Warfarin Basics&Patient Education :Warfarin Basics&Patient Education 2009 Approx. time 30 min
Objectives :Objectives After completing this activity, the participant will be able to:
Explain:
Basic characteristics of warfarin’s effect
Laboratory monitoring for warfarin
Effects of diet on warfarin
Common adverse effects
Provide essential elements of warfarin patient education
What is it? :What is it? Generic name = warfarin sodium
Brand = Coumadin®
Branded Generic = Jantoven®
Effects uncovered by Midwest farmers, 1920s
Isolated from spoiled sweet clover, 1939
by the Wisconsin Alumni Research Foundation
Used as rat poison
Commercially for human treatment, 1955
What makes warfarin different? :What makes warfarin different? Highly variable response from patient to patient
No standard way to estimate the dose needed
Requires frequent blood tests (PT/INR)
HIGH RISK MEDICATION
Small difference between ineffective levels & toxic levels
Frequent dosing changes based on PT/INR
Numerous interactions
Dietary habits affect the response & dose
General Characteristics of Warfarin :General Characteristics of Warfarin Slows the normal clotting process
Vitamin K is needed to produce 4 clotting proteins
Warfarin blocks activity of vitamin K
Reduces the amount of clotting proteins
Technically, it does not “thin” the blood
Does not dissolve clots
Prevents extension of existing clots
Prevents formation of new clots, when used at the appropriate levels
General Characteristics of Warfarin :General Characteristics of Warfarin Effect builds slowly
1 week or more to see maximal effect
Long-lasting effects
Stop taking prior to surgical procedures
Up to 5 days are needed to achieveINR < 1.5
Vitamin K is the antidote for warfarin
Vitamin K and Warfarin: Opposites :Vitamin K and Warfarin: Opposites Vitamin K is needed in the blood’s normal clotting processes
Lowers INR by making more clotting factors
Warfarin blocks the action of vitamin K
Pushes INR higher
Blood will still clot, but at a slower rate
Slows down the formation of harmful clots
Blood Tests: How “Thin”? :Blood Tests: How “Thin”? Prothrombin Time (PT)
Measure of time for blood to coagulate (seconds)
International Normalized Ratio (INR)
A calculation using PT adjusts for lab-to-lab variability of testing reagents
The gold standard for evaluating warfarin’s effect on clotting
Blood Tests: How Often? :Blood Tests: How Often? Inpatients must have baseline INR before giving the first dose
INR on admission for those already taking warfarin chronically
INR measurements daily as inpatient
Exception for BHS patients on stable doses
Blood Tests: How Often? :Blood Tests: How Often? Outpatients
For new patients, 1 – 2 times weekly
When INRs are consistent & stable
Extend to weekly, or every other week
No less frequent than every 4 weeks for stable patients
Efficacy/Safety Relationship :Efficacy/Safety Relationship For persons not taking warfarin, normal INR range is 1.0 – 1.2
Very different when taking warfarin
INR too low (ex. 4.5)
Increased risk for major bleeding events
Slide 13:Hylek EM, et al. Ann Internal Med 1994; 120:897-902 Too Low Too High
Efficacy/Safety Relationship :Efficacy/Safety Relationship INR range depends upon indication
2.0 – 3.0
Stroke prevention in persons with AFib, AFlut
DVT/PE treatment
Hip or knee replacement
2.5 – 3.5
Some mechanical heart valves
Some hypercoagulable conditions (genetics), or people who have developed clots at lower INRs
Factors Affecting Warfarin Dose :Factors Affecting Warfarin Dose Age
Drug Interactions
Diet
Lifestyle / Habits
Adherence to Therapy
Age :Age Older patients typically need less warfarin
First doses no larger than 5mg for inpatients 75yo or older
Maximum first dose of 10mg for all younger inpatients
Other Medications w/ Warfarin :Other Medications w/ Warfarin MANY different medication interactions
Some medications will cause warfarin to accumulate in the bloodstream
Increased chances of bleeding
Some decrease warfarin’s effect
Antibiotics commonly interact with warfarin
Diet Considerations :Diet Considerations Certain foods, especially green leafy vegetables, have large amounts of vitamin K
Eating too much of these at one time may reverse the benefit of the warfarin
Important to note which foods are high in vit K
Some Foods High in Vitamin K :Some Foods High in Vitamin K Green leafy vegetables
Broccoli, brussels sprouts, cabbage, collard greens, endive, green scallion, kale, spinach, turnip greens, watercress
Salad Oils
canola, salad, and soybean oils
mayonnaise
Liver
Lifestyle / Habits :Lifestyle / Habits Alcohol use
Acute use (>2 drinks/day) increases INR
Exercise
Increased exercise may decrease INR
Smoking or Chewing Tobacco
Increased use may decrease INR (vit K in tobacco)
Smoking cessation may increase INR
Essential Patient Education :Essential Patient Education Recognize names (warfarin = Coumadin® = Jantoven®)
Reason to take it (indication)
Discuss INR and frequency of monitoring
How & when to take the doses
