EP244: Warfarin and Risks

Welcome to my podcast. I am Doctor Warrick Bishop, and I want to help you to live as well as possible for as long as possible. I’m a practising cardiologist, best-selling author, keynote speaker, and the creator of The Healthy Heart Network. I have over 20 years as a specialist cardiologist and a private practice of over 10,000 patients. Podcast Summary Introduction Dr. Warwick Bishop, a cardiologist, author, and CEO of the Healthy Heart Network, hosts this episode dedicated to educating listeners about warfarin and its dangerous drug interactions. With heart disease claiming one life every 20 minutes in Australia and affecting over 9 million people globally, Dr. Bishop emphasizes that most cases are preventable through proper health literacy and understanding medications like warfarin that require careful management. Key Takeaways Warfarin is a blood-thinning medication originally developed as a rat poison in the 1950s and approved for human use by the FDA in the mid-1950s, remaining a critical anticoagulant for decades. Warfarin is still essential for patients with mechanical heart valves, as newer anticoagulants (Xarelto, Eliquis, Pradaxa) have not yet been proven as safe or effective for this specific application. Warfarin works by blocking vitamin K1, which is necessary for the liver to synthesize clotting factors (2, 7, 9, and 10) in the body's coagulation cascade. The drug is metabolized through the liver's P450 system, and many medications including antifungals and antibiotics can interfere with this system, causing warfarin to accumulate dangerously in the body. Warfarin dosing is carefully monitored using the INR (International Normalised Ratio) test, which measures how long blood takes to clot; the target is typically 2.5, meaning blood clots 2.5 times slower than normal. Warfarin interactions can cause INR levels to spike dangerously to 6, 7, 8 or higher, creating risk of spontaneous internal bleeding in the brain, gastrointestinal system, or urinary system—a medical emergency. Patients on warfarin must always inform their doctors about any new medications and ask specifically if they interact with warfarin before taking them. Maintaining a current list of all medications and carrying it with you is essential for quality medical care and preventing dangerous drug interactions.