Newer analgesics. Nonsteroid anti-inflammatory drugs, opioids, and combinations

Antinociceptive effects of tramadol and acepromazine in cats

Effects of tramadol and acepromazine on pressure and thermal thresholds were examined in eight cats. After baseline measurements, subcutaneous (SC) tramadol 1 mg/kg, acepromazine 0.1 mg/kg, tramadol 1 mg/kg with acepromazine 0.1 mg/kg, or saline 0.3 ml were given. Serial measurements were made for 24 h. Mean thermal thresholds did not change significantly [analysis of variance (ANOVA)] from baseline. The maximum thermal threshold increase above baseline was 2.8+/-2.8 degrees C at 6 h (P>0.05) after tramadol; it was above the 95% confidence interval (CI) at 0.75, 3 and 6 h. Pressure thresholds increased above baseline from 0.25 to 2 h after acepromazine (P<0.05) and from 0.5 to 3 h after the combination (P<0.05), with a maximum increase of 132+/-156 mmHg 0.25 h after acepromazine and 197+/-129 mmHg 0.5 h after the combination. Pressure thresholds were above the 95% CI from 0.25 to 2 h after acepromazine and from 0.5 to 3 h after the combination. SC tramadol at 1 mg/kg in cats had limited effect on thermal and pressure nociception, but this was enhanced by acepromazine. Acepromazine alone had pressure antinociceptive effects.

Comparison between analgesic effects of buprenorphine, carprofen, and buprenorphine with carprofen for canine ovariohysterectomy

OBJECTIVE

To compare the analgesic effects of buprenorphine, carprofen, and their combination in dogs undergoing ovariohysterectomy.

STUDY DESIGN

Prospective, randomized blinded clinical study.

ANIMALS

60 dogs.

METHODS

Treatments were buprenorphine 0.02 mg kg(-1), intramuscularly (IM) (group B); carprofen 4 mg kg(-1), subcutaneously (SC) (group C); or a combination of both (group CB). Anesthesia was induced with propofol and maintained with isoflurane. A Dynamic Interactive Visual Analog Scale (DIVAS, 0-100 mm) and the Glasgow Composite Pain Scale (GCMPS, 0-24) were used to evaluate comfort and sedation at baseline, 2, 4, 6, and 24 hours after extubation. Rescue analgesia was provided with buprenorphine (0.02 mg kg(-1)). Wound swelling measurements (WM) and a visual inflammation score (VIS) of the incision were made after surgery and 2, 4, 6, and 24 hours later. p < 0.05 was considered significant.

RESULTS

Group C required more propofol (5.0 +/- 1.4 mg kg(-1)) compared with B (3.3 +/- 1.1 mg kg(-1)) and CB (3.2 +/- 0.7 mg kg(-1)); respectively, p = 0.0002 and 0.0001. Rescue analgesia was required in nine dogs. B had a higher GCMPS and DIVAS III score at 6 hours (2.6 +/- 2.5) and (23 +/- 22.5 mm) compared with C (1.0 +/- 1.3, 6 +/- 7.3 mm) and CB (1.5 +/- 1.4, 8 +/- 10.7 mm); respectively, p = 0.02 and 0.006. Group C had a lower sedation score at 2 hours (43 +/- 23.6 mm) compared with B (68 +/- 32.1 mm) and BC (69 +/- 22.1 mm); respectively, p = 0.03 and 0.004. Group B had a higher WM score at 2 hours (3 +/- 0.8 mm) compared with C (2 +/- 0.6 mm) p = 0.01 and at 6 hours (3 +/- 1 mm) compared with C (2 +/- 0.8 mm) and CB (2 +/- 0.8 mm); respectively, p = 0.01 and 0.008. VIS was not different between groups.

CONCLUSION AND CLINICAL RELEVANCE

All treatments provided satisfactory analgesia for the first 6 hours and at 24 hours. C and CB pain score and WS were superior to B at 6 hours. No superior analgesic effect was noted when the drugs were combined.

Recent developments in nonsteroidal antiinflammatory drugs in cats

Pain, particularly chronic pain, is an underestimated ailment in cats. Veterinarians tend to under-diagnose and under-treat pain in this aloof and stoic species. Until recently, there was only one analgesic (i.e., butorphanol) approved in the United States for use in cats; but many analgesics, particularly opioids, have been used extra-label for this purpose. Nonsteroidal antiinflammatory drugs (NSAIDs) have been used sparingly in cats because of safety concerns, which are less of an issue with the newer agents. Meloxicam is the only NSAID labeled for use in cats in the United States, but other agents are available in this country and are labeled for use in cats in other countries.

