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warfarin therapy
| Question | Answer |
|---|---|
| warfarin indication | prevention or treatment of thromboembolism |
| conditions for warfarin use | VTE, A fib, stroke, mechanical heart valves |
| usual starting dose of warfarin | 5mg po qd (2.5-10mg range) |
| start lower dose if | pt over 65y/o, abnormal liver fxn, malnourished, low vitamin K intake, recent surgery, medications inducing warfarin |
| subsequent warfarin dosing | based on INR |
| normal PT | 10-13seconds |
| INR reference | 1 |
| goal INR normally | 2.0-3.0 |
| goal INR mechanical valves | 2.5-3.5 |
| goal INR prior to surgery | <1.5 |
| INR monitoring: inpatient | every 1-3 days |
| INR monitoring: outpatient | within 3-5 days every 4 weeks once stable |
| warfarin monitoring | BLEEDING s/sx of thrombus |
| warfarin adverse effects | bleeding, alopecia, cold intolerance, skin necrosis, purple toe syndrome, rash, jaundice, vertebral and rib fractures |
| warfarin metabolism | CYP3A4 and CYP2C9 |
| warfarin in hypothyroidism | increase dose |
| warfarin in hyperthyroidism | decrease dose |
| hypothyroid | more likely to clot |
| hyperthyroid | more likely to bleed |
| warfarin inducers | alcoholic grizly dic nabed (a) car (to) run phen phen |
| warfarin inhibitors | bac met ami (and) left the sorority assholes (to) make icy flowers sometimes |
| platelet fxn inhibitors | ASA NSAIDS, COX II inhibitors, acute alcohol |
| reduce GI flora synt of vitamin k | antibiotics |
| reduce GI absorption | cholestyramine, sucralfate |
| change protein binding | leflunamide, bactrim, alcohol |
| APAP | limit to <2g daily and short term |
| OTC warfarin interactions | boost, one a day (vit K) alka seltzer (ASA) |
| how much vitamin K to change INR 1 IU? | 714mcg weekly |
| herbals that inc. INR | garlic, ginger, chondroitin, glucosamine, horse chestnut, milk thistle, saw pamento, flax seed, fish oil |
| herbals that dec. INR | CoQ10, st. john's wort, green or herbal teas |
| herbals that are unpredictable on INR | ginseng |
| if adding warfarin to regimen | titrate to desired INR |
| adding if warfarin is already part of regimen | may see large fluctuations in INR so monitor it closely |
| long term/short term offender use | stabalize INR/monitor without dose change |
| when to check INR followin initiation or discontinuation of a drug | 3 days following |
| warfarin with inducer | increase warfarin dose |
| warfarin with inhibitor | decrease warfarin dose |
| dietary vitamin K sources | green vegetables, mayo, oils, soymilk,boost type deals |
| inpatient subtheraputic INR | give 1 additional "booster" dose *do not change weekly maintenance dose |
| outpatient subtheraputic INR | increase by fraction of weekly dose (10-20%) check for transient factors |
| inpatient supratheraputic INR | hold one dose adjust daily warfarin dose |
| outpatient supratheraputic INR | hold at least one dose decrease weekly dose (10-20%) |
| CHEST recommendations INR 3.0-5.0 | if no bleeding, hold dose(s) decrease weekly dose by 0-10% -if transient factor no dose reduction |
| CHEST recommendations INR >5.0-9.0 | if no bleeding, hold dose(s) decrease weekly dose by 10-20% can consider po vit.K 1mg - 2.5mg if at high risk for bleeding |
| CHEST recommendations INR >9.0 | if no bleeding, hold dose(s) give po vit.K 2.5-5mg, reduce dose of warfarin once restarted |
| serious supratheraputic INR and bleed | hold warfarin, IV vit.K 10mg by slow infusion supplement with frozen plasma, prothrombin complex, or recombinant factor VIIa repeat vit.K in 12 hours if persisten elevated INR |
| vitamin K, Phytonadione (mephyton) | vit. k for clotting factors |
| vit.K oral route | onset 6-12 hours INR theraputic in 24-48 hours |
| vit.K IV route | onset 1-2 hours control of hemorrhage evident in 3-6 hours |
| vit.K IV or >5mg po | leads to overcorrection and warfarin resistance lasting up to a week |
| never administer warfarin IM | never administer warfarin IM |
Created by:
lex86
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