I believe we can prevent heart attack. We can put in place strategies to reduce risk. We can literally plan to change your future. Welcome. My name is Dr. Oreck Bishop. I'm a cardiologist. I'm an author and a keynote speaker. Together with that, I'm CEO of the Healthy Heart Network and I'm all about trying to help people live as well as possible for as long as possible. You probably know, heart disease is huge in Australia. Every 20 minutes someone suffers a heart attack and we know that over 20 people per day die from heart disease. This is on the backdrop of over 9 million people globally being impacted by this condition. Truthfully, most of these could probably have been avoided if only we knew what to do. This podcast is all about helping you understand better where blood pressure, weight, cholesterol and all the other bits and pieces around there can help together with general health literacy for general better health. I am on a mission to impact not just heart health but general health on a global scale. If you enjoy this podcast, I would be honoured for a five-star review and... You can share it with your family and friends. Who knows? It may well save someone you love. Hi, my name's Dr. Warwick Bishop, and welcome to my podcast and videocast station, and thank you for joining me. Today I'd like to talk about warfarin and warfarin interactions. Well, some of you may be on warfarin if you have a heart valve, for example. Some of you may never have heard of warfarin, so let me tell you a little bit about what it is. Warfarin's a drug that we use to thin the blood. Warfarin actually came to commercial notoriety around about 1950 when it was first used as a rat poison. So you may well have come across warfarin or Coumadin, which we've used now for a good number of years. poisoning rats. The rats would eat the warfarin, have internal bleeding from overdosing, and that would lead to their demise and obviously control the rodent problem. It wasn't until about five years after mid-1950s that warfarin was cleared by the FDA to be used in humans. And we've used it up until relatively recently as the mainstay for blood thinning. And we use blood thinning a lot in cardiology. If someone has a clot in their leg, we thin the blood. If that clot in the leg, which is called a DVT, deep vein thrombosis, moves to the lungs, which is called a pulmonary embolus, We would give anticoagulation. We've realized over the last decade or two that atrial fibrillation can lead to clot in the heart. And so we use blood thinners for that as well. And up until recently, it's been warfarin. Importantly, if people get a new heart valve so that blood doesn't stick and clot on that new heart valve, we also give blood thinners, in particular warfarin. In the last five to ten years, we've seen a broad uptake of agents, which are a new iteration on blood thinners and work a bit differently to warfarin. We think of warfarin as a vitamin K blocking agent. And these new agents are novel. oral anticoagulants or non-vitamin K oral anticoagulants. And these non-vitamin K oral anticoagulants include drugs which go by the names of Xeralto, Eliquis, Pradaxa. And we use these a lot in clinical practice now where we used to use warfarin. particularly for atrial fibrillation, clots in the legs, clots in the lungs. But we still need to use warfarin for people with heart valves because we're yet to demonstrate that these new agents are as safe or as effective as warfarin in the setting of a mechanical heart valve in an individual who's had valve replacement. So there will be people still on warfarin out there. As I mentioned, warfarin works through vitamin K. And it's actually vitamin K1, not vitamin K2. Vitamin K2 tends to be more involved with the bones. Vitamin K1 is involved in the liver synthesis of the proteins, which are part of the coagulation cascade. And these are proteins that trigger off a response. in the setting of a potential threat to blood loss and drive formation of a clot. There's a number of factors involved when it comes to vitamin K1. Dependent factors, they're factors 2, 7, 9 and 10. So all of these factors get impacted through warfarin therapy. Well, one of the reasons I thought I'd share... a podcast about warfarin, is that it is not uncommon for warfarin to be interfered with or have interactions with by other drugs. And that's through a clearance system in the liver called the P450 system. And that system, if you like... makes sure that the warfarin is metabolized and removed from the body so it doesn't accumulate. Unfortunately, there are a number of drugs out there that can alter the P450 system, slowing it down, meaning that warfarin can accumulate. And therefore, if warfarin accumulates, the blood can be thinner than it should be because there's more warfarin around. Warfarin is generally dose-adjusted on a regular basis. Patients will have blood tests once a week initially to make sure that the warfarin level is right for that individual. The dose will be adjusted up or down depending on how thin the blood is measured on a special test called an INR, which stands for International Normalised Ratio and is really... a comparison to how quickly normal blood would clot. We normally aim for an INR of about 2.5, which means that blood from a patient appropriately treated on warfarin, aiming at an INR of 2.5, would have that blood clot at a rate of 2.5 times longer than somebody... who was normal and didn't have any warfarin on board at all. So it's a ratio and a comparator. Well, if we inadvertently give someone who's got warfarin a medication that can interact with that P450 system, and importantly things like antifungals and antibiotics can do this, then the... Warfarin levels can build up, and the INR can jump. And once it jumps, it can jump up to dangerous levels, levels of 6, 7, 8, or even above. And at these levels, there is a chance for spontaneous internal bleeding, which can lead to blood in the brain, blood in the gastrointestinal system, blood in the urinary system. A terrible situation. Very much a medical emergency which needs immediate treatment. Why am I mentioning this? Well, if you happen to be on warfarin, I hope you're fully aware that if you are being prescribed any new medication whatsoever, that you ask, politely, if this drug is compatible with or if it interacts with warfarin. if you like, the standout example of a medication that can be significantly impacted by other medications. But almost anything you're on, it is well worth asking your doctor, I just want to check, does this drug, this new drug, go okay with the drugs I'm already on? So that's warfarin and warfarin interactions, but really it's a reminder that any time You're looking at a drug change. You really need to be making sure that you're aware of potential interactions, side effects and the consequences. Very important stuff. Also a reminder that it's a good idea to always carry a list of your medications with you. In fact, I do ask all my patients to do exactly that as it can be a real plus to providing good. quality medical care. So know exactly what you're on. Well, look, I hope you found that interesting and informative. If you are listening to my podcasts regularly on something like Spotify, I'd love you to review them and give them a few stars because then other people may be aware and might be able to share that information as well. Till next time, I'm going to wish you the very best. I hope you live as well as possible for as long as possible. Take care. And bye for now. a free risk check at www.virtualheartcheck.com.au
