Effects of trimethoprim-sulfadiazine on tear production and the fluctuations of Schirmer tear test values in horses.

The study examines the impact of the antibiotic trimethoprim-sulfadiazine on tear production in horses and investigates the normal changes in Schirmer tear test (STT) measurements. The research shows that this medication doesn’t reduce tear production and normal fluctuations in the STT are common in horses.

Overview of the study

• Conducted as a blinded, placebo-controlled, randomized clinical trial, this study aimed to understand how trimethoprim-sulfadiazine, an antibiotic, influences tear production in horses.
• The study also tracked regular alterations in Schirmer tear test (STT) values in these animals, a common test for measuring tear production.
• 15 horses were part of this research over an 8-week period. They were divided into two groups – a treatment group of eight horses that were orally administered 30 mg/kg trimethoprim-sulfadiazine daily, and a control group of seven horses that received a placebo (flour) at the same frequency.
• All participating horses were kept outdoors for the duration of the study, with tear test values measured at the 0, 2, 4, 6, 8-week marks, and an additional measurement taken 4 weeks after the treatment was discontinued.

Findings of the research

• The study found no significant differences in tear production between the horses that received trimethoprim-sulfadiazine and the ones that took the placebo, suggesting that this antibiotic does not influence tear production levels in horses.
• There were identifiable fluctuations in the STT measurements over time. These are understood to be natural variations, potentially as a result of individual and environmental factors.
• These findings imply that any changes noted in a horse’s STT values could be due to regular, individual or environmental variations rather than a side effect of taking trimethoprim-sulfadiazine.