Effects of treatment with oxytocin, xylazine butorphanol, guaifenesin, acepromazine, and detomidine on esophageal manometric pressure in conscious horses

Objective—To compare effects of oxytocin, acepromazine maleate, xylazine hydrochloride-butorphanol tartrate, guaifenesin, and detomidine hydrochloride on esophageal manometric pressure in horses. Animals—8 healthy adult horses. Procedure—A nasogastric tube, modified with 3 polyethylene tubes that exited at the postpharyngeal area, thoracic inlet, and distal portion of the esophagus, was fitted for each horse. Amplitude, duration, and rate of propagation of pressure waveforms induced by swallows were measured at 5, 10, 20, 30, and 40 minutes after administration of oxytocin, detomidine, acepromazine, xylazine-butorphanol, guaifenesin, or saline (0.9% NaCl) solution. Number of spontaneous swallows, spontaneous events (contractions that occurred in the absence of a swallow stimulus), and high-pressure events (sustained increases in baseline pressure of > 10 mm Hg) were compared before and after drug administration. Results—At 5 minutes after administration, detomidine increased waveform amplitude and decreased waveform duration at the thoracic inlet. At 10 minutes after administration, detomidine increased waveform duration at the thoracic inlet. Acepromazine administration increased the number of spontaneous events at the thoracic inlet and distal portion of the esophagus. Acepromazine and detomidine administration increased the number of high-pressure events at the thoracic inlet. Guaifenesin administration increased the number of spontaneous events at the thoracic inlet. Xylazine-butorphanol, detomidine, acepromazine, and guaifenesin administration decreased the number of spontaneous swallows. Conclusions and Clinical Relevance—Detomidine, acepromazine, and a combination of xylazine butorphanol had the greatest effect on esophageal motility when evaluated manometrically. Reduction in spontaneous swallowing and changes in normal, coordinated peristaltic activity are the most clinically relevant effects. (Am J Vet Res 2002;63:1738–1744)