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26 Cards in this Set
- Front
- Back
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Start people at 5-10mg of warfarin daily unless... (7)
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1)elderly (b/c have decr CL)
2)debilitated 3)malnourished 4)CHF 5)liver disease (impaired factor synthesis) 6)recent surgery 7)on meds that incr warfarin sensitivity |
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When to get first INR
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after 2-3 doses then adjust dose based on INR
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What to do if INR over goal BUT under 5.0 (w/ no sig bleeds) (4)
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1)lower dose or omit dose
2)monitor more freq 3)resume tx @ adjusted dose when therapeutic 4)if minimally high or due to transient facter then no dose decr may be reqd |
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INR over/at 5.0 but under 9.0 (no sig bleed) (7)
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1)omit next 1-2 doses
2)more monitoring 3)resume tx @ adjusted dose when therapeutic OR 1)omit 1 dose and give 1-2.5mg po VitK 2)particularly if at incr risk of bleed OR 1)give 5mg or more po VitK b/c pt needs urgent surgery 2)INR should decr in 24h and if it doesn't can give 1-2mg po VitK extra |
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INR over/at 9.0 (no sig bleed) (5)
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1)hold warfarin and give 2.5-5mg po VitK
2)INR should decr in 24-48h 3)monitor more freq 4)admin more VitK if necessary 5)resume tx @ adjusted dose when INR therapeutic |
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Sig bleed and incr INR (regardless of how high INR is) (3)
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1)hold warfarin
2)give 10mg po VitK slow IV with FFP, prothrombin complex concentrate OR recombinant factor 7a 3)repeat VitK admin q12h if INR is persistently high |
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If incr INR w/o bleed, how to give VitK
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po not sq/iv
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If long term variable INR w/ NO known cause.... (2)
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can try qd VitK @ 100-200mcg w/ close monitoring
initial dose adjustment to counter initial lowering of INR |
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Antiphospholipid syndrome effect on INR goal
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can incr goal to 2.5-3.5 if get recurrent thromboembolic events w/ therapeutic INR of 2.0-3.0
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Effect of large VitK doses
S-warfarin metabolized by... R-warfarin metabolized by... |
can cause warfarin resistance for 1wk+
2C9 (2-4x more potent than R) 1A2 and 3A4 |
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Drugs inhibiting CL of...
a)S-warfarin b)R-warfarin c)S&R warfarin |
a)flagyl, bactrim
b)omeprazole, cimetidine c)amiodarone |
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Decr INR by incr liver enzymes by...(4)
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1)barbiturates
2)rifampin 3)tegretol 4)azathioprine |
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Long/short term effects of EtOH
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1)long term decr INR (due to incr CL)
2)short term incr INR |
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2nd/3rd gen cephalosporins effect on warfarin
Thyroxine effect on warfarin Salicylates and APAP effect on warfarin along w/... (2) |
1)cephalosporins augment warfarin (inhibiting conversion of VitK)
2)Thyroxine augments warfarin (incr metabolism of coagulation factors) 3)salicylates over 1.5g/d and APAP can augment 3)Erythromycin and anabolic steroids can augment too |
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Sulfa and broad spectrum abx effect on warfarin
____ incr risk of bleeds by decr platelets (3) |
can augment warfarin in pts deficient in VitK by decr gut flora production of VitK and aggravating VitK deficiency
1)ASA (even small doses) 2)NSAIDs 3)high dose PCN |
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A.fib and INR ranges (3)
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1)prevent stroke and incr survival in A.fib
2)more effective than warfarin and ASA 3)low intensity (1.5-2.5) and ASA no better than ASA |
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Warfarin LD?
When using warfarin and heparin How often to monitor |
NEVER (consists of doses over 10mg)
after 4-5 days of warfarin and heparin, can dc heparin if INR therapeutic 2 days in a row NEVER more than 4wks |
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How to adjust doses (4)
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a)5-20% based on weekly dose
b)INR b/w 4-10, hold for 1 day or more b)If minimally elevate just monitor more frequently (absolute risk of bleed low even if high INR) c)INR 6-10, if you hold 2 doses INR under 4.0 in 67% of pts, under 2.0 in 12% of pts |
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Dosing of rapid reversal agents (2)
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1)500IU of prothrombin complex concenrate is optimal for rapid reversal of INR under 5.0, but need more for INR over that
2)Factor 7a dose is 10mcg/kg up to 400mcg/kg cumulative dose |
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Most consistent predictors of major bleed (5)
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1)hx of bleed (especially GI)*****
2)hx of stroke 3)renal insufficiency 4)anemia 5)HTN |
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When you see major ADRs of warfarin (2)
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1)skin necrosis and gangrene on days 3-8 of tx (possibly due to protein C deficiency)
2)handle by restarting @ low dose (2mg) to avoid abrupt falls in protein C and adjust over 1 or more weeks |
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Effects of VitC and VitE on warfarin
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VitC)limit to 1g/d b/c VitC may block warfarin's effect (get decr INR)
VitE)doses over 800U/d may incr INR (along w/ fish oil and garlic) |
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Conditions w/ INR goal of 2.5-3.5 (3)
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phospholipid syndrome
mechanical prosthetic valve (except bileaflet mechanical valve in aortic position, left atrium normal size, NSR, normal EF) Acute MI |
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Follow up algorithm (4)
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If in goal can follow up in 5-10 days if you get 1 therapeutic INR
if 2 straight INR, can do 2wk follow up if 3 straight INR, can do 3wk follow up if 4 straight INR, can do 4wk follow up |
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Longest half-life of factors that warfarin inhibits
After first starting warfarin you may see |
2- 60 hours
hypercoagulable- b/c blocks protein C/S in first 36h |
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Other clotting factor half-lives
Protein C/S half-lives |
7- 8 hours
9- 24 hours 10- 39 hours 2- 72 hours C- 14 hours S- 42 hours get depeleted faster than clotting factors |
