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Query: UMLS:C0030193 (pain)
 261,466 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The effect of systemic (intravenous) medetomidine, an alpha-2 adrenoceptor agonist, on pain thresholds was studied in healthy human subjects (n = 6). Medetomidine produced a dose-dependent (cumulative doses: 25 and 50 micrograms) sedative effect evaluated by visual analog scale. Also, a dose-dependent decrease of blood pressure but not of heart rate was seen after administration of medetomidine. Pain threshold to electric stimulation of the tooth pulp and cutaneous heat pain threshold were uninfluenced by medetomidine. An index of cutaneous thermal sensitivity to innocuous stimuli, the width of the thermoneutral zone, also was uninfluenced by medetomidine. Medetomidine produced a significant attenuation of the affective-motivational component (unpleasantness) of tourniquet-induced ischemic pain, whereas the sensory-discriminative component (pain magnitude estimate) of the ischemic pain was not attenuated. The results suggest that systemic medetomidine alone at subanesthetic but sedative and hypotensive doses does not significantly influence the intensity and thresholds of experimental pain, whereas the affective-motivational component of pain can be attenuated.
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PMID:Effect of systemic medetomidine, an alpha 2 adrenoceptor agonist, on experimental pain in humans. 167 Sep 12

Medetomidine, a new alpha 2-adrenoceptor agonist produced dose-dependent (30-100 micrograms/kg i.p.) analgesia in the formalin test in rats, and this effect was reversed by atipamezole (1 mg/kg), a new alpha 2-adrenoceptor antagonist. However, medetomidine at the dose of 100 micrograms/kg did not influence tail flick latencies or latencies of the biting response to mechanical pinch stimuli. Moreover, medetomidine produced sedation and a decrease in locomotor activity. In comparison, the non-sedative monoaminergic agent, cocaine (25 mg/kg), produced highly significant analgesic effects in the formalin and mechanical pain tests. The cocaine effect in the formalin test was not reversed by atipamezole (1 mg/kg). It is concluded that the analgesic effect of medetomidine in the formalin test is due to supraspinal mechanisms related to sedation and is mediated by alpha 2-adrenoceptors. The alpha 2-adrenoceptors are not involved in cocaine-induced anagesia.
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PMID:The effect of medetomidine, an alpha 2-adrenoceptor agonist, in various pain tests. 197 6

The sedative and analgesic effects of medetomidine were studied in 18 laboratory beagles in a randomized cross-over study which was carried out in a double-blind fashion. Xylazine was included as a positive control and placebo as a negative control. Medetomidine was used at doses of 10, 30, 90 and 180 micrograms/kg i.m. compared to a dose of 2.2 mg/kg xylazine i.m. Parameters closely related to sedation were used to measure the degree of sedation. These were a posture variable (including evaluation of the dog's posture without external disturbance and resistance when laid recumbent) and a relaxation variable (including relaxation of the jaws, upper eyelids and anal sphincter). The first signs of sedation were recorded 1.5-3.5 min after administration of both drugs. The dogs sat down at 0.6-2.6 min post-injection and became prone at 1.9-5.9 min. Medetomidine dose-dependently affected the posture of the dogs and the relaxation variable--the higher the dose, the stronger and longer lasting the effect recorded. The sedative effect of xylazine was comparable to a medetomidine dose of 30 micrograms/kg. The analgesic effect was assessed as changes in the response to superficial pain induced by electrical stimuli. The response threshold increased significantly with both drugs and the effect of medetomidine was dose-dependent. The effects of the doses of 30 micrograms/kg medetomidine and 2.2 mg/kg xylazine did not differ significantly. In summary, medetomidine possessed an excellent sedative effect associated with analgesia in dogs.
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PMID:Sedative and analgesic effects of medetomidine in dogs. 256 98

Experiments with 3 doses of medetomidine (20, 40 and 80 micrograms/kg, iv. and im., respectively) were carried out on 90 dogs of 16 breeds in the Small Animal Surgery of the University of Veterinary Science, Budapest. Changes in hematology as well as in AST, AP, BUN, creatinine were studied. Medetomidine administered iv deepened the sedation and lengthened tranquillization dose-dependently. After im administration the sedative effect was still dose-dependent, but the duration of its clinical effectiveness could not be lengthened significantly. The development of the sedation could however, be quickened. The iv administration increased the level of analgesia in proportion to dosage; the im application could change the level of pain-killing effect of the drug, but could not lengthen it. According to the laboratorical determinations, regardless of the dosage and the route of application, medetomidine did not affect the AST and AP enzyme activities, or the BUN and creatinine values.
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PMID:Clinical investigations of medetomidine in dogs. 257 Dec 68

