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Focus on
PHARMACOLOGY
ESSENTIALS FOR HEALTH PROFESSIONALS
CHAPTER
23
Anticoagulants
Multimedia Directory
Slide 17
Slide 25
Mechanism of Action of Heparin Animation
Mechanism of Action of Warfarin Animation
Focus on Pharmacology: Essentials for Health Professionals, Second Edition
Jahangir Moini
Hemostasis:
Three Events After Injury
1. Vascular spasms: platelets release
serotonin, which causes blood vessel
to spasm and decrease blood loss until
clotting occurs
2. Platelet plug: platelets become sticky
and adhere to vessel lining and each
other, forming platelet plug, which is
invaded by clotting factors
Focus on Pharmacology: Essentials for Health Professionals, Second Edition
Jahangir Moini
Hemostasis:
Three Events After Injury
3. Coagulation: clot forms through
chemical reactions that create netlike
structure of fibrin, sealing off opening
in injured vessel
Focus on Pharmacology: Essentials for Health Professionals, Second Edition
Jahangir Moini
Figure 23-1 Hemostasis begins when a blood vessel is damaged and ends when the
fibrin threads trap blood cells, forming a clot that seals the injured vessel.
Focus on Pharmacology: Essentials for Health Professionals, Second Edition
Jahangir Moini
Figure 23-2
Basic steps of hemostasis.
Focus on Pharmacology: Essentials for Health Professionals, Second Edition
Jahangir Moini
Mechanism of Action: Hemostasis
• Involves 11 plasma proteins (clotting
factors)
• Most clotting proteins synthesized by
liver
• Prothrombin activator, prothrombin,
thrombin, fibrinogen, fibrin
Focus on Pharmacology: Essentials for Health Professionals, Second Edition
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Figure 23-3
The steps in the coagulation cascade.
Focus on Pharmacology: Essentials for Health Professionals, Second Edition
Jahangir Moini
Anticoagulants
• Medications that prolong bleeding time
• Do not dissolve clots already formed,
but may prevent clots from becoming
larger
• Used to treat MI, venous thrombosis,
pulmonary emboli
• Primarily used for thrombosis in veins
Focus on Pharmacology: Essentials for Health Professionals, Second Edition
Jahangir Moini
Table 23-1
Anticoagulants
Focus on Pharmacology: Essentials for Health Professionals, Second Edition
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Heparin: Uses
• Works by increasing length of
coagulation; inhibits thrombi from
forming or growing larger
• Treat emboli, thrombi, MI, and to
prevent clotting during open-heart
surgery, coronary artery bypass graft,
and dialysis
Focus on Pharmacology: Essentials for Health Professionals, Second Edition
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Heparin: Adverse Effects
• Hemorrhage in urinary or GI tracts,
subdural hematomas, hemorrhagic
pancreatitis, hemarthrosis, ecchymosis
Focus on Pharmacology: Essentials for Health Professionals, Second Edition
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Heparin: Contraindications
• Contraindicated in serious and
intracranial bleeding, severe liver or
kidney disease, malignant hypertension
• Interacts with aspirin, NSAIDs,
anesthetics, valproic acid,
thrombolytics, and other drugs
Focus on Pharmacology: Essentials for Health Professionals, Second Edition
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Heparin: Patient Information
• Teach patients how to administer
heparin subcutaneously.
• Advise patients to protect themselves
from injury (e.g., use electric shaver).
• Warn patients to avoid aspirin and
other OTC drugs.
• Instruct patients to report signs of
bleeding.
Focus on Pharmacology: Essentials for Health Professionals, Second Edition
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Heparin in Older Adults
• Older adults are more susceptible to
effects of anticoagulants. Signs of
overdose include epistaxis, blood in
stool or urine, excessive bruising, and
prolonged bleeding.
• Overdose can be treated by slow
infusion of 1% protamine sulfate.
Focus on Pharmacology: Essentials for Health Professionals, Second Edition
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Figure 23-4
Mechanism of action of anticoagulants.
Focus on Pharmacology: Essentials for Health Professionals, Second Edition
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Mechanism of Action of Heparin
Animation
Click on the screenshot to view an animation showing the mechanism of
action of heparin.
