Effects of Metoclopramide on the Gastrointestinal Tract Motility of Hispaniolan Parrots (Amazona ventralis)
Department of Surgical Sciences, School of Veterinary Medicine, University of Wisconsin-Madison, Madison, WI 53706 USA
In mammalian species, upper gastrointestinal stasis is often empirically treated with metoclopramide (Reglan®), a prokinetic drug. Although metoclopramide is most effective when motility is diminished or impaired, studies in healthy cats and dogs have shown that gastric contractility and emptying are increased post-metoclopramide administration.3,6 In avian medicine, metoclopramide has been used in patients with crop stasis, proventricular dilatation, regurgitation, vomiting, and/or intestinal ileus with some reported success.4,5 The empirical dosage recommended for psittacine species is 0.5 mg/kg intramuscularly every 8–12 hours.1,4,5 Although this dosage is published in many avian veterinary references and formularies, it has been extrapolated from the mammalian literature. There have been no systematic studies evaluating the pharmacokinetics of metoclopramide in birds or its effects on gastrointestinal motility.
This study evaluated the effects of metoclopramide on the gastrointestinal tract motility of 14 adult Hispaniolan parrots (Amazona ventralis) using fluoroscopy and radiography as imaging modalities. Each parrot (n=14) was manually restrained and gavaged with 30 ml/kg of iohexol (Omnipaque®, Nycomed Inc., Princeton, NJ) into the crop.1,2 Immediately after iohexol administration, each bird was allowed to perch in a restraint box for fluoroscopy. The use of a restraint box restricted the bird’s activity while minimizing stress-induced changes in gastrointestinal motility. The contractility of the thoracic esophagus (number of iohexol boluses/5 min) and proventriculus and ventriculus (number of contractions/5 min) was determined. These measures were averaged over a 10-minute period and used as baseline controls for each bird.
Following fluoroscopy, the birds were placed on an acrylic restraint board for radiography. Two radiographic films (lateral and ventrodorsal views) were obtained at 30 minutes, 1 hour, then hourly until 8 hours post-iohexol administration. These radiographs were analyzed by SVM radiology staff and used to determine the emptying and transit times of iohexol through the crop, proventriculus, ventriculus, and intestine. These data were used as baseline controls for each bird.
After control values were established, the parrots were randomly assigned to three groups of seven birds each (seven birds were utilized twice). All birds were rested for at least 7 days between trials. Each group of birds was given metoclopramide (Metoclopramide Injection, USP, Gensia SICOR Pharmaceuticals, Irvine, CA) via intramuscular injection into the pectoral musculature. The first group was administered metoclopramide at the published recommended psittacine dosage of 0.5 mg/kg.1,4,5 Groups 2 and 3 received metoclopramide at dosages of 0.75 and 1.0 mg/kg, respectively. Each bird was gavaged with 30 ml/kg of iohexol 5 minutes after metoclopramide administration, and the contrast study was repeated as described above for the controls. The radiology staff remained blind to the dose of metoclopramide administered to each bird during the radiographic interpretation of contractility and transit/emptying times.
Mean thoracic esophageal contractility in control birds was 11.4 boluses/minute (±0.23 SD). Mean proventricular/ventricular contractility in control birds was 2.86 contractions/minute (±0.64 SD). Contrast media was noted throughout the entire gastrointestinal tract in the majority of untreated birds within the first 30 minutes of the study. On average, clearance of contrast media from the crop occurred by 5 hours and clearance from the proventriculus by 6 hours post-administration. Contrast media was still present within the ventriculus and intestines in the majority of birds by 8 hours post-administration.
Administration of metoclopramide at 0.5, 0.75, and 1.0 mg/kg did not significantly affect the contractility of the thoracic esophagus or proventriculus/ventriculus in the study birds. On average, the clearance of contrast media from the crop and proventriculus occurred by 4 hours post-administration in the 0.75 and 1.0 mg/kg study groups. Average clearance from the ventriculus was noted by 6 hours post-administration in these groups. Average clearance of contrast media from the crop and proventriculus in the 0.5 mg/kg group was 6 hours post-administration, with ventricular clearance by 7 hours. The clearance rates in the treatment groups did not differ significantly from the control group.
Results of this study indicate that the administration of metoclopramide intramuscularly at dosages of 0.5, 0.75, and 1.0 mg/kg does not significantly alter the gastrointestinal motility in healthy adult Hispaniolan parrots. Further studies are recommended to determine whether metoclopramide alters the gastrointestinal motility of birds with gastrointestinal stasis.
The authors would like to thank Dr. Jodi Matheson for her technical assistance during this project.
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