Many horses have flying insect allergies and other allergies as well as respiratory disease, such as equine asthma, that require steroids like prednisolone to control their symptoms.  However, many of these horses also have laminitis or founder or may be overweight, have equine metabolic syndrome or Cushing’s disease, making them susceptible to laminitis and founder. In these horses, steroids have been reported to increase the chance of laminitis and founder developing, and yet allergic conditions in many cases require their use. 

To determine the safety of using oral prednisolone in these horses, a British study was done over a 13-year period; 416 horses that received prednisolone were compared to 814 control horses that hadn’t.  The median age of the horses was 13 and no significant differences between breeds and sexes were noted.  The laminitis rate was calculated and there was no significant difference between prednisolone-treated and non-treated groups in overall incidence of laminitis.  There were 62 total cases of laminitis with an incidence of 3.5% of the horses not treated with prednisolone and 2.5% of those treated with prednisolone, but about 50% of the horses treated with prednisolone developed laminitis while on the drug.  Also, 50% of the horses that developed laminitis on the drug also have equine metabolic syndrome or Cushing’s disease.  So, it appears from the study that prednisolone did not increase the risk of laminitis.  However, I believe one should still be cautious using it in horses with equine metabolic syndrome or Cushing’s disease unless absolutely necessary and then understand there may be a risk with its use.