Case Control and Historical Cohort Study of Diarrhea Associated With Administration of Trimethoprim‐Potentiated Sulphonamides to Horses and Ponies

Abstract

Trimethoprim-potentiated sulphonamides (TPS) are among the most frequently administered antimicrobials in equine medicine. Anecdotally, TPS has been implicated as a cause of mild t o moderate diarrhea in horses. The purpose of this study was t o document the prevalence of diarrhea in horses receiving TPS, t o characterize the severity of the diarrhea, and t o identify any other factors associated with the development of diarrhea. A 2-part study was designed t o identify the prevalence of diarrhea associated with TPS in our clinic population. Part I was a case-control retrospective study of 135 records over a 10.5-year period from January 1, 19801, through June 30, 1990. Part II was a historical cohort study of 784 records over a 37-month period from July 1, 1990 through July 31, 1993. There was no significant difference in the occurrence of diarrhea associated with TPS therapy dverse effects associated with antimicrobial administra-A tion occasionally occur. Several antibiotics have been documented to cause diarrhea in horses; the most common ones are o~ytetracycline,'.~ lincomycin,' erythromycin, and peni~illin.~.' Trimethoprim-potentiated sulphonamides (TPS) are frequently used in horses, where they have been anecdotally implicated in cases of mild to moderate diarrhea.*-" However, there have been no controlled studies evaluating the incidence of diarrhea after TPS administration. The purpose of this 2-part study utilizing 2 epidemiological methods was to document the prevalence of diarrhea after TPS in horses, to characterize the severity of the diarrhea, and to identify any other factors associated with the development of diarrhea. Materials and MethodsThe study was conducted in 2 parts from horses admitted to the University of Missouri Veterinary Teaching Hospital. The first part was a case-control retrospective study over a 10.5-year period from January I , 1980 through June 30, 1990, and the second part was a historical cohort study over a 37-non nth period from July I , 1990 through July 3 I , 1993. In part I, horses with a diagnosis of diarrhea were identified. Age-matched controls were then selected, and the records were evaluated for several parameters, including the administration of TPS, penicillin, and other antibiotics. In part 11, horses that had been treated with TPS were identified by a search of our computer database, as well as a review of the record. Age-matched controls were then selected, and the records were evaluated for several parameters, including the development of diarrhea, and the administration of penicillin and other antibiotics. Part IRecords were selected for inclusion in part I of the study if the 1. They did not have diarrhea or a complaint associated with the 2. They stayed at least 2 nights in the hospital. 3. They were over 2 weeks of age at the time of admission Cases of diarrhea were identified from a review of our teaching hospital records database. Additionally,. horses with diarrhea were evaluated for final outcome, duration of diarrhea, and hematologic variables b...

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