User:Ahlam R. Jumah/sandbox

== Heparin therapy

Doses and monitoring
== Mechanism of action : The molecular basis for the anticoagulant action of heparin lies in its ability to bind to and enhance the inhibitory activity of the plasma protein antithrombin against several serine proteases of the coagulation system, most importantly factors IIa (thrombin), Xa and IXa. Two major mechanisms underlie heparin's potentiation of antithrombin. The conformational changes induced by heparin binding cause both expulsion of the reactive loop and exposure of exosites of the surface of antithrombin, which bind directly to the enzyme target; and a template mechanism exists in which both inhibitor and enzyme bind to the same heparin molecule. The relative importance of these two modes of action varies between enzymes. In addition, heparin can act through other serine protease inhibitors such as heparin co-factor II, protein C inhibitor and tissue factor plasminogen inhibitor. The antithrombotic action of heparin in vivo, though dominated by anticoagulant mechanisms, is more complex, and interactions with other plasma proteins and cells play significant roles in the living vasculature.

Dosage 1/ Obtain patient’s height and weight. If weight is >130% of ideal body weight (IBW) use dosing weight for heparin dosing. Contact pharmacist for all heparin dose calculations. Dosing Weight= IBW+ (actual body weight-IBW) x 0.4      [Calculated by program]. 2/ Obtain aPTT prior to heparin therapy. If levels elevated, call MD. 3/ Obtain CBC prior to heparin therapy. If PLT, HGB, HCT low contact MD. 4/

Loading Dose : -heparin 80 units/kg IV push for PE/DVT age <70. - heparin 70 units/kg IV push PE/DVT (age >70) or TIA/CVA (max of 5000 units). -heparin 60 units/kg IV push ACS (max of 5000 units). 5/ Initial Maintenance Dose: Start heparin infusion (25,000 units/250 ml) using IV pump Begin immediately after loading dose. By options as below : _ 18 units/kg/hr in DVT age < 70. _ 15 units/kg/hr CVA/TIA or DVT age > 70. _ 12 units/kg/hr ACS - Maximum infusion rate of 1000 units/hr. 6/ Obtain aPTT 6 hours after start of heparin infusion.

Missed Dose If you miss a dose of this medicine, take it as soon as possible. However, if it is almost time for your next dose, skip the missed dose and go back to your regular dosing schedule. Do not double doses.

side effects Heparin, first used to prevent the clotting of blood in vitro, has been clinically used to treat venous thrombosis for more than 50 years. Although several new anticoagulant drugs are in development, heparin remains the anticoagulant of choice to treat acute thrombotic episodes. The clinical effects of heparin are meritorious, but side effects do exist. Bleeding is the primary untoward effect of heparin. Major bleeding occurs in 1% to 33% of patients who receive heparin therapy.45 Additional important untoward effects of heparin therapy that are discussed in this article include heparin-induced thrombocytopenia (HIT), heparin-associated osteoporosis (HAO), eosinophilia, skin reactions, allergic reactions other than thrombocytopenia, and alopecia. Other side effects include frequent abnormalities of hepatic function tests and occasional hyperkalemia.

Monitoring :
 * The UFH anticoagulant response is monitored using APTT, a measurement that is sensitive to inhibition of thrombin and FXa.
 * Anti-Xa activity measurement is the most widely used examination for LMWH therapy management.