Cardiovascular effects of N‐butylscopolammonium bromide and xylazine in horses

Abstract

SummaryReasons for performing study: N-butylscopolammonium bromide (NBB) and xylazine are commonly used medications for the treatment of spasmodic colic and other forms of abdominal pain in horses. Both NBB and xylazine exert significant effects on the cardiovascular system and other vital systems of horses. Objective: To evaluate the effects of i.v. administration of NBB, xylazine, and the combination of NBB and xylazine on heart rate, other commonly measured physiological parameters, cardiac rhythm and blood pressure. Methods: Six mature horses of mixed breed were used. In a random cross-over design, each horse was given 0.3 mg/kg bwt of NBB i.v., 0.25 mg/kg bwt xylazine i.v., and a combination of 0.3 mg/kg bwt NBB and 0.25 mg/kg bwt xylazine. Heart rate, physiological parameters, cardiac rhythm and indirect blood pressure were recorded at timed intervals before and 60 min following administration. Results: Heart rate and blood pressure were significantly elevated immediately following administration of NBB or NBB with xylazine. Administration of NBB with xylazine resulted in significantly greater initial and peak blood pressure values than with NBB alone. Administration of xylazine resulted in a decrease in heart rate, with an initial increase in blood pressure followed by a decrease in blood pressure. Sinus tachycardia was seen with NBB, and NBB and xylazine administration. First and second degree atrioventricular block was identified with xylazine administration. Ventricular tachycardia was identified in one horse following NBB and xylazine administration. Conclusions: Results of this study suggest that the effects of administration of NBB alone or in combination with xylazine to horses with colic, especially to those with systemic cardiovascular compromise, should be considered carefully to assess condition and predict prognosis accurately, and to avoid potential adverse effects.

Hyoscine-N-butylbromide premedication on cardiovascular variables of horses sedated with medetomidine

“…; Morton et al. ). In the present study, hyoscine IV increased HR above baseline for 20 minutes, and IM administration increased HR at T15–T30.…”

“…; Morton et al. ). Hypertension was associated with increased peripheral vascular resistance (Bryant et al.…”

“…; Morton et al. ). The hypertension caused by hyoscine occurred with an increase in HR and CO. Hyoscine alone does not increase MAP significantly (Geimer et al.…”

Pharmacological characterization of muscarinic receptors in the contractions of isolated bronchi in the horse

“…Indeed, selective M 1 receptor antagonist, telenzepine, was ineffective in improving airway function in human COPD patients (Ukena et al ., ). However, a mixed M 1 /M 3 antagonist might be a promising therapeutic tool in order to achieve good bronchodilation while minimizing side effects due to M 2 activation, like tachycardia (Morton et al ., ). Accordingly, tiotropium, an anticholinergic drug endowed with high M 1 /M 3 kinetic selectivity, resulted more effective than nonselective ipratropium in a clinical trial on human patients with COPD (Lee et al ., ), and revatropate, a selective M 1 /M 3 antagonist, showed excellent bronchodilatant activity and few adverse effects in humans and horses (Lee et al ., ; Morton et al ., ; McGorum et al ., ).…”

On the question of colic: Are answers beginning to emerge?

“…Lignocaine has been shown to have in vitro effects on jejunal smooth muscle [36], but although it is widely used as an anti-inflammatory agent in equine critical patients, in an experimental model no significant differences were found in inflammatory gene expression in lignocaine-treated and control groups in the black walnut extract model of laminitis, calling into question its use as an anti-inflammatory. Likewise, the ideal analgesic for use in colic patients has yet to be established; both xylazine and N-butylscopolammonium bromide have significant cardiovascular effects, which may, at the very least, influence clinical findings, and their effects should be borne in mind when assessing the colicking horse [37]. Opiates have traditionally been avoided for fear of potential adverse effects on gastrointestinal motility, but a recent study has shown that selective m agonists, without anticholinergic activity, may have less risk than other opiates, but again these studies are based on in vitro work and do not yet translate to clinical practice.…”