Warfarin

Question 1

MOA

Answer 1

• Block synthesis of Vit-K dependent clotting factors in the liver
• Vit K is required to syn factors 2, 7, 9, 10

Question 2

OSA

Answer 2

Depend on the Vit K dependence factors (2, 7, 9, and 10)

• VII: 6 hours
• IX: 24 hours
• X: 40 hours
• II: 60 hours

Question 3

Indications

Answer 3

• A. Fib
• PE/DVT
• Thromboembolic complication associated with a.fib

=> should not taken w/ ASA or NSAIDS

Question 4

What is the recommend start dose of warfarin base on ACCP 2012 guideline?

Answer 4

• 10 mg PO QD x 2 days for health adult
• Initiate warfarin on the same day as heparin or LMWH. Overlap anticoag for few days until IRN > 2 for 2 consecutive days => then d/c Heparin or LMWH

Question 5

Dosage forms of Coumadin

Answer 5

Please Let Greg Brown Brings Peaches To Your Wedding

• 1 mg = Pink
• 2 mg = Lavender
• 2.5 mg = Green
• 3mg = Brown/Tan
• 4 mg = Blue
• 5 mg = Peach
• 6 mg = Teal or Blue- green
• 7.5 mg = Yellow
• 10 mg = White

Question 6

ADEs

Answer 6

• Hemorrage: gingival bleeding, blood under skin, blood in urine, black stool, nosebleed, cough up blood, vomit blood, hemorrhagic stroke
• GI: N/V/D
• Hemorrhagic skin necrosis

Question 7

DDI

• Foods:
• Drug incr bleeding
• Drug decr bleeding

Answer 7

Foods:
- Green leafy vegetables: asparagus, cabbage, cauliflower, turnip greens => contain Vit-K = coagulation

Drug incr bleeding

• Glucocorticosteroids
• EtOH
• Salicylates

Drug decr bleeding
- Rifampin, COC, phenytoin, Estrogen => ROPE

Question 8

Drugs that increase INR

Answer 8

• 3A4 inhibitors: macrolides, protease inhibitors, azole antifungals, grapefruit juice (limit to 3 glasses QD)
• TMP/SMX (Bactrim/Septra), metronidazole (flagyl)
• Garlic, ginger, ginko (genseng decreases INR)

Question 9

Warfarin & NSAIDs

Answer 9

• Not rec => incr risk of GI bleeding
• NSAID: incr gastric irritation & erosion the protective lining of stomach => cause GI bleed. Also decr cohesive of platelets in clotting formulation
• If need anti-pyretic => use APAP
• If have to use w/ NSAID => monitor INR QW

Question 10

Warfarin & Bactrim

Answer 10

• Increase risk of bleeding => increase INR
• Avoid if possible, if have to use it, then decr warfarin by 50% while on and after a week d/c of bactrim.
• Monitor INR QW

Question 11

Warfarin & Quinolone

Answer 11

• Incr effects of warfarin => ACCP rec not use together if possible
• MOA: Reduction of intestinal flora responsible for Vit K production & decr the metabolism & clearance of warfarin
• If use together, monitor INR every other day

Question 12

Contraindications

Answer 12

• Preg Cat X: Fetal Warfarin Syndrome = chondrodysplasia punctata & CNS abnormalities
• Hypersensitivity
• Easy bleeders like alcoholics

Question 13

Full anticoag takes how many days

Answer 13

5-10 days

Question 14

How often we check IRN once it has been stable?

Answer 14

Check 4-12 weeks

- Check 12W in reliable pts w/ stable INRs & no recent change in dose

Question 15

PK

Answer 15

• Rapidly and completely absorbed

- Protein binding 99%

Question 16

Reverse INR

• When:
• INR > 10 but no bleeding:
• Serious bleeding, regardless of INR
• INR b/w 4.5-10 w/ high bleeding risk:

Answer 16

• When: INR > 10 or if pt has been bleeding

INR > 10 but no bleeding:
- PO Vit K 2.5-5 mg & hold warfarin

Serious bleeding, regardless of INR

• Slow IV infusion of Vit K 5-10 mg PLUS 4 factor PCC (prothrombin complex concentrate w/ F 2, 7, 9, 10) or give FFP
• 4 Factors: is quicker & preferred

INR b/w 4.5-10 w/ high bleeding risk:
- 1-2.5 mg PO Vit K

Question 17

Warfarin Pt counseling

Answer 17

• Keep eating habits the same
• Keep a consistent diet of Vit K and E
• Keep appointment for blood testing
• Watch out for interactions with OTC and Rx drugs
• If you forget a dose, take it ASA on the same day. Do not double dose
• Do not take warfarin if you are pregnant or will become
• Watch for any signs of bleeding: dark brown urine, red or tarry black stool, bruising, prolonged bleeding from cuts or gums, nosebleeds, inc menstrual flow.