Effects of hydromorphone or oxymorphone, with or without acepromazine, on preanesthetic sedation, physiologic values, and histamine release in dogs

Intramuscular alfaxalone with or without buprenorphine or hydromorphone provides sedation with minimal adverse effects in healthy rabbits (Oryctolagus cuniculus) in a randomized blinded controlled trial

OBJECTIVE

To evaluate the effects of alfaxalone administered IM with or without buprenorphine or hydromorphone in healthy rabbits (Oryctolagus cuniculus).

ANIMALS

24 male rabbits undergoing elective orchiectomy between August 21, 2021, and November 6, 2021.

PROCEDURES

In this controlled clinical trial, rabbits were randomly assigned to receive alfaxalone (4 mg/kg, IM) alone (group A; n = 8) or with buprenorphine (0.03 mg/kg, IM; group BA; 8) or hydromorphone (0.1 mg/kg, IM; group HA; 8). Vital signs and sedation scores were recorded immediately prior to (T0) and 10 minutes after (T1) treatment. Ease of IV catheter placement and pain scores were also evaluated. All rabbits received ketamine (2.5 mg/kg, IV), midazolam (0.13 mg/kg, IV), and meloxicam (0.5 mg/kg, SC) before orchiectomy but after IM treatments. Results were compared across groups with ANOVA or Fisher exact tests and across time with paired t tests.

RESULTS

Sedation score, median time to recumbency, and ease of catheter placement did not differ among groups. Supraglottic airway device placement was possible for 1 rabbit in group A, 1 in group BA, and 2 in group HA. Mean respiratory rate at T1 versus T0 was significantly decreased for groups BA (63.8 vs 128.6 breaths/min) and HA (66.7 vs 123.2 breaths/min). Mean postoperative pain scores were significantly lower for rabbits in group HA (0.58), compared with those in groups A (2.25) and BA (2.06).

CLINICAL RELEVANCE

All 3 treatments provided reliable sedation; however, alfaxalone (4 mg/kg, IM) combined with hydromorphone (0.1 mg/kg, IM) may be a better choice for painful procedures.

A preliminary study comparing the sedative, cardiorespiratory, and histaminic-releasing effects of intramuscular and intravenous administration of pethidine (meperidine) with midazolam in healthy cats

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First reporting of the sedative quality of pethidine in combination with midazolam in healthy cat.

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Intravenous injection of pethidine-midazolam was associated with transient elevation of plasma histamine concentration but self-limiting in healthy cat.

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The pethidine-midazolam can provide short duration of sedation without obvious side effects in healthy cat.

Pethidine is a synthetic opioid that is widely used in cats. However, the sedative, cardiorespiratory, and histaminic effects following administration of pethidine with midazolam in cats remain unclear. The objectives of this study were to evaluate and compare changes before and after intravenous (IV) and intramuscular (IM) administration of pethidine with midazolam in healthy cats. In this prospective randomized blind study, 12 cats were assigned equally to either the IV or IM treatment group. The IV group received pethidine 3 mg/kg and midazolam 0.1 mg/kg. The IM group received pethidine 6 mg/kg and midazolam 0.2 mg/kg. The sedative effects, heart rate, respiratory rate, non-invasive arterial blood pressures, and behavioral signs were recorded before and at 2, 5, 15, 30, 45, and 60 min after the injection. Blood samples were taken for an ELISA histamine assay at baseline and at 5 and 15 min after treatment. Cats that received IV treatment were rapidly induced a moderate degree of sedation but those received IM treatment were only mildly sedated. There was no significant difference in the cardiorespiratory values within and between the treatments over time. Plasma histamine concentrations increased by 3 and 5 times at 5 and 15 min after IV treatment, respectively, compared to baseline values. IM injections induced minimal changes in the plasma histamine concentration. In summary, intravenous pethidine with midazolam induced potentially superior sedative effects without serious side effects in clinically healthy cats. However, further studies with larger sample sizes are required to validate this finding.

Hemodynamic Effects of Different Combinations of Midazolam and Opioids in Healthy Dogs

The purpose of this study was to compare the hemodynamic effects of four different combinations of midazolam and opioids in healthy dogs. Twenty-four healthy dogs were divided in four groups (n = 6) using intramuscular midazolam 0.3 mg/kg and morphine 0.3 mg/kg (G_MOR), methadone 0.3 mg/kg (G_MET), butorphanol 0.2 mg/kg (G_BUT) or fentanyl 5 ug/kg (G_FEN). Cardiovascular variables were recorded before (T_B) and 20 minutes following drug administration (T₂₀) and comprised arterial blood pressure, heart rate and cardiac index. Subsequently, left ventricular work index and total peripheral resistance index were calculated using the previous variables. At the end of the study, data were compared using analysis of variance followed by Tukey test and Friedman followed by Dunn test, all under 5% significance. No differences were found on cardiovascular variables at all times among the groups, which indicates that all combinations provide hemodynamic stability for clinical sedation of healthy dogs. However, a few animals showed paradoxical excitation in G_BUT. In conclusion, the association of midazolam with morphine, methadone, butorphanol or fentanyl provides cardiovascular stability and can be used to sedate dogs undergoing cardiovascular examination, although caution is warranted with the use of midazolam with butorphanol due to possible paradoxical excitation.

