羅米非定 Romifidine HCl

作用機轉

A potent alpha2-adrenergic agonist, romifidine is classified as a sedative/analgesic with muscle relaxant properties. Alpha-2 receptors are found in the CNS and several tissues peripherally; both presynaptically and postsynaptically. In the CNS, the primary action is a feedback inhibition of norepinephrine release. Opioids and alpha-2 agonists may have synergistic analgesic effects. Pharmacologic effects of romifidine include sedation, analgesia, and reduced catecholamine release from the CNS. Thermoregulatory mechanisms may be altered. Peripherally, an initial vasoconstrictive response occurs with increases in blood pressure. Within minutes a hypotensive phase occurs. Heart rate can significantly decrease secondary to a vagal response to hypertension. A second-degree atrioventricular block may also occur. Antimuscarinic agents can prevent bradycardia, but their use is controversial as they can potentially cause hypertension, increased myocardial oxygen demand, and reduced GI motility. Alpha-2 agonists can transiently slow duodenal motility and increase micturation in horses and can inhibit insulin release from pancreatic islet cells resulting in hyperglycemia. Other effects seen in horses in romifidine hcl 805 806 romifidine hcl clude sweating, mydriasis, decreases in hematocrit, and increased uterine pressure in non-pregnant mares. In horses, when compared with other alpha-2 agonists (xylazine, detomidine, medetomidine), romifidine does not appear to cause as much ataxia at sedative dosages and has the longest duration of sedation. Duration of analgesia is shorter than the duration of ­sedation.