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LMWH: Uses
• Greater bioavailability and longer action
than heparin
• More effective in preventing and
treating venous thromboembolism
• Less bleeding and fewer episodes of
heparin-induced thrombocytopenia
Focus on Pharmacology: Essentials for Health Professionals, Second Edition
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Table 23-2
Common Low-Molecular-Weight Heparins
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Warfarin (Coumadin): Uses
• Interferes with hepatic synthesis of
vitamin K-dependent clotting factors
(II, VII, IX, X)
• Used on inpatient and outpatient basis
for long-term anticoagulation
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Warfarin: Adverse Effects
•
•
•
•
•
•
Hemorrhage
Diarrhea
Urticaria
Alopecia
Skin necrosis
Dermatitis
Focus on Pharmacology: Essentials for Health Professionals, Second Edition
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Warfarin: Contraindications
• Contraindicated in active or previous
ulceration, hepatic or renal disease,
malignant hypertension, bacterial
endocarditis, chronic alcoholism,
pregnancy
• Interacts with hepatic enzyme
inhibitors, aspirin, NSAIDs, and
thrombolytics
Focus on Pharmacology: Essentials for Health Professionals, Second Edition
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Warfarin: Patient Information
• Instruct patients to report signs of
bleeding; chest, abdominal, lumbar, or
pelvic pain.
• Advise patient to stop drug immediately
if signs of hepatitis occur.
• Advise female patients to avoid
pregnancy with barrier contraceptive
and to avoid breastfeeding.
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Warfarin Tips for Patients
• Advise patients that 5 days prior to
dental procedures, warfarin should be
stopped.
• Supplemental intake of vitamin K can
potentiate or inhibit oral
anticoagulants.
Focus on Pharmacology: Essentials for Health Professionals, Second Edition
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Mechanism of Action of Warfarin
Animation
Click on the screenshot to view an animation showing the mechanism of
action of warfarin.
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Antiplatelets: Uses
• Prevent platelets from binding together
• Used to prevent clot formation in
arteries, in MI and stroke, and in PCTA
• Aspirin: low doses inhibit platelet
aggregation and prolong bleeding time
• Ticlopidine (Ticlid) and clopidogrel
(Plavix) irreversibly inhibit platelet
activation
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Antiplatelets: Uses
• Abciximab (ReoPro), eptifibatide
(Integrilin) and tirofiban (Aggrastat)
interrupt interaction of fibrinogen with
clotting factors
Focus on Pharmacology: Essentials for Health Professionals, Second Edition
Jahangir Moini
Table 23-3
Antiplatelet Agents
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Antiplatelets: Adverse Effects
• Epigastric pain, heartburn, nausea,
diarrhea, major or minor bleeding
• Abciximab: cardiac arrhythmias,
abnormal thoughts, dizziness
Focus on Pharmacology: Essentials for Health Professionals, Second Edition
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Antiplatelets: Contraindications
• Contraindicated in patients with history
of peptic ulcer, hypertension, asthma,
allergies, nasal polyps
• Interact with anticoagulants,
thrombolytic agents, dextran, and other
drugs
Focus on Pharmacology: Essentials for Health Professionals, Second Edition
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Antiplatelets:
Patient Information
• Instruct patients to report nausea,
diarrhea, rash, sore throat, or
infections; signs of bleeding; signs of
hepatitis.
• Advise patients to avoid aspirin and
antacids.
Focus on Pharmacology: Essentials for Health Professionals, Second Edition
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Garlic as Anticoagulant
• Garlic has been shown to decrease
platelet aggregation.
• Use of garlic with anticoagulants may
increase risk of bleeding complications.
Focus on Pharmacology: Essentials for Health Professionals, Second Edition
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Thrombolytics: Uses
• Used to prevent or treat excessive
bleeding from surgical sites
• Facilitate conversion of plasminogen to
plasmin, which hydrolyzes fibrin to
dissolve blood clots
• Also called plasminogen activators
Focus on Pharmacology: Essentials for Health Professionals, Second Edition
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Table 23-4
Thrombolytics
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Thrombolytics: Adverse Effects
• Common: bleeding caused by
fibrinogenolysis or fibrinolysis at site of
injury
• Serious: intracranial bleeding
Focus on Pharmacology: Essentials for Health Professionals, Second Edition
Jahangir Moini
Thrombolytics: Contraindications
• Contraindicated in active bleeding,
pregnancy, lactation, intracranial
trauma, vascular disease, and cancer
• Interact with anticoagulants, aspirin,
and herbs such as feverfew, ginger,
and ginkgo
Focus on Pharmacology: Essentials for Health Professionals, Second Edition
Jahangir Moini
Thrombolytics:
Patient Information
• Instruct patients to report signs of
bleeding or changes in consciousness.
• Advise women to avoid breastfeeding.
Focus on Pharmacology: Essentials for Health Professionals, Second Edition
Jahangir Moini
Thrombocytopenia
• Platelet deficiency; most common
cause of abnormal bleeding
• Hemophilia applies to several
hereditary bleeding disorders that
result from lack of factors needed for
clotting.
Focus on Pharmacology: Essentials for Health Professionals, Second Edition
Jahangir Moini