Conventional and advanced echocardiographic assessment of systolic function in dogs sedated with dexmedetomidine or acepromazine

Dexmedetomidine and acepromazine, sedatives commonly used in dogs have opposite vascular effects, resulting in afterload increase and decrease, respectively. This could variably affect systolic myocardial function. Previous echocardiographic studies assessing the cardiovascular effects of these drugs used conventional echocardiography, while advanced techniques such as speckle tracking echocardiography (STE) and tissue Doppler imaging (TDI), which are known to provide a more accurate assessment of systolic function, have been rarely used for this aim. Moreover, in the few studies using advanced techniques, the drugs where combined with opioids. Therefore, the main objective of this prospective study was to assess systolic myocardial function by conventional and advanced echocardiography (STE and TDI), in dogs sedated exclusively with dexmedetomidine or acepromazine not combined with other drugs. Twenty healthy dogs were randomly divided into two groups, Group A (acepromazine, 20 μg/kg IM), and Group D (dexmedetomidine, 5 μg/kg IM), cardiovascular parameters were assessed before sedation (T0), and thirty minutes afterwards (T1). Systolic arterial pressure and heart rate decreased in both groups at T1 as compared to T0. Only one conventional echocardiographic raw variable (left ventricular internal dimension in systole) and three out of five advanced echocardiographic variables (radial TDI systolic velocities at the epicardial region of the left ventricular free wall, longitudinal TDI systolic velocities of the septal mitral valve annulus and the STE-derived left ventricular global strain), were affected in Group D. A systolic impairment was observed in Group D and better estimated by advanced echocardiography. In Group A, only the end diastolic voume index (conventional echocardiography) was decreased. Both protocols seem to induce echocardiographic changes more likely secondary to their vascular action.

Effects of perioperative saphenous and sciatic nerve blocks, lumbosacral epidural or morphine-lidocaine-ketamine infusion on postoperative pain and sedation in dogs undergoing tibial plateau leveling osteotomy

OBJECTIVE

To compare the quality of postoperative analgesia and sedation after preoperative saphenous and sciatic nerve blockade, preoperative lumbosacral epidural injection and perioperative intravenous (IV) morphine, lidocaine and ketamine infusions in dogs undergoing stifle arthroscopy and tibial plateau leveling osteotomy (TPLO) under general anesthesia.

STUDY DESIGN

Prospective, blinded, randomized, clinical comparison study.

ANIMALS

A total of 45 dogs weighing 33.9 (15.9-56.7) kg and aged 5.2 (1.0-12.0) years, mean (range), undergoing elective unilateral TPLO for spontaneous cranial cruciate ligament rupture.

METHODS

Client-owned dogs were enrolled. Dogs were randomly assigned to one of three groups: group MLK, perioperative IV morphine, lidocaine and ketamine infusion; group EPID, lumbosacral epidural with ropivacaine and morphine; or group SSNB, saphenous and sciatic nerve blockade with ropivacaine. Routine stifle arthroscopy followed by TPLO surgery was performed. Sedation and pain scores were assessed at 0, 2, 4, 8 and 24 hours following extubation. Rescue analgesia was administered as prescribed by Glasgow composite pain score-short form score >5.

RESULTS

Sedation scores for MLK were higher than EPID and SSNB. Pain scores for SSNB were lower than those for EPID and MLK. No significant differences were found in anesthesia duration or surgery duration among groups. No dogs required rescue analgesia.

CONCLUSIONS AND CLINICAL RELEVANCE

Although analgesia was adequate in all groups, the best combination of analgesia without increased sedation was recorded for SSNB.

Pharmacokinetics of hydromorphone hydrochloride after intramuscular and intravenous administration of a single dose to orange-winged Amazon parrots (Amazona amazonica)

OBJECTIVE

To evaluate the pharmacokinetics of hydromorphone hydrochloride after IM and IV administration to orange-winged Amazon parrots (Amazona amazonica).

ANIMALS

8 orange-winged Amazon parrots (4 males and 4 females).

PROCEDURES

Hydromorphone (1 mg/kg) was administered once IM. Blood samples were collected 5 minutes and 0.5, 1.5, 2, 3, 6, and 9 hours after drug administration. Plasma hydromorphone concentrations were determined with liquid chromatography-tandem mass spectrometry, and pharmacokinetic parameters were calculated with a compartmental model. The experiment was repeated 1 month later with the same dose of hydromorphone administered IV.

RESULTS

Plasma hydromorphone concentrations were > 1 ng/mL for 6 hours in 8 of 8 and 6 of 7 parrots after IM and IV injection, respectively. After IM administration, mean bioavailability was 97.6%, and mean maximum plasma concentration was 179.1 ng/mL 17 minutes after injection. Mean volume of distribution and plasma drug clearance were 4.24 L/kg and 64.2 mL/min/kg, respectively, after IV administration. Mean elimination half-lives were 1.74 and 1.45 hours after IM and IV administration, respectively.

CONCLUSIONS AND CLINICAL RELEVANCE

Hydromorphone hydrochloride had high bioavailability and rapid elimination after IM administration, with rapid plasma clearance and a large volume of distribution after IV administration in orange-winged Amazon parrots. Drug elimination half-lives were short. Further pharmacokinetic studies of hydromorphone and its metabolites, including investigation of multiple doses, different routes of administration, and sustained-release formulations, are recommended.

Effect of Methadone or Hydromorphone on Cardiac Conductivity in Dogs Before and During Sevoflurane Anesthesia

Objective: To evaluate changes in electrocardiogram (ECG) variables in healthy dogs receiving either methadone or hydromorphone IV before and during sevoflurane anesthesia.

Study Design: Prospective clinical study.

Animals: Forty client-owned dogs.

Methods: Dogs were randomized to receive methadone 0.5 mg/kg IV or hydromorphone 0.1 mg/kg IV in each part of a two-part study. In part one, dogs received the opioid prior to sevoflurane anesthesia (groups MS, n = 12 and HS, n = 12). Anesthesia was induced with propofol IV, maintained with sevoflurane, and dogs were mechanically ventilated. Standard 6-lead ECG recordings were obtained before opioid administration, 2, 5, and 10 min after opioid administration prior to anesthesia, and during anesthesia 15 min after end-tidal sevoflurane stabilized at 2.4%. In part two, conscious dogs received the same opioid treatments and ECGs were obtained at equivalent time points without undergoing anesthesia (groups M, n = 8 and H, n = 8). Values for ECG variables were determined by a blinded cardiologist and included: Heart rate (HR), PR interval, QT interval, and HR corrected QT interval (QT_c) using the Bazett (QT_cB), Fridericia (QT_cF), and Van de Water (QT_cV) formulas. Differences over time and between all four groups were evaluated using ANOVA for repeated measures with significance set at p ≤ 0.05.