The sedative effects of medetomidine at doses of 20 and 40 micrograms/kg im given alone or followed 16-18 min later by fentanyl (2 micrograms/kg iv) was investigated in 6 bitches of mixed breeds. The higher dose of medetomidine alone caused the greater degree of sedation, but two bitches were only lightly sedated with either dose. Side effects noted in some cases included apparent pain on injection, vomiting on induction of sedation, bradycardia, slowing of respiratory rate, cyanosis and muscular twitching. The intravenous injection of fentanyl caused a marked increase in depth of sedation in all animals, inducing a condition similar to neuroleptanaesthesia in which the eyes were rotated downward and the pedal reflex abolished. Slight twitching and sensitivity to sound occurred immediately after fentanyl injection, but this was transient. The cardiopulmonary effects of medetomidine (40 micrograms/kg im) followed 20 min later by either fentanyl (2 micrograms/kg iv) or a saline placebo were investigated in 4 beagle dogs. Medetomidine caused bradycardia, hypotension and reduced respiratory rate, inducing an intermittent respiratory pattern. The iv injection of fentanyl did not further alter the heart or respiratory rate or blood pressure. However there was a small but significant decrease in arterial oxygen tension and rise in arterial carbon dioxide tension. indicating some respiratory depression. We conclude that the use of intravenous fentanyl to dogs already sedated with medetomidine could prove useful in clinical cases where the initial sedation with medetomidine has proved inadequate.
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PMID:The use of medetomidine/fentanyl combinations in dogs. 257 Dec 71

The analgesic effect of medetomidine was studied in ten laboratory beagles. The doses of medetomidine used were 10, 30 and 80 micrograms/kg BW. Xylazine (3 mg/kg BW) was included as a positive control and placebo as a negative control. The test utilized two independently randomized Latin square designs (5 x 5) and was carried out in a double blind fashion. Noxious stimuli were induced with a round pointed thermal probe which was set to produce a temperature of +44.9 +/- 0.2 degrees C. The wall of the external auditory canal was touched with the heated point of the probe. The time period from the start of the attachment to the avoidance reflex was measured and recorded as response time. To avoid tissue damage the heat treatment was stopped after 5 s even though the dog did not respond. Medetomidine clearly prolonged the response time. At the highest dose of medetomidine (80 micrograms/kg) all dogs reached the analgesic stage where they did not respond to the heat treatment. At 30 micrograms/kg of medetomidine half of the dogs had a prolonged response time. The lower dose of 10 micrograms/kg had no appreciable effect. Xylazine-induced analgesia was comparable to that of 30 micrograms/kg of medetomidine: half of the dogs lost their avoidance reflex. In conclusion, medetomidine proved to have a dose dependent analgesic effect in experimental auricular pain in dogs.
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PMID:Effects of medetomidine on the experimental auricular pain in dogs. 257 Dec 72

The sedative action of alpha 2-adrenergic agonists is generally ascribed to inhibition of the locus coeruleus (LC) and its ascending activating projection to the forebrain, although postsynaptic effects in the neocortex may also play a part. The sedative effect of the drugs varies considerably between different species. Systemic application of alpha 2-adrenergic agents have analgesic effects in addition to their sedative actions. Descending noradrenergic projections from the LC area modulate pain transmission at the spinal level. The purpose of this trial was to investigate the sedative properties of medetomidine in the cat. Medetomidine was injected intramuscularly at dose rates of 0.02, 0.06 and 0.18 mg/kg. Xylazine 3.0 mg/kg and saline were used for comparison. Medetomidine increased drowsy waking at the expense of both arousal and sleep. Nociceptive reflexes were suppressed in the case of the smallest dose of medetomidine, and abolished by the others. The 0.18 mg/kg dose of medetomidine had approximately equal effect on vigilance as 3.0 mg/kg of xylazine. The duration of the effect of medetomidine was dose-dependent. The alpha-receptor blocker phentolamine i.m. reversed the heavy sedation produced by medetomidine. Medetomidine also produced significant bradycardia, but the duration of this effect was not dose-dependent.
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PMID:Physiological role of alpha 2-adrenoceptors in the regulation of vigilance and pain: effect of medetomidine. 257 Dec 74

