Drug Induced Coagulopathy 

Hemostasis has 3 major components:

Component

Targeted by Drugs

Platelets (Primary hemostasis)

Aspirin, clopidogrel, GP IIb/IIIa inhibitors

Coagulation cascade (Secondary hemostasis)

Heparin, warfarin, DOACs

Fibrinolysis

tPA, streptokinase


A. Heparin-Induced Coagulopathy

1. Unfractionated Heparin (UFH)

 Mechanism

  • Potentiates Antithrombin III
  • Inhibits:
    • Thrombin (IIa)
    • Factor Xa
    • IXa, XIa, XIIa

 Lab Pattern

  • ↑ aPTT(target—1.5–2.5 × control)
  • Normal PT
  • Normal platelets (unless HIT)
  • Anti-Xa elevated(target—>0.3–0.7 IU/mL)


 Clinical Clues

  • Bleeding at lines
  • Hematuria
  • Retroperitoneal bleed
  • Excessive surgical bleeding

 Management 

  • Stop heparin
  • Protamine sulfate
    • 1 mg neutralizes 100 units UFH (given in last 2–3 hrs)

Protamine adverse effects:

  • Hypotension
  • Anaphylaxis
  • Pulmonary hypertension
  • Bradycardia


  • Severe bleed → PCC/FFP (rarely needed)


2. Low Molecular Weight Heparin (LMWH)

Lab Pattern

  • aPTT usually normal
  • Anti-Xa assay diagnostic

Target Anti-Xa (Therapeutic):

  • 0.6–1.0 IU/mL (BID dosing)
  • 1.0–2.0 IU/mL (OD dosing)


Reversal

  • Protamine partially effective (~60%)


3. Fondaparinux-Induced Bleeding

Example:

  • Fondaparinux


Mechanism

  • Synthetic pentasaccharide
  • Indirect factor Xa inhibitor
  • Does NOT inhibit thrombin
  • 100% renal excretion
  • Long half-life (~17 hours)


Risk Factors

  • CrCl <30 → contraindicated
  • Elderly
  • Low body weight (<50 kg)
  • Concomitant anticoagulants


Monitoring

  • No routine monitoring
  • Anti-Xa assay (fondaparinux-calibrated)


Reversal of Fondaparinux

There is NO specific antidote.

Management:

  • Stop drug
  • PCC (4-factor) – most commonly used
  • rFVIIa (rescue therapy)
  • Supportive transfusion

Protamine  ineffective

Dialysis  ineffective


B. Warfarin

Mechanism

  • Inhibits Vitamin K epoxide reductase
  • Affects Factors: II, VII, IX, X, Protein C, S

Lab Pattern

  • ↑ PT / INR
  • aPTT mildly ↑
  • Platelets normal

Causes of Toxicity in ICU

  • Antibiotics (↓ gut flora)
  • Liver dysfunction
  • Drug interactions (amiodarone)
  • Renal failure

Reversal Strategy (Based on ASH/ACCP Guidelines)

Situation

Management

INR >10, no bleed

Oral Vitamin K

Major bleeding

4-factor PCC + IV Vitamin K

Life-threatening

PCC preferred over FFP



C. Direct Oral Anticoagulants (DOACs)

Includes:

  • Dabigatran (Direct thrombin inhibitor)
  • Apixaban, Rivaroxaban, Edoxaban (Factor Xa inhibitors)

Lab Pattern

  • PT/aPTT unreliable
  • Anti-Xa assay (drug specific)
  • Thrombin time prolonged (dabigatran)

Reversal

Drug

Antidote

Dabigatran

Idarucizumab

Factor Xa inhibitors

Andexanet alfa((Dose based on last dose & timing of FXa inhibitor.)

If unavailable

PCC


 

Antiplatelet Drug–Induced Coagulopathy

Feature

Aspirin

P2Y12 Inhibitors(Clopidogrel, Ticagrelor, Prasugrel)

GP IIb/IIIa Inhibitors (Abciximab, Eptifibatide, Tirofiban)

Target Site

COX-1 enzyme

ADP (P2Y12) receptor

Final common pathway (GP IIb/IIIa receptor)

PT / aPTT

Normal

Normal

Normal

Platelet Count

Normal

Normal

May fall (drug-induced thrombocytopenia possible)

Bleeding Time

Prolonged

Prolonged

Markedly prolonged

Common ICU Bleeding

GI bleed

Surgical site bleed

Access site bleed, severe procedural bleed

Reversal – Mild Bleed

Stop drug

Stop drug

Stop infusion

Reversal – Severe/Life-Threatening Bleed

Platelet transfusion

Platelet transfusion (limited if recent dose)

Platelet transfusion (more effective with eptifibatide/tirofiban than abciximab)

Specific Antidote

None

None

None


Fibrinolytic-Induced Coagulopathy

Drugs:

  • Alteplase
  • Tenecteplase
  • Streptokinase

Mechanism

  • Convert plasminogen → plasmin
  • Fibrin degradation
  • ↓ fibrinogen

Lab Pattern

  • ↓ fibrinogen
  • ↑ D-dimer
  • PT/aPTT prolonged

Complication

  • Intracranial hemorrhage (most feared)

Reversal

  • Cryoprecipitate (target fibrinogen >150 mg/dL)
  • Tranexamic acid
  • Platelets if low


 Drug-Induced Thrombocytopenia

Mechanisms:

  • Immune destruction
  • Bone marrow suppression
  • TMA (Drug-induced TTP)

Common Drugs

  • Heparin (HIT)
  • Linezolid
  • Valproate
  • Chemotherapy
  • Quinine
  • Beta-lactams

ICU Clue

  • Sudden platelet drop after drug exposure

 Pattern Recognition Table 

Lab Pattern

Likely Drug

↑ aPTT only

Heparin

↑ PT only

Warfarin

Normal PT/aPTT + bleeding

Antiplatelet

↓ Platelets + thrombosis

HIT

↓ Fibrinogen + ↑ D-dimer

tPA