Sedative and analgesic effects of detomidine or detomidine and butorphanol in the donkey

Abstract

There are approximately forty two million donkeys in the world. All developing countries have an expanding population of donkeys, which are used for the provision of various services. The most commonly performed procedures in donkeys are castrations, tumour removals, foot care and dental treatments. All of these procedures can be performed in standing donkeys provided sufficient analgesia and sedation are provided. The donkey should be recognised and treated in its own light. Very few analgesics relieve pain without producing side effects. The ideal analgesic would provide good analgesia and sedation without any side effects. Combined with sedation, analgesia aids in the handling of animals and reduces the danger to attendants. Neuroleptanalgesia provides a more potent sedative and analgesic allowing more procedures to be performed. A marked synergistic effect between opioids and alpha2 adrenergic agonists is reported. Detomidine-butorphanol is used extensively for equine sedation and analgesia in the United States of America and Europe. Currently there is limited information available on effective sedative and analgesic drugs or drug combinations in donkeys. Detomidine and xylazine, which belong to the alpha2 adrenergic agonist group, have been described for use in donkeys. No information exists on the use of opioid drugs or opioid-sedative combinations in donkeys. Detomidine produces sedation and analgesia of a greater magnitude and a longer duration than xylazine. Detomidine has been used to sedate horses for diagnostic, therapeutic or minor surgical procedures and as part of a premedication or an intravenous anaesthetic protocol. Detomidine is a good analgesic. The duration of sedation and analgesia is dose dependent. The sedation produced by detomidine alone is not always satisfactory and some horses will respond to noxious stimuli with well-directed kicks. For this reason, detomidine and butorphanol are very often combined. Butorphanol is a synthetic mixed agonist-antagonist opioid. The detomidine is given five minutes before the administration of butorphanol or the butorphanol can follow the detomidine. Sedation is easily extended by additional doses of detomidine and/or butorphanol. This combination produces profound sedation in which horses are apparently unaffected by sounds, tactile stimuli and surrounding activity. It has been suggested that donkeys require a higher dose of detomidine for sedation than horses. The recommended dose for donkeys is 20-40 µg/kg. The degree and length of analgesia and sedation is dose dependent. A dose of 5-10 µg /kg was found effective for sedation and a dose of 20 µg /kg was effective for sedation and analgesia. No recommended doses for butorphanol in donkeys exist. Twelve healthy male donkeys were randomly divided into two groups. One group received 10 µg/kg of detomidine while the other group received 10 µg /kg of detomidine and 25 µg /kg of butorphanol. Sedation was evaluated by a scoring system and characterised by lowering of the head, relaxation of the upper eyelids, drooping of the lower lip and dropping of the ears. Analgesia was evaluated by means of a pinprick method. The average dose for detomidine was 11.24 µg/kg and that of butorphanol was 28.0 µg/kg. The onset time to sedation was 4 minutes 21 seconds with detomidine alone and 3 minutes 28 seconds with the combination. The average length of sedation for the detomidine group was 20 minutes, and for the detomidine-butorphanol group was 1 hour and 7 minutes. The analgesia lasted twice as long in combination group compared to the detomidine group. Detomidine did not eliminate coronary band pain. Heart rates dropped significantly in the first minute after the injection in both groups, and this was statistically significant. There was however no statistical difference between the two groups. An atrioventricular and a sinoatrial block were recorded during this trial. The respiratory rates tended to decrease in the first few minutes after which the rate stabilised. Four donkeys receiving butorphanol had Cheyne-Stokes respiratory patterns. It was evident that the combination of detomidine and butorphanol produced a greater sedative and analgesic effect than detomidine alone. The superior sedation is the result of synergistic effects between detomidine and butorphanol. This trial has shown that detomidine in combination with butorphanol in donkeys produces sedation that is superior to detomidine on its own and last at least twice as long. Analgesia was dramatically improved with the combination as compared to detomidine alone.