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1.
OBJECTIVE: To determine the cardiorespiratory effects of epidural administration of morphine alone and in combination with fentanyl in dogs anesthetized with sevoflurane. DESIGN: Prospective study. ANIMALS: 6 dogs. PROCEDURE: Dogs were anesthetized with sevoflurane and allowed to breathe spontaneously. After a stable plane of anesthesia was achieved, morphine (0.1 mg/kg [0.045 mg/lb]) or a combination of morphine and fentanyl (10 microg/kg [4.5 microg/lb]) was administered through an epidural catheter, the tip of which was positioned at the level of L6 or L7. Cardiorespiratory variables were measured for 90 minutes. RESULTS: Epidural administration of morphine alone did not cause any significant changes in cardiorespiratory measurements. However, epidural administration of morphine and fentanyl induced significant decreases in diastolic and mean arterial blood pressures and total peripheral resistance. Stroke volume was unchanged, PaCO2 was significantly increased, and arterial pH and base excess were significantly decreased. Heart rate was significantly lower after epidural administration of morphine and fentanyl than after administration of morphine alone. None of the dogs had any evidence of urine retention, vomiting, or pruritus after recovery from anesthesia. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggest that epidural administration of morphine at a dose of 0.1 mg/kg in combination with fentanyl at a dose of 10 microg/kg can cause cardiorespiratory depression in dogs anesthetized with sevoflurane.  相似文献   

2.
Nineteen dogs were assigned randomly to one of three groups. Animals in Group 1 were pre-medicated with acepromazine, 50 μg/kg bodyweight (bwt) intramuscularly (im) and received 10 ml of 0.9 per cent saline intravenously (iv) at the time of skin incision. Dogs in Group 2 were pre-medicated with acepromazine, 50 μg/kg bwt im, and received fentanyl 2 μg/kg bwt iv at skin incision. Dogs in Group 3 were pre-medicated with acepromazine, 50 μg/kg bwt and atropine, 30 to 40 μg/kg bwt, im and received fentanyl, 2 μg/kg bwt iv at skin incision. Pulse rate, mean arterial blood pressure, respiratory rate and end tidal carbon dioxide were measured before and after fentanyl or saline injection. Fentanyl caused a short-lived fall in arterial blood pressure that was significant in dogs premedicated with acepromazine, but not in dogs pre-medicated with acepromazine and atropine. A significant bradycardia was evident for 5 mins in both fentanyl treated groups. The effect on respiratory rate was most pronounced in Group 3, in which four of seven dogs required intermittent positive pressure ventilation (IPPV) for up to 14 mins. Two of six dogs in Group 2 required IPPV, whereas respiratory rate remained unaltered in the saline controls. The quality of anaesthesia was excellent in the fentanyl treated groups; however, caution is urged with the use of even low doses of fentanyl in spontaneously breathing dogs under halothane-nitrous oxide anaesthesia.  相似文献   

3.
The locomotor responses of horses given morphine and fentanyl were blocked or lessened by administration of naloxone or acepromazine. Naloxone given at the dosage of 0.015 mg/kg completely blocked the locomotor activity induced in horses given fentanyl (0.020 mg/kg of body weight). The locomotor stimulation produced by morphine given at the dosage of 2.4 mg/kg was reduced by 75% of naloxone (0.020 mg/kg). Acepromazine partially blocked the locomotor responses to fentanyl and morphine. This blockade activity reached its peak about 30 minutes after acepromazine was given (IV) and lasted more than 6 hours. Simultaneous administration of acepromazine and morphine was associated with substantial respiratory depression for more than 4 hours after administration of both drugs. In other experiments, fentanyl did not add to the partial locomotor response observed after large doses of pentazocine were given--this being consistent with the concept that pentazocine possesses both antagonist and agonist actions at the narcotic receptor. Furosemide and phenylbutazone, given at usually used clinical doses, had no effect on the locomotor response to fentanyl, indicating that the usual clinical dosages of neither drug exerted stimulant or depressant actions.  相似文献   