Results: Both methadone and hydromorphone administration reduced HR and prolonged PR and QT intervals, with greater changes observed during sevoflurane anesthesia. The greatest prolongation in QT interval was observed in dogs administered methadone during sevoflurane anesthesia.

Conclusions and Clinical Relevance: Methadone and hydromorphone caused disturbances in myocardial electrical activity, and the addition of sevoflurane enhanced these disturbances. Both drugs caused considerable QT interval prolongation into the proarrhythmogenic range, with methadone causing greater prolongation.

Effects of 2% lidocaine hydrochloride solution as a coinduction agent with propofol on cardiopulmonary variables and administered propofol doses in healthy dogs premedicated with hydromorphone hydrochloride and acepromazine maleate

OBJECTIVE

To evaluate the effects of lidocaine as a coinduction agent with propofol on cardiopulmonary variables and administered propofol doses in healthy dogs premedicated with hydromorphone hydrochloride and acepromazine maleate and anesthetized with isoflurane.

ANIMALS

40 client-owned dogs (American Society of Anesthesiologists physical status classification I or II and age ≥ 6 months) scheduled to undergo anesthesia for elective procedures.

PROCEDURES

In a randomized, blinded, controlled clinical trial, dogs received 2% lidocaine hydrochloride solution (2.0 mg/kg [0.9 mg/lb], IV; n = 20) or buffered crystalloid solution (0.1 mL/kg [0.05 mL/lb], IV; 20; control treatment) after premedication with acepromazine (0.005 mg/kg [0.002 mg/lb], IM) and hydromorphone (0.1 mg/kg, IM). Anesthesia was induced with propofol (1 mg/kg [0.45 mg/lb], IV, with additional doses administered as needed) and maintained with isoflurane. Sedation was assessed, and anesthetic and cardiopulmonary variables were measured at various points; values were compared between treatment groups.

RESULTS

Propofol doses, total sedation scores, and anesthetic and most cardiopulmonary measurements did not differ significantly between treatment groups over the monitoring period; only oxygen saturation as measured by pulse oximetry differed significantly (lower in the lidocaine group). Mean ± SD propofol dose required for endotracheal intubation was 1.30 ± 0.68 mg/kg (0.59 ± 0.31 mg/lb) and 1.41 ± 0.40 mg/kg (0.64 ± 0.18 mg/lb) for the lidocaine and control groups, respectively.

CONCLUSIONS AND CLINICAL RELEVANCE

No propofol-sparing effect was observed with administration of lidocaine as a coinduction agent for the premedicated dogs of this study. Mean propofol doses required for endotracheal intubation were considerably lower than currently recommended doses for premedicated dogs. (J Am Vet Med Assoc 2020;256:93-101).

Pharmacokinetics and pharmacodynamics of hydromorphone after intravenous and intramuscular administration in horses

OBJECTIVE

To compare the pharmacokinetics and pharmacodynamics of hydromorphone in horses after intravenous (IV) and intramuscular (IM) administration.

STUDY DESIGN

Randomized, masked, crossover design.

ANIMALS

A total of six adult horses weighing [mean ± standard deviation (SD))] 447 ± 61 kg.

METHODS

Horses were administered three treatments with a 7 day washout. Treatments were hydromorphone 0.04 mg kg^⁻1 IV with saline administered IM (H-IV), hydromorphone 0.04 mg kg^⁻1 IM with saline IV (H-IM), or saline IV and IM (P). Blood was collected for hydromorphone plasma concentration at multiple time points for 24 hours after treatments. Pharmacodynamic data were collected for 24 hours after treatments. Variables included thermal nociceptive threshold, heart rate (HR), respiratory frequency (f_R), rectal temperature, and fecal weight. Data were analyzed using mixed-effects linear models. A p value of less than 0.05 was considered statistically significant.

RESULTS

The mean ± SD hydromorphone terminal half-life (t_1/2), clearance and volume of distribution of H-IV were 19 ± 8 minutes, 79 ± 12.9 mL minute^⁻1 kg^⁻1 and 1125 ± 309 mL kg^⁻1. The t_1/2 was 26.7 ± 9.25 minutes for H-IM. Area under the curve was 518 ± 87.5 and 1128 ± 810 minute ng mL^⁻1 for H-IV and H-IM, respectively. The IM bioavailability was 217%. The overall thermal thresholds for both H-IV and H-IM were significantly greater than P (p < 0.0001 for both) and baseline (p = 0.006). There was no difference in thermal threshold between H-IV and H-IM. No difference was found in physical examination variables among groups or in comparison to baseline. Fecal weight was significantly less than P for H-IV and H-IM (p = 0.02).

CONCLUSIONS AND CLINICAL RELEVANCE

IM hydromorphone has high bioavailability and provides a similar degree of antinociception to IV administration. IM hydromorphone in horses provides a similar degree and duration of antinociception to IV administration.

Comparison of the sedative effects of medetomidine administered intranasally, by atomization or drops, and intramuscular injection in dogs

OBJECTIVE

To compare the sedative effects of intranasal atomization (IN_A) of medetomidine with intranasal drops (IN_D) and intramuscular (IM) injection in healthy dogs.

STUDY DESIGN

Prospective, blinded, randomized study.

