Ever since there has been horse racing there has been debate about what is fair to the horses as well as what is fair to the bettors. For the past few years a debate about lasix has come back to light. This debate features the pro-lasix debate that lasix help horses by preventing exercise-induced pulmonary hemorrhage while people who are against lasix claim that it weakens the thoroughbred bred and it gives horses on lasix an unfair weight advantage. Now you’re probably wondering what this debate is doing on a science blog, the answer is that of the science behind the debate. Lasix is a diuretic, as most of you probably remember form studying the kidney a diuretic makes you urinate more and flush fluids for your body while and anti-diuretic (like ADH) leads to water reabsorbtion and retention. People who are against lasix feel that because lasix makes horses urinate it gives them an unfair weight advantage (at times up to twenty seven pounds). In horse racing any amount of weight loss is a huge advantage as horses in “handicap races” are usually spread over a 7lb weight range to carry and in most of the larger races all horses carry an equal weight so as not to give anyone to large of an advantage. There is also the idea that horses have multiple causes for bleeding as there are exercise-induced pulmonary hemorrhage which is when the blood vessels in a horses lung rupture from very hard exercise, but there is also Patent pulmonary hemorrhage which is bleeding in the lungs due to an allergy, illness or hypertension and it has not been proven that lasix helps any of these conditions. This side also argues that lasix allows horses that bleed to run better, and therefore weakens the thoroughbred breed because it allows horses who are prone to bleeding to pass on this trait. Though the anti-lasix side has a lot of logic to back it up it is the pro-lasix side of the debate that has science behind them. The pro-lasix side of the argument is greatly based of a study from South Africa. This study proved for the first time that lasix is effective in treating exercise-induced pulmonary hemorrhage. This is caused by a horses intestines swinging when a horse is running and hitting the lungs in an offbeat. If the intestines swing into the lungs when the diaphragm is expanded then the lungs are compressed and capillaries and blood vessels hemorrhage leading the bleeding in the lungs. This study followed 167 horses for two races, against the similar company and in similar conditions. These horses received lasix before one race and placebo before another. The results showed that horses who got lasix were 3 to 11 times less likely to bleed. This study also proved that if a horse bled due to EIPH the first time and then received lasix they were 2/3 less likely to bleed in the next race showing that lasix can help horses that already have a history of bleeding. The lasix debate is a complex one but now there is science to back up the use of lasix in horses with EIPH. As the US looks toward banning race day medications (lasix) to become more competitive in the world of racing they will now be forced to question whether race day medication is a necessity. So now I ask you to do the same after reading both sides of the argument what side are you on?