A study was made of the effects of different volumes of injection product, adrenaline, the alpha 2-adrenoceptor-agonist medetomidine and Mycobacterium butyricum on epidural sufentanil in the rat. Increasing the volume of epidural sufentanil, and similarly decreasing the concentration of the injection product, resulted in a potentiation of the analgesic properties of epidural sufentanil without affecting the effects of the drug on the pinna and cornea reflexes and on muscle tonus. An analogue effect was observed if rats were tested for epidural analgesia during a chronic pain phase after inoculation with Mycobacterium butyricum. Adding adrenaline to epidural sufentanil also resulted in an increased analgesia but there was also a minor potentiation of all other behavioural parameters measured. The alpha 2-adrenoceptor-agonist medetomidine, clearly potentiated all behavioural effects induced by epidural sufentanil. As a consequence, there was no gain in specificity for epidural analgesia. Medetomidine, however, clearly reversed the normally observed skeletal muscle rigidity into a muscle hypotonia. Globally, these results thus indicate that manipulations of the volume of injection, the additional treatment with other drugs and the pain state of the animal can alter the activity of epidural sufentanil. Therefore, it might be concluded that the differences in the duration of analgesia observed with epidural sufentanil between human and animal studies can be partially explained in terms of differences between the experimental conditions.
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PMID:Effects of adrenaline, an alpha 2-adrenoceptor agonist, the volume of injection, and the global pain state of the animal on the activity of epidural sufentanil. 257 73

Effects of the selective alpha 2-adrenoceptor agonist, medetomidine, on a compound volley of a tibial nerve stimulation-evoked spinal reflex, pain-induced phrenic motor responses and on postoperative neuropathic pain behavior were studied in rats. Medetomidine (0.3 mg/kg) decreased the amplitude of the compound volley recorded from peroneal nerve in response to tibial stimulation in pentobarbital (40 mg/kg) anesthetized rats. Atipamezole, an alpha 2-adrenoceptor antagonist (1.5 mg/kg) fully restored the response when given 60 min after the medetomidine administration. Pain-evoked phrenic motor responses were completely inhibited upon combination anesthesia by pentobarbital (40 mg/kg) and medetomidine (0.3 mg/kg) (PB+M) but not upon plain pentobarbital anesthesia (50 or 60 mg/kg) (PB50,PB60). To study the effect of medetomidine on postoperative neuropathic pain behavior (autotomy), transection of sciatic nerve was done under PB+M, PB50 or PB60 anesthesia. No differences between the groups were found in the postoperative pain behavior during eight-week follow up. The results show that activation of alpha 2-adrenergic receptors by medetomidine under pentobarbital anesthesia mitigates trauma-induced afferent barrage, whereas it does not reduce the subsequent autotomy.
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PMID:Activation of alpha 2-adrenergic receptors decreases nerve trauma-induced afferent barrage but not autotomy. 775 90

Twelve laboratory beagles underwent a routine left thoracotomy to insert permanent instrumentation. Every second dog was given 10 micrograms/kg of medetomidine, an alpha 2-agonist sedative. The rest of the animals were treated with 20 micrograms/kg of buprenorphine, an opioid agonist-antagonist, which is regularly used to treat postoperative pain in laboratory animals. The drugs were given at the end of operation (0) and 4, 8, 20, and 24 h postoperatively. Blood samples for catecholamines (adrenaline and noradrenaline) and blood gases (pCO2 and pO2) and pH were drawn immediately before any drug administration, and 30 min later. At the same time points, the pain level was subjectively evaluated using a pain score, and heart rate and rectal temperature were measured. Adrenaline and noradrenaline concentrations were lower in the medetomidine group than in the buprenorphine group. Accordingly, it was concluded that medetomidine had better analgesic effect than buprenorphine in the treated animals. This result was supported by subjective evaluation of the severity of pain, even though subjective evaluation is not considered very reliable in the present kind of open studies. pO2 was lower in the buprenorphine group than in the medetomidine group after the first injection of the analgesics. pCO2 and pH were similar in both of the groups. Medetomidine decreased heart rate after every injection, this fall and subsequent rise might be avoided by a lower dose regime. Buprenorphine did not effect heart rate. Rectal temperature did not differ in either group. It was concluded that medetomidine, and other alpha 2-agonists, possess some potential in postoperative pain alleviation.
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PMID:Medetomidine, an alpha 2-agonist, alleviates post-thoracotomy pain in dogs. 783 Mar 78


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