An observational study has found that 2-year-olds racing without race-day furosemide at the 2013 Breeders’ Cup World Championships at Santa Anita Park had fewer and less severe instances of exercise-induced pulmonary hemorrhage (EIPH) than juveniles who raced with the diuretic that same weekend at Santa Anita.

While the study was observational as opposed to scientific—and the sample size small—researchers observed a statistically significant higher percentage of EIPH frequency, and severity, in horses treated with furosemide Nov. 1 at Santa Anita compared with those who raced without it that weekend at the track.

Furosemide (commonly called Salix or Lasix) is the only race-day medication permitted in North American racing and it’s used to treat EIPH, which at its most severe grade can include bleeding through the nostrils. Breeders’ Cup has prohibited race-day Salix use in juvenile races in the two most recent World Championships.

This year Breeders’ Cup followed up that Salix policy with endoscopic exams for EIPH of juveniles whose connections opted to participate in the voluntary study, which also looked at horses volunteered from a pair of stakes races for juvenile California-breds conducted that same weekend