Endoscopia gastroduodenal após administração de nimesulida, monofenilbutazona e meloxicam em cães

Avaliaram-se os aspectos da mucosa gastroduodenal em cães tratados experimentalmente com nimesulida, monofenilbutazona e meloxicam. Foram formados quatro grupos com oito cães. Os grupos 1, 2 e 3 receberam, respectivamente, tratamento com nimesulida, monofenilbutazona e meloxicam durante 21 dias, e o grupo 4 foi utilizado como controle. Todos os animais foram avaliados por exames endoscópicos do estômago e duodeno antes do experimento e aos 10 e 21 dias de tratamento. Os cães não manifestaram qualquer alteração clínica ou laboratorial durante o período de estudo. A avaliação endoscópica da mucosa gastroduodenal apresentou apenas lesões consideradas de baixo grau. Esses antiinflamatórios mostraram-se seguros para o trato gastrintestinal de cães clinicamente saudáveis.

GW406381, a novel COX-2 inhibitor, attenuates spontaneous ectopic discharge in sural nerves of rats following chronic constriction injury

There are several lines of evidence to suggest that cyclooxygenase-2 (COX-2) plays an important role in the generation and maintenance of neuropathic pain states following peripheral nerve injury. However, COX-2 inhibitors are generally ineffective in reversing mechanical allodynia and hyperalgesia in models of neuropathic hypersensitivity. Here, we have investigated the effects of GW406381, a novel COX-2 inhibitor, on mechanical allodynia, hyperalgesia and generation of spontaneous ectopic discharge in rats following chronic constriction injury (CCI) of the sciatic nerve and compared it with rofecoxib. GW406381 (5mg/kg, 5 days of treatment) significantly reversed the CCI-induced decrease in paw withdrawal thresholds (PWTs), assessed using both von Frey hair and paw pressure tests, whereas an equi-effective dose of rofecoxib (5mg/kg, 5 days of treatment) in inflammatory pain models was ineffective. In rats treated with GW406381, the proportion of fibres showing spontaneous activity was significantly lower (15.58%) than that in the vehicle (32.67%)- and rofecoxib (39.66%)-treated rats. Ibuprofen, a non-selective COX inhibitor, at 5mg/kg, orally dosed three times a day for 5 days did not significantly affect the PWTs in CCI rats. In naïve rats, GW406381 did not significantly change the PWTs. These results illustrate that COX-2 may indeed play an important role in the maintenance of neuropathic pain following nerve injury, but that only certain COX-2 inhibitors, such as GW406381, are effective in this paradigm. Whilst the mechanisms underlying this differential effect of GW406381 are not clear, differences in drug/enzyme kinetic interactions may be a key contributing factor.

Plasma concentrations of 13,14-dihydro-15-keto prostaglandin F2-alpha (PGFM), progesterone and estradiol in pregnant and nonpregnant diestrus cross-bred bitches

The canine corpus luteum (CL) typically sustains elevated plasma progesterone concentrations for 2 months or more, with a peak approximately 15-25 days after ovulation, followed by a slow decline. The processes involved in the slow, protracted regression of the CL over the remaining 1.5-2-month period in nonpregnant bitches and until shortly prepartum in pregnant bitches are not well characterized. The rapid luteolysis that occurs immediately prepartum appears to be a result of a prepartum rise in peripheral PGF. The potential role of PGF in the slow regression process in the several weeks preceding parturition and in nonpregnant bitches after 15-25 days after ovulation is not known. Therefore, plasma concentrations of 13,14-dihydro-15-keto-prostaglandin F2-alpha (PGFM), progesterone (P4) and estradiol (E2) were determined and compared in bitches during nonpregnant diestrus (n = 9) or pregnancy (n = 8). During the gradual decrease in plasma concentrations of progesterone in both groups, the P4 pattern appeared unrelated to changes in either E2 or PGFM concentrations. The PGFM pattern was different between diestrus and pregnant bitches (P > 0.01); there was an apparent progressive but slow increase in PGFM in pregnant bitches from Days 30 to 60, followed by a large increase prior to parturition; concentrations declined immediately postpartum. However, there were no increases in PGFM during the same interval in nonpregnant bitches. Mean estradiol concentrations were sporadically elevated during the last third of pregnancy and less so in nonpregnant diestrus; there was no acute prepartum increase in estradiol associated with the PGFM increase. In summary, although there were no apparent changes in peripheral PGF2alpha concentration involved in regulating the slow protracted phase of luteal regression in nonpregnant bitches, modest increases in PGFM may play a role in ovarian function after mid-gestation in pregnant bitches. Furthermore, the acute prepartum rise in PGFM was not dependent on any concomitant increase in estradiol concentrations.