Signs and symptoms of bleeding; what to do
Counsel re: interactions, herbals, med. changes
Role of diet and vitamin K
Role of lifestyle choices (tobacco, alcohol)
Medic Alert bracelet/ID
Know the Names :Know the Names Warfarin is the generic name
Two brand names are Coumadin®, Jantoven®
Patients will never use more than one of these at the same time
Why Take Warfarin :Why Take Warfarin Atrial Fibrillation or Previous Stroke
Warfarin reduces the chances of having a stroke associated with AFib
Better than aspirin at preventing stroke caused by Atrial Fibrillation
Why Take Warfarin :Why Take Warfarin Deep Vein Thrombosis (DVT) and Pulmonary Embolus (PE)
Warfarin stops the clot from getting larger
Reduces the chance of repeat clot
The body’s normal processes break down the clot over time
Why Take Warfarin :Why Take Warfarin After Hip or Knee Replacement
Warfarin reduces chance of DVT
Abnormal Coagulation Profile
Genetic predisposition to form harmful clots
Warfarin can reduce the chances of forming harmful clots like DVT/PE
Unlike Any Other Medication :Unlike Any Other Medication Not the same dose for everyone
Small difference between benefit & risk
Too much = side effects, bleeding
Too little = ineffective, clots
Many different things affect the way your body responds to the warfarin
General Instructions :General Instructions Take warfarin every evening
If you miss a dose
If still dark outside, take it when you remember
If the sun is up the next morning, skip it
Record the date, inform provider at next INR
Tell all care providers you take warfarin
General Instructions :General Instructions Take only the doses prescribed
Doses may change based on the blood test results
Use a calendar, pillbox, or some other way to keep track
Have blood tests as instructed
INR Test :INR Test INR blood test is the only way to tell how well the medication is working
At first, these tests are frequent
At least once each month is recommended
INR is a measure of blood clotting
INR too high you may need less warfarin
Too low, you may need more warfarin
Target INR :Target INR Target Range is where
Therapeutic effect is maximized
Benefit of clot prevention
Side effects are minimized
Less chance of bleeding & bruising
Usual INR target is 2.0 – 3.0
May be 2.5 – 3.5 for heart valve replacements
Drug Interactions :Drug Interactions Changes to existing therapy should always be reported to AC provider
Starting a new drug
Stopping an old drug
Increase/decrease in dose
Herbals or alternative medicines
Antibiotics
Other Medication :Other Medication Medications to Avoid :
NSAIDs (Aleve, Advil, Ibuprofen, Naproxen)
Aspirin (unless prescribed by doctor)
Increase risk of stomach bleeding
Always check with pharmacist or doctor before starting a non-prescription drug
Adverse Effects :Adverse Effects Bleeding
Related to INR levels; can occur at any level
Bleeding risk increases when INR > 4.5
Antiplatelet agents increase bleeding risk
Aspirin, Plavix®, NSAIDs
Sites of bleeding
Gastrointestinal, Nose, Gums, Intracranial
Signs of Warfarin Excess :Report unusual bleeding
Blood in stool (black, tarry color)
Blood in urine (brown, red/pink color)
Excessive nose bleeds/bleeding gums
Persistent oozing from superficial injuries
Excessive menstrual bleeding
Unusual bruising (large areas) Signs of Warfarin Excess
Get Immediate Treatment! :Get Immediate Treatment! Red or dark brown urine
Red or black stool
Vomiting blood, or coffee ground material
Sudden severe headache
Lightheadedness, fainting
Severe abdominal or back pain
Notify Doctor :Notify Doctor Frequent or heavy nose bleeds
Unusual, excessive bruising
Prolonged bleeding of cuts
Bleeding gums
Diet Advice for Patients :Diet Advice for Patients Don’t change your diet when starting warfarin
Try to maintain consistency
Be aware of foods high in vitamin K
Limit portion size of high vitamin K foods
Consult your provider before making big changes to your diet
Diet and Warfarin :Diet and Warfarin Completely avoidingvitamin K containing foods isNOT recommended
Other Instructions :Other Instructions Avoid pregnancy
Avoid alcohol in excess
Get refills on time, don’t run out of warfarin
MedicAlert ID or carry medication list
If you smoke, tell your provider if you quit
Resources :Resources On Demand program on hospital TV
“Patient’s Guide to Warfarin”
Booklet ordered from Patient Education Dept
“The Warfarin Lifestyle”
Group education sessions
Monthly in York; call for Gettysburg sessions
For schedule, call 1-800-840-5905
Online
www.mybloodthinner.org
www.ahrq.gov/consumer/coumadin.pdf
1-800-COUMADIN
Summary :Summary Warfarin is a unique medication
Requires patient education for safe use
Use handouts in combination with verbal instructions
Properly educated patients should
Understand the need for INR testing
Recognize adverse effects
Know what to do
Slide 42:To obtain full credit, please complete the quiz associated with this activity.
Shawn Slenker, PharmD
WellSpan Anticoagulation Services
sslenker@wellspan.org