Pharmacokinetics of the injectable formulation of methadone hydrochloride administered orally in horses.

Methadone hydrochloride is a synthetic mu-opioid receptor agonist with potent analgesic properties. Oral methadone has been successfully used in human medicine and may overcome some limitations of other analgesics in equine species for producing analgesia with minimal adverse effects. However, there are no studies describing the pharmacokinetics (PK) of oral opioids in horses. The aim of this study was to describe the PK of orally administered methadone (0.1, 0.2 and 0.4 mg/kg) and physical effects in 12 healthy adult horses. Serum methadone concentrations were measured by gas chromatography/mass spectrometry at predetermined time points for 24 h, and PK parameters were estimated using a noncompartmental model. Physical effects were observed and recorded by experienced clinicians. No drug toxicity, behavioural or adverse effects were observed in the horses. The disposition of methadone followed first order elimination and a biphasic serum profile with rapid absorption and elimination phases. The PK profile of methadone was characterized by high clearance (Cl/F), small volume of distribution (V(d)/F) and short elimination half-life (t(1/2)). The mean of the estimated t(1/2) (SD) for each dose (0.1, 0.2 and 0.4 mg/kg) was 2.2 (35.6), 1.3 (46.1) and 1.5 (40.8), and the mean for the estimated C(max) (SD) was 33.9 (6.7), 127.9 (36.0) and 193.5 (65.8) respectively.

Evaluation of the analgesic effects of epidurally administered morphine, alfentanil, butorphanol, tramadol, and U50488H in horses.

OBJECTIVE: To evaluate and compare effects of epidurally administered morphine, alfentanil, butorphanol, tramadol, and U50488H on avoidance threshold to noxious electrical stimulation over the dermatomes of the perineal, sacral, lumbar, and thoracic regions in horses. ANIMALS: 5 healthy adult horses. PROCEDURE: Using a Latin square complete repeated-measures design, horses were randomly assigned to receive 1 of 6 treatments (morphine, alfentanil, butorphanol, tramadol, U50488H, or sterile water) at intervals of at least 7 days. Agents were injected epidurally at the first intercoccygeal epidural space, and electrical stimulation was applied at repeated intervals for 24 hours to the dermatomes of the perineal, sacral, lumbar, and thoracic regions. Avoidance threshold to electrical stimulation was recorded. RESULTS: Administration of butorphanol, U50488H, and sterile water did not induce change in avoidance threshold. Alfentanil increased avoidance threshold during the first 4 hours, but not significantly. Tramadol and morphine significantly increased threshold and analgesic effects. Complete analgesia (avoidance threshold, >40 V) in the perineal and sacral areas was achieved 30 minutes after tramadol injection, compared with 6 hours after morphine injection. Duration of complete analgesia was 4 hours and 5 hours after tramadol and morphine injections, respectively. CONCLUSIONS AND CLINICAL RELEVANCE: Epidural administration of tramadol and morphine induces long-lasting analgesia in healthy adult horses. Epidural administration of opioids may provide long-lasting analgesia in horses without excitation of the CNS.

Effects of lumbosacral subarachnoid catheterization in horses.

OBJECTIVES: To evaluate the effects of long duration subarachnoid catheterization in horses on cerebrospinal fluid (CSF) cellularity and bacteriology, arterial blood pressure, heart rate, respiratory rate, rectal body temperature, and spontaneous locomotor activity. STUDY DESIGN: Prospective experimental study. ANIMAL: Five clinically normal healthy adults horses weighing 511 +/- 47 kg. METHODS: Subarachnoid catheters were placed using sedation and local anesthesia and maintained for 48 hours in standing horses. Cerebrospinal fluid samples were tested for cellularity and bacteria growth. Heart rate, respiratory rate, arterial blood pressure, and body temperature were recorded. Locomotor activity was graded. One-way repeated measures ANOVA and Bonferroni's test were used to statistically compare data from baseline to 12, 24, and 48 hours. RESULTS: Subarachnoid catheterization in horses produced an acute inflammatory reaction after 12 hours of catheterization, as evidenced by a statistically significant increase in CSF white blood cell count. No bacterial contamination was encountered. No significant differences were found in heart rate, respiratory rate, body temperature, and arterial blood pressure. The horses did not develop motor ataxia or proprioceptive deficits during 48 hours of catheterization. CONCLUSIONS: Results of this study suggest that 48 hours of subarachnoid catheterization in horses does not produce clinical signs of neurologic dysfunction or cardiovascular and respiratory changes, even though an inflammatory reaction occurred. CLINICAL RELEVANCE: Subarachnoid catheterization in horses is preferred for monitoring CSF pressure or for repeated collection. Understanding the effects of catheterization alone, allows the clinician to better interpret abnormalities in CSF collected.

