø Tirofiban
Ø Ep3fiba3de
Phosphodiesterase
inhibitors
Ø Dipyridamole

54. An3platelet
Drugs
Ø Cyclooxygenase
inhibitors
–
Aspirin
• Mechanism
of
ac3on
1. Irreversibly
inhibits
cyclooxygenase-­‐1
in
platelets
and
megakaryocytes
2. Blocks
the
forma3on
of
Thromboxane
A2
• Immediate
an-thrombo-c
effect
lasts
7-­‐10
days
a) Inhibi3on
of
COX-­‐1
achieved
with
low
doses
of
aspirin
b) Inhibi3on
of
COX-­‐2
requires
larger
doses
of
aspirin
• Pharmacokine3cs
– Absorbed
in
the
stomach
and
upper
intes3ne
– Peak
plasma
levels
• 30-­‐40
minutes
aper
inges3on
• 3-­‐4
hours
with
enteric-­‐coated
aspirin
– Inhibi3on
of
platelet
func3on
occurs
in
1
hour
54

55. An3platelet
Therapies:
Other
NSAIDS
COX-­‐1
Selec3ve
COX-­‐2
Selec3ve
• Transient
and
incomplete
inhibi3on
of
TXA2
• Tradi3onal
– Acetaminophen
• Does
not
inhibit
or
impair
platelet
func-on
– Indomethacin,
Ibuprofen,
Naproxen
• Inhibit
both
COX-­‐1
and
COX-­‐2
• Reversible
inhibi3on
• Designed
to
reduce
prostaglandin
synthesis
à
inflamma3on
• Do
not
have
an3platelet
ac3vity
• Do
not
inhibit
TXA2
ac3vity
• Block
PGI2
synthesis
in
endothelial
cells
• Celebrex,
Vioxx
• Rofecoxib
withdrawn
from
the
market
–
increases
risk
of
myocardial
infarc3on
3-­‐to-­‐5-­‐fold
numob.wnumob.wordpress.com/
2009/08/01/ordpress.com/2009/08/01/
ยา

56. An3platelet
Therapies:
Aspirin
• Adverse
effects
▫ Aspirin
Resistance—inability
of
aspirin
to:
1. Protect
individuals
from
thrombo3c
complica3ons
– Inability
to
reduce
TXA2
produc-on
in
pa-ents
– Clinical
aspirin
resistance
2. To
inhibit
TXA2-­‐dependent
platelet
aggrega3on
– In
one
or
more
in
vitro
“tests”
of
platelet
func-on
– Laboratory
(pharmacologic)
resistance
▫ Associated
with
upper-­‐GI
toxicity
▫ Note:
– Aspirin
does
not
cause
a
generalized
bleeding
abnormality
unless
given
to
pa-ents
with
an
underlying
– Hemosta-c
defect
– Uremia
– Concomitant
an-coagulant
therapy
56

57. Aspirin

58. Aspirin
on
Platelets
and
Endothelial
Cells
www.nbs.csudh.edu/chemistry/faculty/nsturm/
CHE452/10_Arachidon…

59. An3platelet
Drugs
ADP
receptor
antagonists
–
THIENOPYRIDINES
▫ ADP
ac3vates
platelets
by
binding
its
purinergic
P2Y1
and
P2Y12
receptors
– P2Y1
mediates
Ca2+
mobiliza3on,
shape
change
and
a
transient
reversible
aggrega3on
– P2Y12
induces
las3ng
aggrega3on
and
decrease
in
cAMP
Thienopyridines
1. Clopidogrel
(Plavix)
– Irreversibly
blocks
the
ADP
P2Y12
receptor
à
inhibi3on
of
gpIIb/IIIa
receptor
– Inhibits
platelet
aggrega3on
2. Ticlopidine
(Ticlid)
– Blocks
the
ADP
P2Y12
receptor
à
inhib3on
of
gpIIb/IIIa
receptor
– Inhibits
platelet
aggrega3on
and
release
59
Prasugrel
-­‐-­‐
Effient®
is
an
inhibitor
of
platelet
ac3va3on
and
aggrega3on
through
the
irreversible
binding
of
its
ac3ve
metabolite
to
the
P2Y12
class
of
ADP
receptors
on
platelets

60. An3platelet
Drugs
Ø GPIIb/IIIa
antagonists
Ø Block
the
gpIIb/IIIa
fibrinogen
binding
receptor
Ø Prevent
the
crucial
mechanical
step
in
aggrega3on
Ø Strongest
an3thrombo3c
poten3al
1. Abciximab
(ReoPro)
– Monoclonal
an3body
that
binds
to
the
IIb/IIIa
receptor
to
block
platelet
aggrega3on
2. Ep3fiba3de
(Integrelin)
– SyntheAc
cyclic
hexapep3de
derived
from
a
snake
venom
that
irreversibly
binds
the
IIb/IIIa
receptor
3. Tirofiban
(Aggrastat)
– SyntheAc,
non-­‐pep3de
inhibitor
of
IIb/IIIa
receptor
60

61. An3platelet
Drugs
Ø Phosphodiesterase
inhibitors
Ø Inhibit
platelet
aggrega3on
by
increasing
cAMP
Ø Elevated
cAMP
inhibits
platelet
func3on
ü Dipyridamole
(PersanAne)
– Inhibits
the
phosphodiesterase
enzymes
which
normally
break
down
cAMP
a. Increases
cAMP
▫ Blocks
platelet
response
to
ADP
▫ Inhibits
aggregaAon
response
to
collagen,
epinephrine,
ADP
b. Does
not
prolong
the
bleeding
3me
61

62. h^p://circ.ahajournals.org/content/123/7/798/F3.large.jpg

63. www.nature.com/nrd/journal/v9/n2/full/nrd2957.html