Cardiopulmonary effects of sufentanil long acting on sevoflurane anaesthesia in dogs

OBJECTIVE

To evaluate the cardiopulmonary effects of sufentanil long acting (SLA) in sevoflurane-anaesthetized dogs.

STUDY DESIGN

Randomized prospective study. Animals Forty female dogs (beagles) aged 1-2 years, weighing 11.97 +/- 1.40 kg.

MATERIALS AND METHODS

The dogs were divided into five groups of eight. Two control groups were used: group A received intramuscular (IM), SLA (50 microg kg(-1)) alone, while group B received the SLA vehicle followed by sevoflurane anaesthesia for 90 minutes. In the other groups, SLA (50 microg kg(-1) IM) was given immediately before (group C(0)), 15 minutes before (group D(15)) or 30 minutes (group E(30)) before induction [with intravenous (IV) thiopental] of sevoflurane anaesthesia lasting for 90 minutes. Heart rate, arterial blood pressure, respiratory rate (f(r)), arterial oxygen haemoglobin saturation and end-tidal sevoflurane concentration (Fe'SEVO) were measured every 10 minutes during anaesthesia and at 2, 4 and 24 hours after induction (not Fe'SEVO). Acid-base and blood gas analyses were performed.

RESULTS

Sufentanil LA reduced heart rate and increased arterial CO(2) tensions during anaesthesia. Respiratory depression was least in group E(30) compared with groups C(0) and D(15). Bradycardia was present for at least 24 hours. Respiratory rate was least in group B although arterial O(2) and CO(2) tension values were acceptable up to 24 hours after anaesthesia.

CONCLUSIONS

Pre-anaesthetic medication with SLA moderately aggravated the cardiopulmonary effects of sevoflurane.

CLINICAL RELEVANCE

In spite of a moderate depressant effect on cardiorespiratory parameters, SLA may be of use as pre-anaesthetic medication before sevoflurane anaesthesia in dogs. Intermittent positive pressure ventilation may occasionally be necessary.

Analgesic Comparison of Meloxicam or Ketoprofen for Orthopedic Surgery in Dogs

OBJECTIVE

To compare the safety and efficacy of 2 analgesic protocols (preoperative meloxicam or intraoperative ketoprofen administration) during the first 24 hours after orthopedic surgery in dogs.

STUDY DESIGN

Double-blind, prospective randomized clinical trial.

ANIMALS

Sixty client-owned dogs.

METHODS

Dogs with surgical orthopedic disorders were randomly separated into 2 groups: 30 dogs were administered 0.2 mg/kg meloxicam intravenously (IV) immediately before induction and 30 dogs were administered 2 mg/kg ketoprofen IV, 30 minutes before the end of surgery. Pain was assessed with a visual analog scale (VAS) and a cumulative pain score (CPS) preoperatively and at 30 minutes, 1, 2, 3, 4, 6, 8, and 24 hours after extubation. Selected serum biochemical variables were measured before and 24 hours after surgery and, buccal mucosal bleeding time (BMBT) and whole blood clotting time (WBCT) were measured before and 8 hours after surgery. Dogs were anesthetized with propofol and maintained on halothane in oxygen. Any complications were documented for 7 days after surgery. Results were compared between the 2 groups for significant differences in VAS scores (2-sample t-test) and in CPS (Wilcoxon's 2-sample test). Moreover, results were analyzed for significant differences in area under the curve (AUC) for VAS (2-sample t-test) and CPS (Wilcoxon's 2-sample test) among groups. To assess the effects of treatments on biochemical and coagulation functions, pre- and postoperative mean values of BMBT and WBCT were compared within both treatment groups (paired t-tests) and between both groups (2-sample t-test).

