anticoagulation drugs.txt

it has a pentasaccharide sequence which potentiates the action of antithrombin III: that INACTIVATES IIa and Xa

• rapid initiation of anticoagulation needed
• used to maintain anticoag until warfarin is EFFECTIVE (NB warf takes time)

heparin (LMWH) and not warfarin as warfarin is teratogenic

used as a 'bridging anticoagulation' in patients with mechanical heart valves who are having non cardiac surgery and their warfarin is stopped for this

inhibits vitamin K epoxide reductase: so inhibits vit K dependent gamma carboxylation of factors 2, 7, 9, 10

prolonged, reflecting the half life of the factors

• 6 months
• INR: 2.5

• lifelong
• INR: 2.5

• lifelong
• INR: 3.5

• 6 weeks before and after
• INR: >2.0

• lifelong
• INR: 2.5

• lifelong
• INR: 3.75

• 1. active bleeding
• 2. bleeding disorder
• 3. pregnancy: esp. 1st trimester and last 4 weeks
• 4. surgery for SOL in CNS

• 1. history of bleed e.g. from ulcer
• 2. pregnancy
• 3. uncontrolled hypertension
• 4. high risk of head injury: epilepsy/falls (esp. elderly)
• 5. poor compliance e.g. IVDU

• cholestyramine
• decreased absorption of warfarin so less effect

• rifampicin and carbamazepine: increase warfarin metabolism so less warf effect
• amiodarone and erythromycin: decrease warfarin metabolism so more warf effect

• loading dose often used for day1 and 2
• dose adjustment according to INR which is measured daily for 4-5days
• once got stable dose, monitor every 2-12 weeks
• can get home testing of INR

• DO NOT GIVE VIT K immediately! because it may be difficult to re-anticoag for a week or 2!
• only give vitK if major active bleed: 0.5-1mg
• normally if over anticoag give: PCC (prothrombin complex concentrate) or FFP
• this reverses warfarin effect RAPIDLY but TRANSIENTLY

• 1. acute STEMI: pt within 12 h onset chest pain with STE/new LBBB and no contraindications
• Rx: streptokinase or alteplase (tPA)
• 2. acute ischaemic stroke: present within 3h onset of symptoms, ICH excluded on imaging and no CI
• Rx: tPA (not streptokinase)
• 3. major PE with haemodynamic disturbance (drop BP)
• Rx: tPA/streptokinase but lower dose than STEMI

• tPA is clot selective as it activates plasminogen BOUND to fibrin
• whereas streptokinase binds BOTH free and bound plasminogen

• B haemolytic strep
• so antistrep Ab will neutralise it!