There are some drugs that seem to have been around forever. A perfect example is heparin, a traditional anticoagulant. Discovered by accident in 1915 by a second-year medical student at Johns Hopkins University, heparin was…
There are some drugs that seem to have been around forever.
A perfect example is heparin, a traditional anticoagulant. Discovered by accident in 1915 by a second-year medical student at Johns Hopkins University, heparin was not available on the market until the 1930s. It was originally administered intravenously. The first oral anticoagulant, warfarin, was approved by the Food and Drug Administration in 1954 and, in fact, prescribed to President Dwight D. Eisenhower in 1955. Heparin and coumarins, including warfarin, have been the mainstay of anticoagulant therapy for more than 60 years in the United States.
Ironically referred to as blood thinners, heparin and coumarins do not make your blood thinner but rather keep your blood from getting thicker. Often prescribed to treat some kinds of heart disease, they’re also used to prevent heart attacks and strokes.
While warfarin and heparin both block the production of cofactors, those proteins in your liver that aid in the clotting process, they each function differently. Warfarin has the unique role of reducing clotting in your blood circulation by preventing vitamin K from working correctly. Heparin prevents other cofactors, thrombin and fibrin, from working correctly by binding active clotting factors to promote anticoagulation. By interfering with the process, both warfarin and heparin ultimately help reduce blood clots from forming in your body.
Warfarin and the other drugs in this class of older drugs are not without challenges. Of primary importance, they inherently carry the risk of causing bleeding. Also, because these drugs are generally taken by seniors, who are often taking a host of other medications and may have cognitive decline, there may be a higher risk of medication “misadventure.”
Another challenge is related to time. Frequent blood testing is required to measure how quickly the blood clots and the concurrent risk for bleeding. This laboratory measurement, known as the international normalized ratio, is the best way to determine the effectiveness of an oral anticoagulant and ensure the correct dosage is being prescribed. Sometimes your INR has to be checked monthly or weekly to make sure your drug level is effective. And many patients find it challenging to take the medication at the same time each day, which is a highly recommended practice.
Finally, because warfarin is generic and produced by a multitude of companies, each product is not absorbed or metabolized in the same way. You can buy 5 milligrams of warfarin from company A, which is not the same as 5 mg from company B. The only way to circumvent the problem is for the physician to prescribe a branded form of warfarin to the patients.
More recently, a class of blood thinners was developed that would obviate the need for constant testing. The first group, which included Xarelto, Pradaxa and Eliquis, was introduced in 2010 and referred to as Novel Oral Anti Coagulants. What was novel about these agents is that they did not reduce the number of clotting factors but instead directly binded to clotting factors. The time benefit is extremely significant, as you don’t need to be lab-tested regularly. Another huge benefit is that you don’t need to avoid foods with vitamin K like green leafy vegetables, which would negate the positive effect of the drug.
Here’s the irony about the new classes of drugs. Very often, we still prescribe the old ones.
For some conditions, newer agents cannot be prescribed. Those with mechanical heart valves can’t be on these newer medications because proper dosing has not been established, and there may be a higher risk of clotting. Also, some insurance companies won’t pay for these newer drugs, so it becomes a financial decision.
Putting specific medical conditions and finances aside, there is a matter of pure preference. Some patients prefer to take warfarin since the newer agents, until recently, did not have a reversal agent. A reversal agent is a solution of cofactors and clotting chemicals that counteract the anticoagulant effect of these medications.
And warfarin is more easily reversed, though clinicians may not recognize the need for reversal soon enough to change the outcome.
In our fast-changing world, there are indications coming down the pike for the newer agents like peripheral vascular disease and acute myocardial infarction ( heart attack), which will likely be announced at the end of the year. New research published in the European Heart Journal suggests anticoagulants may not only prevent a stroke but reduce the occurrence of dementia in those diagnosed with atrial fibrillation.
While the traditional class of anticoagulant drugs may have a history of success behind them, from a clinical perspective, I prefer and generally prescribe the newer ones. The ease of use, predictability, lack of variability and lack of need to be near a lab provides better compliance and, ultimately, better results.