Page 392 - Essential Haematology

378 / Chapter 27 Thrombosis and antithrombotic therapy

Table 27.9 Contraindications to thrombolytic Table 27.10 Antiplatelet therapy in patients
therapy. with an acute coronary syndrome and in
those undergoing percutaneous coronary
Absolute Relative intervention ( PCI ). (After Lange R.A. and Hillis
contraindications contraindications L.D. (2004) N Engl J Med 350 , 277 – 80.)
Active gastrointestinal Traumatic
Target/patient
bleeding cardiopulmonary
Drug group Duration
Aortic dissection resuscitation
Head injury or Major surgery in the Acute coronary syndrome
cerebrovascular past 10 days Aspirin All Life - long
accident in the past Past history of Clopidogrel All 9 – 12 months
2 months gastrointestinal
Glycoprotein IIb/IIIa inhibitors
Neurosurgery in the bleeding
Abciximab None –
past 2 months Recent obstetric
Eptifi batide High risk 48 – 72 hours
Intracranial aneurysm delivery
or neoplasm Prior arterial puncture Tirofi ban High risk 48 – 72 hours
Proliferative diabetic Prior organ biopsy Patients undergoing PCI
retinopathy Serious trauma Aspirin All Life - long
Severe arterial
Clopidogrel All 9 – 12 months
hypertension
Abciximab High risk 12 hours after
(systolic pressure
PCI
> 200 mmHg, diastolic
Eptifi batide High risk 18 – 24 hours
pressure
after PCI
> 110 mmHg)
Tirofi ban None –
Bleeding diathesis

Recombinant tissue plasminogen activator has a have a history of coronary artery or cerebrovascular
particularly high affi nity for fibrin and this allows disease. It may also be useful in preventing throm-

lysis of thrombi with less systemic activation of bosis in patients with thrombocytosis.
fi brinolysis. Clopidogrel Th is adenosine diphospate
(ADP) receptor antagonist (Fig. 27.8 ) is an antiplate-
let agent used for reduction of ischaemic events in
patients with ischaemic stroke, myocardial infarc-
Antiplatelet d rugs
tion or peripheral vascular disease. It is used after
Antiplatelet agents are gaining an increasing role in coronary artery stenting or angioplasty and in
clinical medicine. It is now clear that aspirin is valu- patients requiring long - term antiplatelet therapy
able in the secondary prevention of vascular disease. who are intolerant or allergic to aspirin.
®
Several other agents are being used for diff erent Dipyridamole (Persantin ) Th is drug is a

indications (Table 27.10 ). The sites of action of the phosphodiesterase inhibitor thought to elevate
antiplatelet drugs are illustrated in Fig. 27.8 . cyclic adenosine monophosphate levels in circulat-
Aspirin Aspirin inhibits platelet cyclo - ing platelets which decreases their sensitivity to acti-
oxygenase irreversibly, thus reducing the production vating stimuli. Dipyridamole has been shown to
of platelet thromboxane A 2 . Low - dose therapy (e.g. reduce thromboembolic complications in patients
75 mg/day) has lesser risk of gastrointestinal bleed- with prosthetic heart valves and to improve the

ing and is most commonly used in patients who results in coronary bypass operations.