ANIMALS

A group of 18 mixed-breed shelter-owned dogs weighing 27 ± 4.3 kg (mean ± standard deviation).

METHODS

The dogs were randomly assigned to equal groups of six dogs for administration of medetomidine (40 μg kg^-1) by IN_A, IN_D and IM routes. Ease of administration was evaluated using a resistance scale. Composite sedation score (CSS), heart rate (HR) and respiratory frequency (f_R) were measured immediately before (T0, baseline) and after drug administration at time points 15, 45, 75 and 120 minutes. The time of onset of sedation was recorded. Ease of administration and onset of sedation were analysed by the Kruskal-Wallis and post hoc Dunn's tests. Repeated measures analysis of anova and least significant difference tests were used to analyse CSS, HR and f_R over time. Tukey's post hoc test was used for time point comparisons among groups. Significance was set at p < 0.05.

RESULTS

No differences were detected among groups for ease of administration (p = 0.346). CSS increased in all groups from baseline values. Onset of sedation in IM was 6.3 ± 2.0 minutes, in IN_A was 7.2 ± 2.5 minutes and in IN_D was 20.7 ± 5.4 minutes. CSS in IN_D was lower than in the other groups at T15 and lower than in IN_A at T45. CSS was not different between IM and IN_A. HR and f_R decreased in all groups compared with respective baseline values. HR in IN_D was lower than in IM at T45-T120.

CONCLUSIONS AND CLINICAL RELEVANCE

IN_A medetomidine (40 μg kg^-1) can be an alternative and noninvasive route to IM injections for sedating healthy dogs. IN_D resulted in a slow onset of sedation.

Effect of preoperative hydromorphone in patients undergoing laparoscopic radical gastrectomy. A double-blind, randomized and controlled trial

Objectives:

To determine the efficacy of preemptive hydromorphone for laparoscopic radical gastrectomy.

Methods:

The present prospective and double-blinded study was performed in the The First Hospital, Jilin University, Changchun, China, between July 2017 and April 2018. Fifty patients scheduled for laparoscopic radical, gastrectomy were equally randomized into 2 groups, which were administrated different drugs 10 minutes before surgery. Group P (the preemptive hydromorphone group) was administrated 2 mg hydromorphone (2 mL), and Group C (the control group) was administrated 2 mL normal saline intravenously. A standardized general anesthesia were conducted. Blood pressure and heart rate, postoperative morphine consumption, pain intensity, sedation status, and side effects were recorded.

Results:

Group C had larger intraoperative hemodynamic changes, higher postoperative visual analogue scale score, more morphine consumption and lower overall satisfaction degree than Group P. No difference was found between the 2 groups in sedation status and adverse effects.

Conclusion:

Preoperative 2 mg hydromorphone could reduce intraoperative changes of blood pressure and heart rate, postoperative pain intensity, and morphine consumption without an increase of adverse effects.

The pharmacokinetics and pharmacodynamics of intravenous hydromorphone in horses

OBJECTIVE

Describe the pharmacokinetics and pharmacodynamics of intravenous hydromorphone in healthy horses.

STUDY DESIGN

Masked, randomized, cross-over, Latin square design.

ANIMALS

A group of eight healthy adult horses METHODS: Horses were administered each of four treatments with an 8 day washout. Treatments groups included intravenous hydromorphone 0.02 mg kg^-1 (LD), 0.04 mg kg^-1 (MD), 0.08 mg kg^-1 (HD) and saline (P). Blood samples for hydromorphone analysis were obtained for 24 hours after treatment. Plasma hydromorphone was quantified and pharmacokinetic parameters were determined using non-compartmental analysis. Pharmacodynamic data collected for 24 hours after treatment included thermal nociceptive threshold, heart rate (HR), respiratory rate (f_R) and rectal temperature, and analyzed using mixed-effects linear models.

RESULTS

Mean (± standard deviation) hydromorphone terminal half-life (t_1/2), systemic clearance and apparent volume of distribution at steady state (Vd_ss) were 18.1 ± 18.6, 34.0 ± 12.8, and 41.3 ± 32.5 minutes, 66.6 ± 5.3, 550.0 ± 76.4, and 92.7 ± 13.9 mL kg^-1 minute^-1, and 1118 ± 369, 1460 ± 325 and 2242 ± 950 mL kg^-1 for treatments LD, MD and HD, respectively. Thermal threshold increased significantly compared to baseline for all treatments for up to 12 hours. HR was elevated above baseline in treatments LD, MD and HD, extending to 30, 15 and 105 minutes after treatment, respectively. Respiratory rate was elevated above baseline in treatments MD and HD from 30 to 195 minutes and from 45 to 480 minutes after treatment, respectively. Temperature was elevated above baseline in treatment HD until 255 minutes after treatment.

CONCLUSIONS

Hydromorphone exhibited a short t_1/2, rapid clearance and large Vd_ss in horses. It also provided a dose-dependent increase in thermal threshold with associated increases in HR, f_R and rectal temperature.

CLINICAL RELEVANCE

Hydromorphone 0.04 mg kg^-1 provided clinically relevant thermal antinociception with minimal adverse effects.