Analgesia epidural com clonidina ou romifidina em cães submetidos à cirurgia coxofemoral / Epidural analgesia with clonidine or romifidine in dogs submitted to coxofemoral surgery

Avaliaram-se as alterações cardiorrespiratórias e a analgesia da administração epidural de clonidina ou romifidina em cães submetidos à cirurgia coxofemural. Foram utilizados 14 cães distribuídos em dois grupos: o grupo Cloni recebeu 150µg de clonidina e o grupo Romi, 20µg/kg de romifidina. A indução anestésica foi realizada com propofol e a anestesia cirúrgica mantida com halotano e O2 em respiração espontânea. A punção do espaço epidural foi feita logo após a indução. Antes da indução e a cada 10 minutos foram avaliadas as freqüências cardíaca e respiratória, a pressão arterial sistólica, a saturação de oxigênio da hemoglobina e a concentração de halotano. Após indução e ao término do procedimento cirúrgico coletou-se sangue arterial para avaliação gasométrica de pH, PaCO2, PaO2, SaO2, BE e HCO3-. Foi realizada avaliação pós-operatória do grau de analgesia (intensa, pouco intensa e inadequada) nas primeiras duas horas após término da cirurgia. Os animais do grupo Romi apresentaram bradicardia, bradiarritmias e hipertensão. A freqüência cardíaca e a pressão arterial sistólica no grupo Cloni mantiveram-se dentro da faixa de variação fisiológica para a espécie. A analgesia trans-operatória foi considerada intensa nos dois grupos. A administração epidural de clonidina ou romifidina produziu intensa analgesia transcirúrgica sem depressão respiratória e pouco intensa analgesia pós-operatória por duas horas.

Emergências em anestesia veterinária / Emergencies in veterinary anaesthesia

Emergências em anestesia veterinária geralmente säo acompanhadas de complicaçöes, uma vez que o médico-veterinário na maioria das vezes näo conta com meios para monitorizaçäo do paciente, como gasometria sangüínea, monitores cardíacos e ventilômetros. Dessa forma, em Medicina Veterinária deve-se lançar mäo de técnicas anestésicas que forneçam ao paciente adequado fluxo de oxigênio e estabilidade cardiocirculatória além de se contar com drogas para uso em emergências cardiopulmonares

Sedaçäo e analgesia com detomidina para diferentes procedimentos cirúrgicos em eqüinos / Allaying and analgesia with detomidine to different surgical proceedings in equines

Foi realizado um estudo para a determinaçäo das médias de dose (mcg/kg), tempo de latência, tempo de analgesia e tempo de recuperaçäo de eqüinos submetidos a diferentes procedimentos cirúrgicos, sob a açäo da detomidina pura. nas doses de 38,2 a 56,2 mcg/kg, a detomidina mostrou-se eficiente para a realizaçäo de cirurgias de pequeno e médio porte em eqüinos

Anestesia geral intravenosa em caninos com a associaçäo etomidato e fentanil / General intravenous anesthesia in dogs with association of etomidate and fentanyl

A associaçäo do hipno-indutor etomidato com o analgésico narcótico fentanil foi avaliada experimental e clinicamente em 20 animais nas doses de 1-2 mg/kg e 25-70mcg/kg. Ocorreram alteraçöes significativas nas freqüências cardíaca e respiratória, com os dados obtidos mantendo-se aceitáveis para a espécie canina. A associaçäo mostrou-se eficiente para a obtençäo de anestesia geral intravenosa em caninos.