Mechanism of Drug Interactions

1.      Metabolism Interaction (Pharmacokinetic) (of Warfarin/ vit K inhibitors)

(disulfiram, clopidogrel, amiodarone)

¯

Inhibits CYP2C9 (Responsible for Warfarin Metabolism)

¯

¯ Metabolism of Warfarin

¯

­ Risk of Haemorrhage

2.      Pharmacodynamic Interactions:

Synergistic or Antagonistic Effect by another drug.

Heparin

¯

Inhibition of Factor IIa and Xa

¯

No blood Coagulation + Aspirin (blood thinner)

¯

Risk of bleeding

Adverse Drug Reactions of Oral anticoagulants

1. Risk of Bleeding

2. Rash

3. Impaired Hepatic Function

4. Hyperthyroidism

5. Congestive Heart Failure

6. Gastric Ulcer haemorrhage


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