Pharmacokinetics of intramuscular alfaxalone and its echocardiographic, cardiopulmonary and sedative effects in healthy dogs

The pharmacokinetics and the effects of a single intramuscular (IM) dose of alfaxalone on sedation and cardiopulmonary and echocardiographic variables was studied in dogs. Twelve healthy adult Beagles (3 females, 9 males) were used in this prospective controlled cross-over trial. Echocardiography was performed with and without 4 mg kg-1 alfaxalone IM with a week wash-out interval. Sedation (19-point scale; 0 = no sedation), cardiopulmonary parameters, blood gas analysis and plasma concentration of alfaxalone were assessed every 5 minutes following the injection (T0). The influence of the alfaxalone plasma concentration and time on physiological variables was tested using a linear model whereas echocardiographic measurements were compared between conscious and alfaxalone-administered dogs using paired t-tests. Compared to baseline, alfaxalone administration was followed by an increase in heart rate (HR) from T5 to T30 and a decrease in mean arterial pressure (MAP) at T10, T25 and T30, in stroke volume (SV; 15 ± 5 to 11 ± 3 ml; P<0.0001), and end-diastolic volume (EDV; 24.7 ± 5.7 to 19.4 ± 4.9 ml). Cardiac output (CO) and blood gas analysis did not change significantly throughout. Mean plasma half-life was 29 ± 8 minutes, volume of distribution was 1.94 ± 0.63 L kg-1, and plasma clearance was 47.7 ± 14.1 ml kg-1 minute-1. Moderate to deep sedation was observed from T5 to T35. Ten dogs showed paddling, trembling, nystagmus and strong reaction to sound during the procedure. Although there were no significant changes in CO and oxygenation, the impact of HR, MAP, SV, EDV alterations requires further investigations in dogs with cardiac disease.

Comparison of fentanyl and hydromorphone constant rate infusions for pain management in dogs in an intensive care unit

OBJECTIVE

To compare the efficacy and quality of analgesia provided by constant rate infusions (CRIs) of hydromorphone and fentanyl in dogs in the intensive care unit (ICU).

STUDY DESIGN

Prospective, randomized, blinded, clinical trial.

ANIMALS

A total of 29 client-owned dogs.

METHODS

Dogs prescribed a μ-opioid agonist infusion for postsurgical or medical pain were randomized to be administered either hydromorphone (0.025 or 0.05 mg kg^-1 bolus, followed by a 0.03 mg kg^-1 hour^-1 infusion) or fentanyl (2.5 or 5 μg kg^-1 bolus, followed by a 3 μg kg^-1 hour^-1 infusion). The technical staff and clinicians were blinded as to which drug was administered. Pain scores, using the Colorado State University Canine Acute Pain Scale, sedation scores and nausea scores were assigned at regular intervals and compared between groups. Dose escalation and de-escalation of the study drug were performed according to set protocols. Adverse clinical signs and all other medications administered were recorded and compared between groups. The study drug was discontinued if the animal remained painful despite dose escalations, or if adverse effects were noted.

RESULTS

The pain scores were of low magnitude and were not significantly different between groups. The use of concurrent analgesia, sedation/anxiolytic medications and antacid/antiemetic medications was not different between groups. Sedation and nausea scores were not statistically different between groups.

CONCLUSIONS AND CLINICAL RELEVANCE

Hydromorphone and fentanyl CRIs appear to be equally effective for adequate pain relief in dogs, with no significant differences in adverse effects. Therefore, either drug may be chosen for control of postsurgical or medical pain in an ICU setting.

The pharmacokinetics and analgesic effects of extended-release buprenorphine administered subcutaneously in healthy dogs

Buprenorphine is a partial μ agonist opioid used for analgesia in dogs. An extended-release formulation (ER-buprenorphine) has been shown to provide effective analgesia for 72 hr in rats and mice. Six healthy mongrel dogs were enrolled in a randomized, blinded crossover design to describe and compare the pharmacokinetics and pharmacodynamics of ER-buprenorphine administered subcutaneous at 0.2 mg/kg (ER-B) and commercially available buprenorphine for injection intravenously at 0.02 mg/kg (IV-B). After drug administration, serial blood samples were collected to measure plasma buprenorphine concentrations using liquid chromatography/mass spectrometry detection. Heart rate, respiratory rate, body temperature, sedation score, and thermal threshold latency were recorded throughout the study. Median (range) terminal half-life, time to maximum concentration, and maximum plasma concentration of ER-buprenorphine were 12.74 hr (10.43-18.84 hr), 8 hr (4-36 hr), and 5.00 ng/ml (4.29-10.98 ng/ml), respectively. Mild bradycardia, hypothermia, and inappetence were noted in both groups. Thermal threshold latency was significantly prolonged compared to baseline up to 12 hr and up to 72 hr in IV-B and ER-B, respectively. These results showed that ER-buprenorphine administered at a dose of 0.2 mg/kg resulted in prolonged and sustained plasma concentrations and antinociceptive effects up to 72 hr after drug administration.

Antihistaminic and cardiorespiratory effects of diphenhydramine hydrochloride in anesthetized dogs undergoing excision of mast cell tumors

OBJECTIVE To evaluate the effects of IV diphenhydramine hydrochloride administration on cardiorespiratory variables in anesthetized dogs undergoing mast cell tumor (MCT) excision. DESIGN Randomized, blinded clinical trial. ANIMALS 16 client-owned dogs with MCTs. PROCEDURES In a standardized isoflurane anesthesia session that included mechanical ventilation, dogs received diphenhydramine hydrochloride (1 mg/kg [0.45 mg/lb], IV; n = 8) or an equivalent volume of saline (0.9% NaCl) solution (IV; control treatment; 8) 10 minutes after induction. Cardiorespiratory variables were recorded throughout anesthesia and MCT excision, and blood samples for determination of plasma diphenhydramine and histamine concentrations were collected prior to premedication (baseline), throughout anesthesia, and 2 hours after extubation. RESULTS Cardiorespiratory values in both treatment groups were acceptable for anesthetized dogs. Mean ± SD diastolic arterial blood pressure was significantly lower in the diphenhydramine versus control group during tumor dissection (52 ± 10 mm Hg vs 62 ± 9 mm Hg) and surgical closure (51 ± 10 mm Hg vs 65 ± 9 mm Hg). Mean arterial blood pressure was significantly lower in the diphenhydramine versus control group during surgical closure (65 ± 12 mm Hg vs 78 ± 11 mm Hg), despite a higher cardiac index value. Plasma histamine concentrations were nonsignificantly higher than baseline during maximal manipulation of the tumor and surgical preparation in the diphenhydramine group and during surgical dissection in the control group. CONCLUSIONS AND CLINICAL RELEVANCE IV administration of diphenhydramine prior to MCT excision had no clear clinical cardiorespiratory benefits over placebo in isoflurane-anesthetized dogs.

