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Evaluation of the systemic effects of topical application of 1% atropine sulfate ophthalmic solution in healthy horses

2017-12-01 13:57:16

Journal of the American Veterinary Medical Association

December 1, 2017, Vol. 251, No. 11, Pages 1324-1330

https://doi.org/10.2460/javma.251.11.1324



Rita F. Wehrman DVM, MS; Anne J. Gemensky-Metzler DVM, MS; Ashley E. Zibura DVM; Amelia B. Nyhart DVM; Heather L. Chandler PhD



Abstract


Objective
To determine the safety of topical administration of 1% atropine ophthalmic solution in healthy horses by objectively measuring gastrointestinal transit time.



Design
Randomized, masked, controlled crossover study.



Animals
6 adult geldings.



Procedures
Horses were randomly assigned (3/group) to first receive topical treatment of the left eye with 1% atropine or artificial tears solution; the right eye was left untreated. After 24 hours of treatment every 6 hours, 200 nontoxic beads were administered to each horse via nasogastric intubation and treatment frequency was decreased to every 12 hours for 4 more days. Pupillary light reflexes (PLRs), mydriasis, heart rate, fecal bead passage, abdominal girth measurements, auscultable gut sounds, fecal weight, and clinical signs of abdominal pain were monitored. Following a 4-week washout period, horses received the opposite treatment in the left eye and measurements were repeated. Serum atropine concentration (reflecting systemic absorption) was measured with an ELISA at various points after initial atropine administration.



Results
No horse had subjective or objective evidence of colic or ileus at any monitoring point. Complete mydriasis of the left eye with absence of the PLR was identified in 5 horses within 6 hours and in all 6 horses within 12 hours after initial atropine administration. One horse had mydriasis with an absent PLR in the untreated eye by day 5 of atropine treatment. At no point was atropine detected in serum samples of any horse.





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