4.
Objective To measure the plasma fentanyl concentrations achieved over time with transdermal fentanyl patches in awake cats and cats undergoing anesthesia and ovariohysterectomy. Study design Randomized prospective experimental study. Animals Twenty‐four purpose‐bred cats. Methods Cats were randomly assigned to three groups for Part I of a larger concurrent study. Group P received only a 25 μg hour?1 transdermal fentanyl patch. Group P/A received the patch and anesthesia. Group A received only anesthesia. After a minimum 1‐week washout period, the cats were randomly reassigned to two groups for Part II of the larger study. Group P/A/O received the patch, anesthesia and ovariohysterectomy. Group A/O received anesthesia and ovariohysterectomy. Patches were left in place for 72 hours and plasma samples were obtained for fentanyl analysis while the patches were in place, and for 8 hours after patch removal for cats in Group P, P/A, and P/A/O. Results The 25 μg hour?1 transdermal fentanyl patches were well tolerated by the cats in this study (mean body weight of 3.0 kg) and no overt adverse effects were noted. Mean plasma fentanyl concentrations over time, mean plasma fentanyl concentrations at specific times (8, 25, 49, and 73 hours after patch placement), time to first detectable plasma fentanyl concentration, time to reach maximum plasma fentanyl concentration, maximum plasma fentanyl concentration, mean plasma fentanyl concentration from 8 to 73 hours, elimination half‐life, and total area under concentration (AUC) were not statistically different among the groups. Conclusions Halothane anesthesia and anesthesia/ovariohysterectomy did not significantly alter the plasma fentanyl concentrations achieved or pharmacokinetic parameters measured, when compared with awake cats. There was a high degree of individual variability observed both within and between groups of cats in parameters measured. Clinical significance The high degree of variability observed suggests that careful observation of cats with fentanyl patches in place is required to assess efficacy and any potential adverse effects. Anesthesia and anesthesia/ovariohysterectomy do not appear to alter plasma fentanyl concentrations achieved by placement of a 25 μg hour?1 transdermal fentanyl patch when compared to cats not undergoing these procedures.  相似文献   

5.
Objective— To evaluate the effect of preoperative intrathecal administration of a low dose of morphine on intraoperative fentanyl requirements in dogs undergoing cervical and thoracolumbar spinal surgery.
Study Design— Prospective randomized clinical study.
Animals— Dogs (n=18) matched by surgical procedure administered intrathecal morphine (MG) or no-treatment (control group, CG).
Methods— After premedication with romifidine (4 μg/kg, intravenously) and induction with propofol, anesthesia was maintained with sevoflurane in oxygen. Intrathecal morphine 0.03 (0.023–0.034) mg/kg was administered at lumbar level 41 (25–65) minutes before surgery in MG. Ketamine (0.5 mg/kg) was administered hourly, starting before incision. Fentanyl infusion (1.2 and 4.2 μg/kg/h in MG and CG, respectively) was administered after a loading dose (5 and 10 μg/kg in MG and CG, respectively), and boluses were given if an increase >20% in heart rate and arterial blood pressure was observed. Total amount of fentanyl administered was recorded, to calculate hourly requirements and predict plasma concentration using a computer simulation.
Results— Hourly fentanyl consumption and predicted plasma concentrations at the time of response to surgery were significantly lower in MG compared with CG.
Conclusions— Preoperative administration of a low dose of intrathecal morphine has a sparing effect on intraoperative fentanyl requirements.
Clinical Relevance— Preoperative intrathecal administration of a low dose of morphine at the lumbar level represented a safe and effective mean of providing intraoperative analgesia in dogs undergoing cervical and thoracolumbar spinal surgery.  相似文献   

6.
Fentanyl is used in small animals for perioperative analgesia during anaesthesia. Severe bradycardia and asystole were observed on bolus administration of a 3 µg/kg loading dose of fentanyl in two dogs under isoflurane anaesthesia. Premedication with 10 µg/kg glycopyrrolate did not prevent asystole in the first case; and although bradycardia was treated with 5 µg/kg glycopyrrolate administered intravenously in the second case, the heart rate continuously decreased and asystole subsequently developed. Asystole in both cases was quickly corrected by intravenous administration of 0 · 04 mg/kg atropine and closed chest compressions. This case report describes asystole induced by fentanyl administration in isoflurane anaesthetised dogs. Atropine was more effective than glycopyrrolate in the treatment of fentanyl‐induced asystole.  相似文献   