Effects of oxymorphone hydrochloride or hydromorphone hydrochloride on minimal alveolar concentration of desflurane in sheep

OBJECTIVE

To establish the minimum alveolar concentration (MAC) of desflurane and evaluate the effects of 2 opioids on MAC in sheep.

ANIMALS

8 adult nulliparous mixed-breed sheep.

PROCEDURES

A randomized crossover design was used. Each sheep was evaluated individually on 2 occasions (to allow assessment of the effects of each of 2 opioids), separated by a minimum of 10 days. On each occasion, sheep were anesthetized with desflurane in 100% oxygen, MAC of desflurane was determined, oxymorphone (0.05 mg/kg) or hydromorphone (0.10 mg/kg) was administered IV, and MAC was redetermined. Physiologic variables and arterial blood gas and electrolyte concentrations were measured at baseline (before MAC determination, with end-tidal desflurane concentration maintained at 10%) and each time MAC was determined. Timing of various stages of anesthesia was recorded for both occasions.

RESULTS

Mean ± SEM MAC of desflurane was 8.6 ± 0.2%. Oxymorphone or hydromorphone administration resulted in significantly lower MAC (7.6 ± 0.4% and 7.9 ± 0.2%, respectively). Cardiac output at MAC determination for desflurane alone and for desflurane with opioid administration was higher than that at baseline. No difference was identified among hematologic values at any point. Effects of oxymorphone and hydromorphone on durations of various stages of anesthesia did not differ significantly.

CONCLUSIONS AND CLINICAL RELEVANCE

MAC of desflurane in nulliparous adult sheep was established. Intravenous administration of oxymorphone or hydromorphone led to a decrease in MAC; however, the clinical importance of that decrease was minor relative to the effect in other species.

The Effect of the Canine ABCB1-1Δ Mutation on Sedation after Intravenous Administration of Acepromazine

BACKGROUND

Dog breeds with the ABCB1-1Δ mutation have substantially truncated nonfunctional P-glycoprotein. Dogs homozygous for this mutation (mut/mut) are susceptible to the toxic adverse effects of ivermectin, loperamide, and vincristine. Anecdotal reports suggested ABCB1 mut/mut dogs showed increased depth and duration of acepromazine sedation.

HYPOTHESIS/OBJECTIVES

That ABCB1 mut/mut dogs have increased depth and duration of sedation after acepromazine IV compared to normal dogs (nor/nor).

ANIMALS

Twenty-nine rough-coated collies were divided into 3 groups of dogs based on their ABCB1 genotype: 10 mut/mut, 10 mut/nor, and 9 nor/nor.

METHODS

Dogs were given 0.04 mg/kg of acepromazine IV. Level of sedation, heart rate, respiratory rate, and blood pressure were recorded for 6 hours after acepromazine administration. Area under the curves (AUCs) of the normalized sedation score results were calculated and compared.

RESULTS

The median sedation scores for ABCB1 mut/mut dogs were higher than nor/nor dogs at all time points and were higher in mut/nor dogs for the first 2 hours. These differences were not found to be significant for any individual time point (P > .05). The median sedation score AUC for mut/mut dogs was significantly higher than nor/nor dogs (P = .028), but the AUC for mut/nor dogs was not (P = .45). There were no significant differences between groups for heart rate, respiratory rate, and blood pressure (P > .05).

CONCLUSIONS AND CLINICAL IMPORTANCE

In ABCB1 mut/mut dogs acepromazine dose rates should be reduced and careful monitoring performed during sedation.

Effects of maropitant, acepromazine, and electroacupuncture on vomiting associated with administration of morphine in dogs

OBJECTIVE

To evaluate effects of maropitant, acepromazine, and electroacupuncture on morphine-related signs of nausea and vomiting in dogs and assess sedative effects of the treatments.

DESIGN

Randomized controlled clinical trial.

ANIMALS

222 dogs.

PROCEDURES

Dogs received 1 of 6 treatments: injection of saline (0.9% NaCl) solution, maropitant citrate, or acepromazine maleate or electroacupuncture treatment at 1 acupoint, 5 acupoints, or a sham acupoint. Morphine was administered after 20 minutes of electroacupuncture treatment or 20 minutes after injectable treatment. Vomiting and retching events and signs of nausea and sedation were recorded.

RESULTS

Incidence of vomiting and retching was significantly lower in the maropitant (14/37 [37.8%]) group than in the saline solution (28/37 [75.7%]) and sham-acupoint electroacupuncture (32/37 [86.5%]) groups. The number of vomiting and retching events in the maropitant (21), acepromazine (38), 1-acupoint (35), and 5-acupoint (34) groups was significantly lower than in the saline solution (88) and sham-acupoint electroacupuncture (109) groups. Incidence of signs of nausea was significantly lower in the acepromazine group (3/37 [8.1%]) than in the sham-acupoint group (15/37 [40.5%]). Mean nausea scores for the saline solution, maropitant, and sham-acupoint electroacupuncture groups increased significantly after morphine administration, whereas those for the acepromazine, 1-acupoint electroacupuncture, and 5-acupoint electroacupuncture groups did not. Mean sedation scores after morphine administration were significantly higher in dogs that received acepromazine than in dogs that received saline solution, maropitant, and sham-acupoint electroacupuncture treatment.

