Field use of N-butylscopolammonium bromide to facilitate thorough ophthalmic examination in horses.
Authors: Palmero J, Hollingsworth S, Kass P, Moore S, Pusterla N
Journal: Veterinary journal (London, England : 1997)
Summary
N-butylscopolammonium bromide (NBB), an anticholinergic agent traditionally used in equine colic treatment, was evaluated by Palmero and colleagues as a potential mydriatic for field ophthalmic work, addressing the practical challenge of achieving adequate pupil dilation without access to standard topical agents. Their crossover trial involved six horses receiving four randomised treatments (saline control, topical tropicamide, topical NBB, and intravenous NBB) with measurements of pupil diameter, mydriasis quality, and pupillary light reflexes recorded throughout. Whilst tropicamide performed reliably, producing mydriasis in all horses, NBB showed limited efficacy—topical application induced mydriasis in only one horse, and intravenous NBB allowed thorough fundic examination in just two animals, with inconsistent results ranging from delayed light reflexes to no apparent effect. Although NBB cannot replace tropicamide as a standard mydriatic agent, the variable response to intravenous administration warrants consideration in emergency field situations where conventional agents are unavailable, though practitioners should not rely on this approach for routine ophthalmic screening or when standard medications are accessible.
Read the full abstract on PubMed
Practical Takeaways
- •Tropicamide remains the superior choice for reliable mydriasis in field ophthalmic examinations of horses; neither topical nor IV NBB provided consistent results
- •If NBB is considered, intravenous administration was more likely to produce some mydriatic effect than topical application, though success rates were low
- •NBB cannot be recommended as a reliable alternative to tropicamide for routine equine eye examinations in field settings
Key Findings
- •Tropicamide induced mydriasis in all 6 horses, enabling complete fundic examination
- •Topical N-butylscopolammonium bromide (NBB) induced mydriasis in only 1 of 6 horses
- •Intravenous NBB enabled thorough fundic examination in 2 of 6 horses, delayed pupillary light reflexes without adequate mydriasis in 2 horses, and had no effect in 2 horses
- •NBB showed inconsistent mydriatic efficacy compared to tropicamide as a field mydriatic agent in horses