Effect of romifidine on the nociceptive withdrawal reflex and temporal summation in conscious horses

Abstract

Results confirm antinociceptive activity of romifidine and may represent an objective demonstration of the well-known hypersensitivity to tactile stimuli observed in horses receiving alpha2-adrenoreceptor agonists in clinical practice. Romifidine can be included in analgesic and anesthetic protocols to provide additional analgesia in horses.

Antinociceptive effects of three escalating dexmedetomidine and lignocaine constant rate infusions in conscious horses

“…The antinociceptive effects of α2 agonists in horses are well established (Jochle and Hamm, 1986;Moens et al, 2003;Spadavecchia et al, 2005;Dirikolu et al, 2006;Rohrbach et al, 2009). Dexmedetomidine induces antinociception in conscious dogs, cats, rats and human beings (Sabbe et al, 1994;Slingsby et al, 2009;Aydogan et al, 2013;Kosharskyy et al, 2013) and reduces the requirements for inspired anaesthetic gas in dogs (Pascoe et al, 2006;Uilenreef et al, 2008), cats (de Souza et al, 2010 and horses (Gozalo-Marcilla et al, 2013a, 2013b, 2013c.…”

“…The NWR threshold is the stimulus intensity needed to elicit an NWR, while the nociceptive tolerance is the maximum stimulus intensity tolerated by an individual. The NWR is used as a neurophysiological tool to investigate nociceptive processing and pharmacological modulation of nociception in human beings and veterinary species (Willer, 1977;Willer and Bathien, 1977;Arendt-Nielsen et al, 1995;Spadavecchia et al, 2005;Bergadano et al, 2009). An increase in NWR threshold and nociceptive tolerance, and a decreasing reflex response following administration of a drug, may be used as quantitative indicators of the drug's antinociceptive effect (Ercoli and Lewis, 1945;Spadavecchia et al, 2005).…”

The model of the Nociceptive Withdrawal Reflex in horses

“…Another important finding was that the relative reflex amplitude in the epoch 30 -80 ms increased after romifidine administration, suggesting a facilitation of reflex components of non-nociceptive origin when repeated stimulations were applied (Spadavecchia et al 2005). This could represent an electrophysiological correlate of the hypersensitivity to tactile stimuli observed in horses receiving alpha-2 agonists in clinical practice, known for many years and responsible for the sudden reactions even under profound sedation (Alitalo 1986, Freeman andEngland 2000).…”

“…From the results obtained in horses it appears that the experimental model applied to quantitatively assess temporal summation is valid and reliable and can be used as an additional tool to assess efficacy of analgesic drugs in these species (Spadavecchia et al 2005, Rohrbach et al 2009). …”

“…Alpha-2 agonists, widely used in the equine veterinary practice for sedation and analgesia, were the first drugs chosen to test modulation of NWR and temporal summation in horses (Spadavecchia et al 2005). Several authors reported about their analgesic efficacy under experimental conditions, using both visceral and somatic pain models (Kamerling et al 1988, Elfenbein et al 2009, Robertson and Sanchez 2010.…”