7.
Opioids have an unjustified reputation for causing mania in cats, but with refinements in dosing they are now used successfully in this species. The mu-opioid agonists are generally considered the best analgesics. Morphine (0.1-0.3 mg/kg) is effective in a clinical setting. Methadone (up to 0.5 mg/kg) has a similar profile to morphine. Pethidine (Demerol, meperidine; 2-5 mg/kg) is a useful analgesic with a faster onset but shorter duration of action than morphine. Oxymorphone and hydromorphone (0.05-0.1 mg/kg) are widely used in the USA. These opioids are more potent (up to 10 times), and longer acting than morphine in cats. Butorphanol (0.1-0.4 mg/kg) is a mu-opioid antagonist that produces its analgesic actions through kappa agonist activity. It rapidly reaches a ceiling effect, is short acting and is a weaker analgesic than pure mu opioids. Buprenorphine (0.01-0.02 mg/kg), a partial mu-agonist, is the most popular opioid used in small animal practice in the UK, other parts of Europe, Australia and South Africa. In clinical studies it has produced better analgesia than several other opioids and appears to be highly suitable for perioperative pain management in cats. NSAIDs are also used in cats for pain management, although cats metabolise these differently from other species. With appropriate dosing, carprofen (1-4 mg/kg) and meloxicam (0.3 mg/kg) have proved highly effective with few side effects. The use of ketoprofen (2 mg/kg), tolfenamic acid (4 mg/kg) and vedaprofen (0.5 mg/kg) has been reported in cats. Other less traditional analgesics such as ketamine, medetomidine and local anaesthetics are also used for clinical pain management. The transmucosal, transdermal and epidural routes offer novel methods for administration of analgesic drugs and have considerable potential for improving techniques in feline pain management.  相似文献   

8.
Opioid overdose in dogs is manifested by clinical signs such as excessive sedation, bradycardia, and hypothermia. The ability of two different intramuscular (i.m.) naloxone reversal regimens to reverse the opioid-induced effects of a fivefold overdose of long-acting transdermal fentanyl solution was evaluated in dogs. Twenty-four healthy Beagles were administered a single 13 mg/kg dose (fivefold overdose) of transdermal fentanyl solution and randomized to two naloxone reversal regimen treatment groups, hourly administration for 8 h of 40 (n = 8) or 160 μg/kg i.m. (n = 16). All dogs were sedated and had reduced body temperatures and heart rates (HRs) prior to naloxone administration. Both dosage regimens significantly reduced sedation (P < 0.001), and the 160 μg/kg naloxone regimen resulted in a nearly threefold lower odds of sedation than that of the 40 μg/kg i.m. naloxone regimen (P < 0.05). Additionally, naloxone significantly increased the mean body temperatures and HR (P < 0.001), although the 160 μg/kg regimen increased body temperature and HR more (P < 0.05). However, the narcotic side effects of fentanyl returned within 1-3 h following termination of the naloxone dosage regimens. The opioid-induced effects of an overdose of transdermal fentanyl solution can be safely and effectively reversed by either 40 or 160 μg/kg i.m. naloxone administered at hourly intervals.  相似文献   

9.
Fentanyl citrate is a potent opioid that can be delivered by the transdermal route in cats and dogs. Publications regarding transdermal fentanyl patches were obtained and systematically reviewed. Seven studies in cats and seven studies in dogs met the criteria for inclusion in this review. Dogs achieved effective plasma concentrations approximately 24 hours after patch application. Cats achieved effective plasma concentrations 7 hours after patch application. In dogs, transdermal fentanyl produced analgesia for up to 72 hours, except for the immediate 0- to 6-hour postoperative period. In cats, transdermal fentanyl produced analgesia equivalent to intermittent butorphanol administration for up to 72 hours following patch application.  相似文献   

10.
The effects of preferential μ (morphine), selective μ (fentanyl), selective κ (compound U69593) opioid receptor agonists, and nonselective (naloxone) and selective μ (naloxonazine) antagonists on equine small intestinal motility were evaluated in vitro. Samples of circular muscle from equine jejunum were placed in isolated organ baths and drug-induced modifications of both spontaneous and electrically evoked contractile activity were measured. None of the opioid agonists induced a significant change in spontaneous contractions. Fentanyl and U69593 reduced electrically induced contractions, whereas morphine reduced them only slightly. Naloxone competitively antagonised U69593, but both naloxone and naloxonazine were unable to counteract the inhibition of contractions induced by fentanyl. The inhibition of contractions shown by fentanyl is therefore probably not mediated by opioid receptors, but due to an anticholinergic activity of this drug. In summary, these data showed an inhibitory effect exerted by κ receptors on equine small intestinal motility, whereas the role of μ receptors seemed marginal and would need further characterisation.  相似文献   

