Anticoagulation – ( Pharmacology)

Anticoagulation:

Drugs that prevent blood coagulation and stop the occurrence or expansion of a thrombus.

Classification:

1. Vitamin K antagonist – Warfarin.

2. Heparin and related drugs:

(a) Heparin.

(b) LMWH (Enoxaparin, Dalteparin, Tinzaparin).

(c) Synthetic heparin derivatives (Fondaparinux – longer acting).

3. Direct thrombin inhibitors:

(a) Parenteral → Hirudin, Lepirudin, Argatroban, Bivalirudin.

(b) Oral → Dabigatran.

4. Active factor Xa inhibitor → Rivaroxaban, Apixaban.

Warfarin:

• Competitively inhibits vitamin K epoxide reductase and inhibits the post-translational carboxylation of glutamate residues on vitamin K dependent coagulation factors II (prothrombin), VII, IX, and X.

Heparin:

• Antithrombin III-Irreversibly inactivates thrombin and factor Xa.
• Heparin potentiates anti-thrombin III activity.

Advantages of LMWH:

1. Can be administered s.c.

2. Effects are consistent and dosing less frequent (Long t1/2 and eliminate. By 1st order kinetics).

3. Dose is given in mg (not in units) can be easily calculated on a bodyweight basis.

4. Chance of hemorrhage is less.

5. Risk of osteoporosis is decreased.

	Heparin	Warfarin
Route of administration	I.v., S.c.	Oral
Onset of action	Immediate	Delayed
Mechanism	Activ. Of AT-III	Decrease activ. Of c.f. 2,7,9,10
Antagonist	Protamine sulphate	Vitamin K
Use	To initiate therapy	For maintenance

Uses of anti-coagulants:

1. Myocardial infarction

2. Unstable angina

3. Rheumatic heart disease

4. Cerebrovascular disease

5. Haemodialysis

6. Defibrination syndrome (DIC).

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