A study examining catastrophic injuries over a 10&#45;year period at four South American racetracks has shown a significant increased risk of fatality for horses that have been administered phenylbutazone, an anti&#45;inflammatory drug that is commonly used in treating racehorses in the United States.The results of the study, which were first reported in the Blood&#45;Horse, could bolster efforts by some racing organizations to further tighten rules governing the administration of Bute, as the drug is commonly called. Bute is currently prohibited to be administered within 24 hours of a race in all states, and many states have adopted tighter rules extending that prohibition to 48 hours. California recently put in place rules that effectively ban the use of the drug within seven days of a race.The study, which examined 500,000 racehorse starts at the four South American tracks from 2006 to 2015, found numerous risk factors contributing to racehorse injuries, but the correlation with phenylbutazone use &ldquo;is the first time such association is demonstrated,&rdquo; according to the study, which was conducted by Teresita Zambruno, a graduate student of Tim Parkin, an epidemiologist at the University of Glasgow who oversees the analysis of a U.S. database on racehorse injuries.Zambruno wrote in the study that the risk associated with phenylbutazone use &ldquo;is probably because those horses need anti&#45;inflammatories or analgesics to have a good performance or make it to the race. This could be due to clinical or subclinical pre&#45;existing injuries or pain. Thus phenylbutazone administration may allow horses to continue training and racing, accumulating damage to their musculoskeletal structures and increasing the odds of fatalities.&rdquo;The Blood&#45;Horse said in its report that Parkin would argue in an upcoming essay to be published in the company&rsquo;s magazine that use of phenylbutazone in the United States should be migrated to a &ldquo;zero&#45;tolerance&rdquo; policy due to the study&rsquo;s results. The Blood&#45;Horse is owned by The Jockey Club, which has been aggressively pushing for tighter medication rules in racing for many years.The Blood&#45;Horse said in its report that Parkin would say in the essay that &ldquo;horses racing with Bute in their systems are 50 percent more likely to sustain a fatal or nonfatal musculoskeletal injury that those racing without a recent administration of the non&#45;steroidal anti&#45;inflammatory.&rdquo;The term &ldquo;zero tolerance&rdquo; is tricky to define due to the limits of laboratories when conducting tests on post&#45;race samples. However, a zero&#45;tolerance policy would almost certainly lead to much tighter rules on phenylbutazone regulation in the U.S., somewhere along the lines of the current California rules, which were implemented this year in response to a spate of fatalities at Santa Anita Park.Mary Scollay, the executive director of the Racing Medication and Testing Consortium, said on Friday that guidelines on phenylbutazone use published by the British Horseracing Authority could serve as a standard for a &ldquo;zero&#45;tolerance&rdquo; policy, though she cautioned that differences in lab&#45;detection abilities made the issue an &rdquo;unanswerable question.&rdquo; The BHA currently prohibits phenylbutazone within seven days of a race, and prohibits the use of two other anti&#45;inflammatory medications, banamine and ketoprofen, within six days and four days of a race, respectively.The U.S. racing industry has been struggling to lower its fatality rate over the past 10 years, despite numerous analyses of risk factors associated with catastrophic injuries and the 2009 creation of perhaps the world&rsquo;s most comprehensive database of racehorse injuries.The issue of medication use in U.S. racing is a controversial topic in which powerful constituencies on either side of the debate have found little room for compromise due to inflamed passions over the raceday use of furosemide, a diuretic that is legal to use on raceday to treat bleeding in the lungs in all North American racing jurisdictions but illegal to use on raceday in most other foreign racing jurisdictions. (The study conducted by Zambruno included tracks in South America where raceday use of Lasix is legal, and found no risk factors associated with the drug.)However, the U.S. racing industry has begun to increasingly focus on the use of anti&#45;inflammatory drugs such as Bute and corticosteroids as risk factors, and many jurisdictions are attempting to put additional restrictions on the medications. Those efforts have included the extension of the prohibition on Bute and other non&#45;steroidal anti&#45;inflammatories to 48 hours, and the extension on the prohibition of the intra&#45;articular use of corticosteroids from seven days to 14 days.The paper by Zambruno is further bolstered by a recent study conducted by Heather Knych, a top equine pharmacology researcher at the University of California. Earlier this year, Knych published a study showing that anti&#45;inflammatory markers persisted in a horse&rsquo;s system &ldquo;for a prolonged period of time&rdquo; following administration of the drug, well past the 48&#45;hour prohibition being sought in most jurisdictions. Use of anti&#45;inflammatories can complicate the work of regulatory veterinarians conducting pre&#45;race examinations of horses by masking pain in areas that may be injured. Pre&#45;existing injuries are one of the leading causes of fatalities, and many of those pre&#45;existing injuries can be hard to identify without sophisticated and costly medical scans to identify micro&#45;fractures in the bone.