11.
The purpose of this study was to compare the pharmacokinetics of two highly protein‐bound, lipophilic opioid drugs. Fentanyl (10 μg/kg) and buprenorphine (20 μg/kg) were administered intravenously (IV) to six healthy greyhound dogs (three males and three females). The doses were based on clinically administered doses for dogs. Plasma drug concentrations were determined using liquid chromatography with mass spectrometry, and noncompartmental pharmacokinetics were estimated with computer software. The volume of distribution (area) was larger for fentanyl (7.42 L/kg) compared to buprenorphine (3.54 L/kg). The plasma clearance of fentanyl (38.6 mL·min/kg) was faster than buprenorphine (10.3 mL·min/kg). The terminal half‐life of fentanyl (2.22 h) was shorter than buprenorphine (3.96 h). Despite similar physicochemical properties including octanol–water partition coefficient and pKa, the pharmacokinetics of fentanyl and buprenorphine were not similar. Both fentanyl (84%) and buprenorphine (95–98%) are considered highly protein bound, but the differences in protein binding may contribute to the lack of similarity of pharmacokinetics in healthy dogs.  相似文献   

12.
This study compared plasma histamine concentrations, behavioral and cardiovascular parameters following intravenous administration of hydromorphone and morphine in conscious dogs. Five adult female dogs received a 15-sec bolus injection of saline, hydromorphone (0.1 and 0.2 mg/kg) or morphine (0.5 and 1.0 mg/kg) randomly at weekly intervals. Blood samples were collected from the jugular vein before and at 1, 2, 5, 15, 30, 60 and 120 min after drug administration. Plasma histamine concentration, noninvasive oscillometric blood pressure, heart rate and rhythm were evaluated. Data were analyzed with repeated measures anova and Tukey-Kramer post hoc test with a 5% significance level. Median plasma histamine increased significantly only after the higher dose of morphine. Maximum plasma histamine measured was 0.8 ng/mL after saline and, after the lower and higher doses, respectively, 10.2 and 9.7 ng/mL for hydromorphone, and 440 and 589 ng/mL for morphine. One dog became hypotensive immediately after receiving the highest dose of morphine. Occasional ventricular premature contractions occurred in one dog after both opioids and dosages. No dogs vomited or defecated, but all salivated profusely with both opioids. Neuroexcitation occurred in four dogs following each opioid. In conclusion, intravenous hydromorphone induced minimal histamine release and was well tolerated by these conscious healthy dogs.  相似文献   

13.
Cats (Felis catus) maintain greater blood Se concentrations compared with dogs (Canis familiaris) and, unlike dogs, show no signs of chronic Se toxicity (selenosis) when fed dietary organic Se (selenomethionine) concentrations of 10 μg/g DM. This study investigated the response of cats and dogs to high dietary concentrations of sodium selenite and organic Se to determine differences in metabolism between both species. In 2 consecutive studies, 18 adult cats and 18 adult dogs of with equal numbers of each sex were fed a control diet (0.6 μg Se/g DM) or the control diet supplemented to 8 to 10 μg Se/g DM from Na(2)SeO(3) or organic Se for 3 wk. All animals were fed the control diet 1 mo before the start of the study and blood samples were taken on d 0 and 21. The Se balance was assessed during the final week and a liver biopsy was obtained on the final day of the study. Measurements included plasma Se concentrations, plasma glutathione peroxidise (GPx) activities, plasma Se clearance, Se intake, and urinary Se excretion. No clinical signs of selenosis were observed in the cats or dogs, and apart from Se clearance, form of Se had no effect on any of the measurements. Apparent fecal Se absorption was greater in the dogs fed both forms of Se, while greater plasma Se concentrations were observed in the cats on both the control and supplemented diet (P = 0.034). Cats fed the supplemented diets had lower hepatic Se concentrations (P < 0.001) and excreted more Se in urine (P < 0.001) compared with dogs. Furthermore, cats fed the Na(2)SeO(3) supplement had greater Se clearance rates than dogs (P < 0.001). There was no effect of species on plasma GPx activity. We conclude that cats can tolerate greater dietary Se concentrations as they are more efficient at excreting excess Se in the urine and storing less Se in the liver.  相似文献   

