Transcript Louw
Oral anticoagulation Illse Louw Contents • • • • What you should know Cows and rats and creepy crawlies INR Stats What you should know • Warfarin is an oral anticoagulant • It prolongs the time taken for blood to clot • This reduces the possibility of clot formation – To prevent harmful blood clots from forming – To prevent worsening of existing clots • Too little warfarin – will not prevent clotting • Too much warfarin – possible bleeding complications What you should know • • • • Take the tablets once a day preferably in evening The dose must be taken as prescribed The dose must be monitored with regular lab tests Keep written record of your target INR, INR results and dosage • Regular INR tests – What is an INR – What is my INR therapeutic target • Testing intervals What you should know • Be aware of possible bleeding / thrombotic complications, report • Keep Vit K content of diet consistent – Avoid changes to normal eating patterns – Continue to eat a balanced diet – Vit K rich foods – cauliflower, cabbage, broccoli, spinach, brussel sprouts, avocado, liver • Be aware of drug and intercurrent illness interactions What you should know • Avoid heavy or binge drinking – Moderate is OK • Inform health care professional – Miss a dose or doses – Change diet or medication – Surgical or dental procedure planned – Pregnancy • Travel Of rats and cows and humans • Schofield FW (1924). "Damaged sweet clover; the cause of a new disease in cattle simulating haemorrhagic septicemia and blackleg". J Am Vet Med Ass 64: 553–6. • Roderick LM (1931). "A problem in the coagulation of the blood; "sweet clover disease of the cattle"". Am J Physiol 96: 413–6 • Stahmann MA, Huebner CF, Link KP (1941). "Studies on the hemorrhagic sweet clover disease. V. Identification and synthesis of the hemorrhagic agent". J Biol Chem 138 (2): 513–27 • Dicumarol patented in 1941 • Warfarin patented with Wisconson Alumni Research Foundation – Initially used as rodenticide – 1950’s used in humans Indications and target INR • Prescribed for conditions such as – Irregular heart rhythm, artificial heart valves, stroke ; Clotting in veins • Guidelines: – British Committee for Standards in Haematology 2011 – American College of Chest Physicians 2012 – Southern African Society of Thrombosis and Haemostasis SAMJ 2007 97 1259 Worldwide – patients on warfarin Country Population Patients on OAT Canada England France Italy Netherlands Spain USA 32 million 63 million 60 million 60 million 16,3 million 42 million 280 million 275 000 750 000 600 000 650 000 325 000 400 000 2,5 million J Thromb Thrombolysis 2006 21 73 0.9% 1.2% 1% 1.1% 2% 1% 0.9% Test for effect of warfarin ISI Patient PT INR Control PT SSW stats • • • • 699 patients INR < 2: 30% INR2-4: 65% INR > 4: 5% 100 90 80 70 63.8% 60 50 Series1 40 30 20 10 0 1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31 33 35 Make oral anticoagulants more convenient • Increase dose interval – British Guidelines agree with longer intervals – US 2008 guidelines – 4 wks – US 2012 12 wkly intervals • For patients taking VKA with consistently stable INRs we suggest and INR testing freq of up to 12 weeks • Unsuitable patients – congestive heart failure, other major disease developing – Leads to fewer dose changes Make oral anticoagulants more convenient • Do not correct if one INR out of range • Stable patients – no change for 3 months • Then INR = 1.5-1.9 Extra dose Versus Continue with usual 3.1-4.4 Withhold dose or Versus Usual INR @ 2 weeks 60% in TR 56% in TR … the future …. new oral anticoagulants