Indications for anticoagulants Flashcards
what to check when prescribing anticoagulants
risk of stroke or bleeding. use Chadsvasc scoring system to find out if they are at risk stroke. benefits must be great enough to justify the risk. HASBLED score to find out if at risk of bleeding.
characteristics of ideal anticoagulant
oral, no need for monitoring, no interaction with food or drugs, given once or twice a day/ fixed dose irrespective of age and weight, as effective as warfarin, safer than warfarin
vitamin K antagonist
warfarin. vitamin K important co factor in clotting factors so reducing that will lead to less clotting
direct thrombin inhibitor
dabigatran
direct Xa inhibitors
rivaroxaban, apixaban, edoxaban
problems with warfarin
narrow therapeutic index, no standard dose, bleeding, interaction with multiple other drugs, teratogenic, avoid in pregnancy
INR
international normalised ratio, actual prothrombin time over standard prothrombin time. normal is 1 but is normally between 2.5 and 4
ways that drugs increase warfarin activity
decrease binding to albumin, inhibit degradation, decrease synthesis of clotting factors, inhibit platelets, inhibit clotting factors
ways that drugs decrease warfarin activity
induction of metabolising enzymes (cytochrome P450), promote clotting factor synthesis, reduced absorption
inhibitors of cytochrome P450
omeprazole, disulfiram, erythromycin, valproate, isoniazid, ciprofloxacin, cimetidine, ethanol (acutely) , sulphonamides
inducers of cytochrome P450
alcohol (chronic use), barbiturates, carbamazepine, phenytoin, rifampicin, sulphonylureas
best anticoagulants non warfarin
dabigatran, rivaroxiban, apixaban
other cardiovascular indications for anticoagulation
metallic heart valves, DVT/PE treatment, prophylaxis- surgery, high risk medical patients, immobilisation