14.
KuKanich, B., Hubin, M. The pharmacokinetics of ketoconazole and its effects on the pharmacokinetics of midazolam and fentanyl in dogs. J. vet. Pharmacol. Therap . 33 , 42–49.
Ketoconazole inhibits the Cytochrome P450 3A12 (CYP3A12) metabolizing enzyme as well as the p-glycoprotein efflux pump. The extent and clinical consequence of these effects are poorly understood in dogs. The objective was to assess the pharmacokinetics of ketoconazole after single and multiple doses and the effect of multiple doses of ketoconazole on midazolam (a known CYP3A12 substrate) and the opioid fentanyl. Six greyhound dogs were studied. The study consisted of three phases. Phase 1 consisted of i.v. midazolam (0.23 mg/kg base) and fentanyl (15.71 μg/kg base). Phase 2 consisted of a single oral dose of ketoconazole (mean dose 12.34 mg/kg). Phase 3 consisted of i.v. midazolam (0.23 mg/kg) and fentanyl (10 μg/kg) after 5 days of oral ketoconazole (12.25 mg/kg/day). Ketoconazole significantly inhibited its own elimination with the mean residence time ( MRT ) increasing from 6.24 h in Phase 1 to 12.54 h in Phase 3. Ketoconazole significantly decreased the elimination of midazolam, as expected, with the MRT increasing from 0.81 to 1.49 h. The elimination of fentanyl was not significantly altered by co-administration of ketoconazole with the MRT being 3.90 and 6.35 h. The MRT was the most robust estimate of decreased drug elimination.  相似文献   

15.
Fentanyl is a potent mu opioid receptor agonist that was discovered to identify an improved human health analgesic over morphine, an opioid frequently associated with histamine-release, bradycardia, hyper- or hypotension, and prolonged postoperative respiratory depression. Historically, the pharmacological features of fentanyl have been described primarily through the study of the human approved fentanyl citrate formulation. In conscious dogs, fentanyl has a wide margin of safety, possesses minimum effects on the cardiovascular and respiratory systems, and is readily reversible. Other pharmacological features include sedation, mild reductions in body temperature, and dose-dependent reduction in food intake. The short duration of effect of available fentanyl citrate solutions has limited its clinical use to perioperative injections or constant rate infusions (CRIs). To extend the analgesic effect, additional fentanyl delivery technologies have been developed for human health including the fentanyl patch that has been used in an extra-label manner in dogs. Beyond the slow onset and variability in fentanyl delivery, several additional disadvantages have precluded common use of patches in dogs. The recent approval of long-acting transdermal fentanyl solution for dogs provides a new approach for sustained delivery of fentanyl for the control of postoperative pain in dogs. It has a rapid onset of action, prolonged duration, and mitigates the disadvantages of oral, parenteral, and patch-delivered opioids. The availability of a safe and effective approved opioid in dogs may allow further optimization of postoperative analgesia in this species. The objective of this review is to summarize the history and pharmacology of fentanyl and to integrate information about the newly approved long-acting transdermal fentanyl solution.  相似文献   

16.
Objective-To investigate the effect of intraoperative extradural morphine administration on postoperative analgesia in dogs undergoing thoracolumbar spinal surgery to treat disk extrusion. Design-Prospective clinical trial. Animals-26 client-owned dogs undergoing thoracolumbar spinal surgery. Procedures-Animals were randomly allocated to receive morphine (0.1 mg/kg [0.045 mg/lb], extradurally) or no treatment (control group). Following preanesthetic medication with methadone (0.25 mg/kg [0.11 mg/lb], IM), anesthesia was induced with propofol and maintained with isoflurane or sevoflurane in oxygen. Lidocaine and fentanyl were administered during surgery in both groups at fixed rates. In the morphine administration group, morphine was splashed over the dura mater immediately prior to wound closure. Postoperative analgesia was assessed for 48 hours by assessors unaware of group allocation, and methadone was administered as rescue analgesic. Demographic characteristics, urinary output, days of hospitalization, and perioperative use of analgesics were compared via a Mann-Whitney U test. Results-Demographic data were similar between groups. In the morphine administration group, 2 of 13 dogs required postoperative methadone, and in the control group, methadone was administered to 11 of 13 dogs. The total number of doses of methadone administered in the 48 hours after surgery was 28 in the control group and 3 in the morphine administration group. No adverse effects were recorded in any group. Conclusions and Clinical Relevance-Intraoperative extradural morphine administration was effective in reducing postoperative analgesic requirement. Dogs undergoing thoracolumbar spinal surgery benefited from topical administration of preservative-free morphine administered directly on the dura mater as part of analgesic management.  相似文献   