CONCLUSIONS AND CLINICAL RELEVANCE

Maropitant treatment was associated with a lower incidence of vomiting and retching, compared with control treatments, and acepromazine and electroacupuncture appeared to prevent an increase in severity of nausea following morphine administration in dogs.

Anaesthetic induction and recovery characteristics of a diazepam-ketamine combination compared with propofol in dogs

Induction of anaesthesia occasionally has been associated with undesirable behaviour in dogs. High quality of induction of anaesthesia with propofol has been well described while in contrast variable induction and recovery quality has been associated with diazepam-ketamine. In this study, anaesthetic induction and recovery characteristics of diazepam-ketamine combination with propofol alone were compared in dogs undergoing elective orchidectomy. Thirty-six healthy adult male dogs were used. After habitus scoring (simple descriptive scale [SDS]), the dogs were sedated with morphine and acepromazine. Forty minutes later a premedication score (SDS) was allocated and general anaesthesia was induced using a combination of diazepam-ketamine (Group D/K) or propofol (Group P) and maintained with isoflurane. Scores for the quality of induction, intubation and degree of myoclonus were allocated (SDS). Orchidectomy was performed after which recovery from anaesthesia was scored (SDS) and times to extubation and standing were recorded. Data were analysed using descriptive statistics and Kappa Reliability and Kendall Tau B tests. Both groups were associated with acceptable quality of induction and recovery from anaesthesia. Group P, however, was associated with a poorer quality of induction (p = 0.014), prolonged induction period (p = 0.0018) and more pronounced myoclonus (p = 0.003), but had better quality of recovery (p = 0.000002) and shorter recovery times (p = 0.035) compared with Group D/K. Diazepam-ketamine and propofol are associated with acceptable induction and recovery from anaesthesia. Propofol had inferior anaesthetic induction characteristics, but superior and quicker recovery from anaesthesia compared with diazepam-ketamine.

Efficacy of orally administered maropitant citrate in preventing vomiting associated with hydromorphone administration in dogs

OBJECTIVE

To evaluate the effectiveness of orally administered maropitant citrate in preventing vomiting after hydromorphone hydrochloride administration in dogs.

DESIGN

Randomized, blinded, prospective clinical study.

ANIMALS

40 dogs with American Society of Anesthesiologists status of I or II, > 6 months of age, and weighing between 24 and 58.2 kg (52.8 and 128.04 lb).

PROCEDURES

Dogs were randomly selected to receive maropitant (2.0 to 4.0 mg/kg [0.9 to 1.8 mg/lb]) or placebo (lactose monohydrate) orally 2 hours prior to receiving hydromorphone (0.1 mg/kg [0.045 mg/lb], IM). A blinded observer recorded the occurrence of vomiting or signs of nausea (eg, salivation or lip-licking) during a 30-minute period after hydromorphone administration. Two-tailed Fisher exact tests were used to compare the incidences of vomiting and signs of nausea with or without vomiting between treatment groups. Results-Of the 20 dogs receiving maropitant, none vomited but 12 (60%) developed signs of nausea. Of the 20 dogs receiving placebo, 5 (25%) vomited and 11 (55%) developed signs of nausea; overall, 16 of 20 (80%) dogs in the placebo treatment group vomited or developed signs of nausea. Compared with the effects of placebo, maropitant significantly decreased the incidence of vomiting but not signs of nausea in dogs administered hydromorphone.

CONCLUSIONS AND CLINICAL RELEVANCE

Among the 40 study dogs, the incidence of vomiting associated with hydromorphone administration was 25%. Oral administration of maropitant prevented vomiting but not signs of nausea associated with hydromorphone administration in dogs.

Cardiovascular effects of orotracheal intubation following anesthetic induction with propofol, ketamine-propofol, or ketamine-diazepam in premedicated dogs

OBJECTIVE

To compare the hemodynamic responses to orotracheal intubation following induction of anesthesia with propofol, ketamine-propofol, and ketamine-diazepam in premedicated dogs.

DESIGN

Prospective, randomized, masked study.

ANIMALS

10 healthy adult Beagles.

PROCEDURES

Dogs were randomly allocated to be anesthetized twice, with a 1-week wash-out interval, by means of 2 of 3 possible protocols (propofol [4 mg/kg {1.8 mg/lb}, n = 6 dogs], ketamine [2 mg/kg {0.9 mg/lb}] and propofol [2 mg/kg; 7], or ketamine [5 mg/kg {2.3 mg/lb}] and diazepam [0.2 mg/kg {0.09 mg/lb}; 6]). After instrumentation, continuous heart rate, systolic arterial blood pressure, mean arterial blood pressure, diastolic arterial blood pressure, cardiac index, stroke volume index, and systemic vascular resistance were recorded. Fifteen minutes after premedication, dogs were anesthetized; all anesthetics were administered IV. After 5 minutes, orotracheal intubation was performed without the use of a laryngoscope. Data were collected prior to intubation (baseline), at intubation, and 30, 60, 90, 120, 150, and 180 seconds thereafter. Results were compared among the 3 groups and over time.

RESULTS

No differences among groups were observed for any variables studied. In all groups, arterial blood pressures were significantly decreased at various time points after intubation. A significant increase in systolic arterial blood pressure was observed between baseline and the 30-second time point in the ketamine-diazepam group. No significant differences were detected over time for the other variables in any group.

CONCLUSIONS AND CLINICAL RELEVANCE

Intubation after anesthetic induction with ketamine-diazepam caused transitory hypertension, whereas intubation after induction with propofol or ketamine-propofol did not cause cardiovascular stimulation. In dogs in which hypertension is a concern, propofol or ketamine-propofol may be a better choice for induction prior to orotracheal intubation.