RESULTS

No significant differences in pain response or coagulation were found between meloxicam- and ketoprofen-treated dogs. In both groups, alkaline phosphatase and alanine aminotransferase concentrations were significantly increased compared with baseline. No serious complications occurred.

CONCLUSIONS

Preoperative administration of meloxicam is a safe and effective method of controlling postoperative pain for up to 24 hours in dogs undergoing orthopedic surgery.

CLINICAL RELEVANCE

Analgesia after administration of preoperative meloxicam was comparable with administration of ketoprofen at the end of the surgery.

Pain management in cats--past, present and future. Part 2. Treatment of pain--clinical pharmacology

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.

Feline perioperative pain management

Veterinary surgeons today are performing increasingly complex and invasive feline surgical procedures. In light of this, it is crucial that perioperative pain management in these patients be a top priority. This article outlines pain physiology and pathophysiology, pain recognition and management strategies, relevant pharmacology, and techniques for local and regional analgesia in cats.

Cyclooxygenase selectivity of nonsteroidal anti-inflammatory drugs in canine blood

OBJECTIVE

To evaluate cyclooxygenase (COX) selectivity of several nonsteroidal anti-inflammatory drugs (NSAID) in canine blood in vitro.

ANIMALS

11 healthy adult male hound crosses.

PROCEDURE

9 NSAID were studied at 5 concentrations. Thromboxane B2 (TxB2) was assayed as a measure of COX-1 activity in clotted blood. Prostaglandin E2 (PGE2) was assayed as a measure of COX-2 activity in heparinized, lipopolysaccharide (LPS)-stimulated blood. All assays were competitive ELISA tests. Cyclooxygenase selectivity was expressed as a ratio of the concentration of an NSAID that inhibited 50% of the activity (IC50) of COX-1 to the IC50 of COX-2. A separate ratio of the concentration that inhibited 80% of COX activity (IC80) was also determined. A ratio of < 1.0 indicated selectivity for COX-1, whereas a ratio of > 1.0 indicated COX-2 selectivity.

RESULTS

Ketoprofen, aspirin, and etodolac were COX-1 selective. Piroxicam, meloxicam, and carprofen had COX-2 selectivity. The IC50 and IC80 values were similar for most NSAID.

CONCLUSIONS

This methodology provides repeatable data from individual dogs and is comparable to results of previous in vitro and ex vivo models. Findings are also consistent with those of canine studies performed in vivo, suggesting that this is a viable in vitro assessment of the COX selectivity of NSAID in dogs.

Avian analgesia

Understanding behavioral indicators of pain and other assessment techniques can help one to recognize pain in birds and prompt us to treat birds with analgesics. An analgesic plan needs to include several modalities to help reduce pain in the avian patient. Analgesic therapy should be directed at treating the disease/injury in the periphery, and the changes that occur in the central nervous system (CNS). Both opioid and nonsteroidal anti-inflammatory drug (NSAID) therapeutics can be selected to provide analgesia for the avian patient.

Nonsteroidal anti-inflammatory analgesics. Indications and contraindications for pain management in dogs and cats

Nonsteroidal anti-inflammatory analgesics (NSAIAs) are effective in controlling most acute and chronic pain conditions. In veterinary practice these analgesics may be superior to opioids in that the duration of action is much longer, with equal efficacy in many instances, making effective pain management possible for most veterinary patients. NSAIAs act synergistically in combination with other modalities of pain management, including all opioids, local anesthetics, and various sedatives. Because of their mechanism of action, however, there is a potential for perturbation of several homeostatic functions mediated by prostaglandins. Not all NSAIAs are equal in efficacy and safety, so careful patient and NSAIA selection with appropriate monitoring is advised. This article discusses the indications and contraindications for NSAIA use with a short description of the currently available NSAIAs approved for use in veterinary patients.

Postoperative management of the emergency surgery small animal patient

Hypovolemia, hypothermia, and hypotension are common postoperative findings that predispose the critically ill patient to secondary complications. This patient population is especially vulnerable to sepsis, hypoxia, and immune dysfunction. Careful monitoring is essential for early recognition of potentially life-threatening physiologic derangements. Early and aggressive intervention may help minimize systemic insult before it progresses to acute respiratory distress syndrome, acute renal failure, disseminated intravascular coagulation, or multiple organ failure.