17.
Data allowing rational use of analgesics in cats are limited. Pharmacokinetics and pharmacodynamics of fentanyl were studied in cats. Plasma fentanyl concentrations were measured using radioimmunoassay in a crossover study in six cats after 10 microg/kg (i.v.) or by application of fentanyl in pluronic lecithin organogel (PLO) to the inner ear pinna. On a separate occasion thermal thresholds were measured after i.v. fentanyl (10 microg/kg) or saline. Plasma fentanyl concentrations reached 4.7-8.31 ng/mL 2 min after i.v. administration and were undetectable after 95 min. Fentanyl was not detected in plasma at any time after PLO use. Thermal thresholds did not change following saline administration but were increased above baseline from 5 to 110 min after i.v. fentanyl. In this model a plasma concentration of >1.07 ng/mL was required to provide analgesia. Plasma concentrations were measured in additional cats after intranasal or oral dosing (2 microg/kg) and after 30 microg/kg in PLO gel. After oral and nasal dosing, Cmax values were 0.96 and 1.48 ng/mL at 5 and 2 min, respectively. Plasma fentanyl was not detected after application of the higher dose of fentanyl in PLO.  相似文献   

18.
The aim of this study was to evaluate the effect of opioid exposure on CXC chemokine ligand (CXCL)-8 production in cats using whole blood culture. Morphine, buprenorphine, fentanyl, and saline control were administered intravenously to five cats and whole blood pathogen associated molecular pattern motif-induced CXCL-8 production capacity was evaluated. Morphine potentiated CXCL-8 production. To further characterize this effect of morphine, morphine was incubated with whole blood ex vivo and pathogen associated molecular pattern motif-induced CXCL-8 production capacity was measured. There was a time and concentration dependent effect on CXCL-8 production, suggesting the proinflammatory effect of morphine is at least partially mediated by direct stimulatory effects on leukocytes. Additional investigation is indicated to assess the implications of the immunomodulatory actions of opioids in cats.  相似文献   

19.
Objective: To describe the clinical manifestations and response to management of opioid dysphoria in 3 dogs. Case summary: Three dogs being managed for post‐operative pain were evaluated. All 3 dogs had been managed with various opioids including morphine, hydromorphone, and fentanyl following the surgical procedure. The 3 dogs exhibited vocalization that did not respond to interaction and did not change with administration of analgesic and anxiolytic agents. The dogs were treated with naloxone and, within 5 minutes of its administration, ceased vocalizing, and became aware and interactive with their environment. Further pain management consisted of non‐steroidal anti‐inflammatory medications, alpha‐2 (α2) receptor agonists or the partial μ‐receptor opioid agonist, buprenorphine. New and unique information provided: Vocalization and lack of response to interaction with humans are clinical signs which can be seen in dogs with opioid dysphoria, and generally are not responsive to analgesics or sedation. Reversal with naloxone results in rapid resolution of vocalization and opioid‐induced dysphoria.  相似文献   

20.
ObjectiveTo determine the dose of naltrexone necessary to fully antagonize a high dose of remifentanil in cats.Study designProspective experimental study.AnimalsSix healthy adult cats weighing 4.9 ± 0.7 kg.MethodsIn a first phase, remifentanil (200 μg kg?1 followed by 60 μg kg?1 minute?1) was administered intravenously to two cats, causing an increase in locomotor activity. Naltrexone (100 μg kg?1) was then administered intravenously every minute until the increase in locomotor activity had been reversed. In a second phase, six cats were used. Baseline thermal threshold was determined, naltrexone (600 μg kg?1) was administered intravenously and 30 minutes later thermal threshold determination repeated. Remifentanil (200 μg kg?1 followed by 60 μg kg?1 minute?1) was administered intravenously and thermal threshold determination repeated at 60, 120, 180, and/or 240 minutes after naltrexone administration. Thermal threshold determinations were started shortly after the start of the continuous rate infusion (CRI) of remifentanil and this CRI was discontinued immediately after thermal threshold determination. If an increase in thermal threshold was found, naltrexone administration was repeated at decreasing intervals in the next experiment (all cats were not used for all dosing intervals). Experiments were repeated until a naltrexone dosing interval was found that prevented increases in thermal threshold for 4 hours in all six cats.ResultsIn the first phase, both cats became severely dysphoric following remifentanil administration. A cumulative naltrexone dose of 300 μg kg?1 was necessary to restore normal behavior in both cats. In the second phase, hourly administration of naltrexone (600 μg kg?1) prevented increases in thermal threshold associated with hourly administration of remifentanil for 4 hours. Less frequent administration did not prevent increases in thermal threshold consistently.ConclusionsHourly administration of naltrexone (600 μg kg?1) antagonizes the behavioral and antinociceptive effects of a high dose of remifentanil in cats.Clinical relevanceNaltrexone may be useful for the treatment of opioid overdose in cats.  相似文献   

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