Patient discussions
Patients benefit from education concerning both their disease and their therapy. In particular, anticoagulants confer a risk for bleeding, and educating patients on the signs and symptoms of bleeding, avoiding concomitant drugs that increase bleeding risk, and being judicious in choice of activities with risk for injury is perceived by patients to be beneficial.[199][264] As with all medical therapy, emphasizing the importance of compliance to optimize outcomes is beneficial.
Warfarin
Patients must be counseled carefully about the proper use of warfarin and the need for regular follow-up and monitoring of their international normalized ratio (INR). Patients must understand the following:
Warfarin makes the blood more difficult to clot and therefore carries a risk of bleeding.
The effect of the drug is measured with a blood-clotting test called the INR.
Warfarin dose frequently changes over time, and dosing that varies with the day of the week is very common (e.g., 4 mg on Monday, Wednesday, Friday, and Sunday; 5 mg on Tuesday, Thursday, and Saturday).
Dosing is typically referred to in weekly dosing amounts given the day-to-day fluctuations in dose.
The desired or target INR values are generally between 2 and 3.
Many drugs interact with warfarin, so the physician/healthcare provider who oversees the warfarin treatment must be notified whenever a new medicine (e.g., prescription or over-the-counter medicine, supplement, or herbal therapy) is started for the first time, or when a current drug is stopped or the dose is adjusted. Nonsteroidal anti-inflammatory drugs (NSAIDs) should be avoided or used with extreme caution under physician supervision.
Even when drugs do not impact warfarin or alter INR levels, they may still increase the risk of bleeding through pharmacodynamic interactions (NSAIDs, selective serotonin-reuptake inhibitors).
Diet changes can affect the INR, especially the intake of foods with high amounts of vitamin K (e.g., spinach, broccoli); eating any amount of vegetables or food high in vitamin K is acceptable, so long as the intake is consistent from week to week. Alcohol should be consumed with caution and excess alcohol consumption should be avoided in all patients taking anticoagulants. Grapefruit juice should be avoided.
Activities that carry a high risk of trauma or serious bleeding should be avoided, or if this is not possible, additional safety precautions should be taken.
The INR must be checked (monitored) frequently, with blood tests, often once or twice weekly until the stable dose is reached, then on an extended interval (4-12 weeks) thereafter.
Patients should be instructed on how to handle a missed dose (the approach may vary according to the warfarin manager).
Patients must be very clear about the daily dose of warfarin and the colors of their different warfarin tablets.
A pill organizer can help.
Although direct oral anticoagulants (DOACs) do not require coagulation assay laboratory monitoring and drug-drug interactions are minimized when compared with warfarin, there are still some drugs that interact with DOACs and can lead to either increased risk of bleeding or increased risk of thrombosis (e.g., primidone, amiodarone, diltiazem, verapamil, rifampin, phenytoin, phenobarbital, NSAIDs).[199][200] Interactions are most commonly mediated via cytochrome P450 enzyme (CYP450) and/or the transporter permeability glycoprotein (P-gp).[200]
Patients should be taught about the range of signs and symptoms of bleeding and recurrent thrombosis in order to be adequately prepared to make a decision about seeking immediate medical attention or not.
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