EDTA, dipotassium salt, dihydrate: EDTA is an inhibitor of metalloproteases, at effective concentrations of 1-10 mM. EDTA acts as a chelator of the zinc ion in the active site of metalloproteases and can also inhibit other metal ion-dependent proteases such as calcium-dependent cysteine proteases. EDTA may interfere with biological processes which are metal-dependent.2 For use as an anticoagulant, disodium or tripotassium salts of EDTA are most commonly used. The optimal concentration is 1.5 mg per ml of blood. EDTA prevents platelet aggregation and is, therefore, the preferred anticoagulant for platelet counts.3 Using a 2% EDTA solution, 1-2 drops per ml of whole blood can be used as an anticoagulant.