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THROMBOCYTOPENIA                       See Heparin-induced Thrombocytopenia 2006

A. Production defect
1. Reduced thrombopoiesis megakaryocytes

2. Defective maturation (normal or increased megakaryocytes)

B. Sequestration (distribution disorder)
1. Splenomegaly

2. Hypothermic anesthesia

C. Accelerated destruction
1. Immunologic

2. Non immunologic

D. Loss by hemorrhage & massive transfusion

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Causes of Thrombocytopenia

  1. Drugs: chemotherapy, heparin, chloramphenicol, Ticlopidine, Clozepine, H2-blockers
  2. Autoimmune :  a. Previously called idiopathic    b. May follow viral infection
  3. Splenomegaly: liver failure, malignancy, infection
  4. Viral: follows infection. ? Autoimmune. Associated with CMV, HIV
  5. Isoimmune: in neonates, mother makes anti-platelet antibody
  6. Neoplastic: infiltration of bone marrow prevents platelet development
  7. Aplastic Anemia: pancytopenia; viral, idiopathic, autoimmune, chloramphenicol
  8. Thrombotic thrombocytopenic purpura (TTP): with hemolysis, fever, mental status changes
  9. Disseminated intravascular coagulopathy (DIC): consumptive coagulopathy
  10. HIV Related
  11. HELLP Syndrome: Follows pregnancy. Low platelets
  12. Hereditary Disorders


What is the best way to determine if thrombocytopenia in a patient on multiple medications is drug-induced?
CCJM  March 2002

Approach to suspected drug-induced thrombocytopenia:
Annals IM 1998:129:886 George JN; Ann ls IM 2001; 134:346 Rizvi MA

  1. Stop all drugs for which there is no clear or present indication; postulate drug most likely causing thrombocytopenia
  2. stop drug most likely causing thrombocytopeniaand substitute a chemically unrelated compound for its indication
  3. Observe for improvement; if improvement does not occur promptly, choose next most likely drug, substitute for it as above, and repeat cycle until thrombocytopenia resolves.

Common noncytotoxic drugs with definite or probable evidece for causing thrombocytopenia:
Annals IM 2001;134:346  Rizvi MA, George JN;   Annals IM 1998:129:886 George JN

Anti-inflammatory, analgesics


Cardiovascular drugs

Central nervous system drugs

Endocrine drugs

Gastrointestinal drugs

Renal drugs

Other drugs

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For low platelets, how low is dangerous?
The answer depends on the cause of the thrombocytopenia and on whether surgery or childbirth is planned.

J.N. GEORGE -  Cleveland Clnic J ofo Med  Vol 71. April 2004  p. 277