Comparison of the cardiorespiratory effects of a combination of ketamine and propofol, propofol alone, or a combination of ketamine and diazepam before and after induction of anesthesia in dogs sedated with acepromazine and oxymorphone

OBJECTIVE

To evaluate the cardiorespiratory effects of IV administration of propofol (4 mg/kg), ketamine hydrochloride and propofol (2 mg/kg each; K-P), or ketamine hydrochloride (5 mg/kg) and diazepam (0.2 mg/kg; K-D) before and after induction of anesthesia (IoA) in dogs sedated with acepromazine maleate and oxymorphone hydrochloride.

ANIMALS

10 healthy adult Beagles.

PROCEDURES

Each dog was randomly allocated to receive 2 of 3 treatments (1-week interval). For instrumentation prior to each treatment, each dog was anesthetized with isoflurane. After full recovery, acepromazine (0.02 mg/kg) and oxymorphone (0.05 mg/kg) were administered IV. Fifteen minutes later (before IoA), each dog received treatment IV with propofol, K-P, or K-D. Cardiorespiratory and arterial blood gas variables were assessed before, immediately after, and 5 minutes after IoA.

RESULTS

Compared with findings before IoA, dogs receiving the K-P or K-D treatment had increased cardiac output, oxygen delivery, and heart rate 5 minutes after IoA; K-P administration did not change mean arterial blood pressure or stroke volume and decreased systemic vascular resistance. Propofol decreased mean arterial blood pressure and systemic vascular resistance immediately after IoA but did not change heart rate, cardiac output, or oxygen delivery. All treatments caused some degree of apnea, hypoventilation, and hypoxemia (Pao2 < 80 mm Hg).

CONCLUSIONS AND CLINICAL RELEVANCE

In dogs, K-P treatment maintained mean arterial blood pressure better than propofol alone and increased heart rate, cardiac output, or oxygen delivery, as did the K-D treatment. Supplemental 100% oxygen should be provided during IoA with all 3 treatments.

Effects of maropitant citrate or acepromazine on the incidence of adverse events associated with hydromorphone premedication in dogs

Background

Vomiting is a common complication associated with the use of hydromorphine for pre‐emptive analgesia in dogs. The ideal anti‐emetic protocol for prevention of this complication has not been established.

Hypothesis

Maropitant administered concurrently or before hydromorphone would reduce the incidence of vomiting, signs of nausea, ptyalism, and increased panting compared to administration of acepromazine or a 0.9% saline control.

Animals

Sixty mixed‐breed female dogs scheduled for ovariohysterectomy.

Methods

Randomized, blinded, placebo‐controlled experimental study. Dogs were assigned to 4 experimental groups with 15 dogs per group. All groups received 0.2 mg/kg of hydromorphone IM. Group “Control” received 0.1 mL/kg saline SC 30–45 minutes before hydromorphone, group “Marop1” received 1 mg/kg maropitant SC 30–45 minutes before hydromorphone, group “Ace” received 0.02 mg/kg IM acepromazine 30–45 minutes before hydromorphone, and group “Marop2” received 1 mg/kg SC maropitant concurrently with hydromorphone. A trained and blinded observer documented adverse events from the time hydromorphone was administered until the time dogs were induced for surgery.

Results

Marop1 had significantly less vomiting (0%) compared to Control (87%; P < .01) and Ace (53%; P < .01). Marop2 had significantly less vomiting (27%) compared to Control (P < .01). Marop1 had significantly greater incidence of ptyalism (73%) compared to Ace (P < .01; 20%). Ace showed significantly less panting (33%) compared to Marop2 (93%; P < .01).

Conclusions and Clinical Importance

In healthy dogs, maropitant citrate administered before hydromorphone significantly decreases the incidence of vomiting in dogs but does not improve signs of nausea, ptyalism, or increased panting.

Randomized clinical trial of the effects of a combination of acepromazine with morphine and midazolam on sedation, cardiovascular variables and the propofol dose requirements for induction of anesthesia in dogs

The present study evaluated the effects of acepromazine combined with midazolam and morphine on sedation and cardiovascular variables as well as the propofol dose required for induction of anesthesia in dogs compared with acepromazine-morphine or midazolam-morphine. Dogs were randomly assigned to receive an intramuscular administration of (1) acepromazine (0.05 mg/kg) with 0.5mg/kg of morphine (group AM, n=10), (2) midazolam (0.5mg/kg) with 0.5mg/kg of morphine (group MM, n=9), or (3) acepromazine with midazolam and morphine at the same doses (group AMM, n=10). After 30 min, sedation was assessed by a numeric descriptive scale (NDS, range 0-3) and a simple numerical scale (SNS, range 0-10). Dogs were then administered IV propofol to allow endotracheal intubation. NDS and SNS scores were significantly higher in the AMM than in the MM group (P<0.05). There was a trend towards more dogs presenting with intense sedation (NDS=3) in AMM (6/10 dogs) compared with AM (1/10 dogs) and MM (1/9 dogs) (P=0.057). The propofol dose required for induction of anesthesia was significantly lower in AMM (4.0mg/kg) compared with MM (6.0mg/kg, P<0.01) but not AM (4.6 mg/kg). Heart rate decreased in AM after treatment and after intubation. Blood pressure decreased in groups AM and AMM following treatment and in all groups after intubation. The combination AMM resulted in intense sedation more frequently than AM and MM, and provided the greatest sparing effect in the propofol dose. Administration of AM and AMM but not MM decreased blood pressure although hypotension was not recorded in healthy dogs.

Sedative and analgesic effects of buprenorphine, combined with either acepromazine or dexmedetomidine, for premedication prior to elective surgery in cats and dogs

OBJECTIVE

To evaluate the sedative and analgesic effects of intramuscular buprenorphine with either dexmedetomidine or acepromazine, administered as premedication to cats and dogs undergoing elective surgery.

STUDY DESIGN

Prospective, randomized, blinded clinical study.

ANIMALS

Forty dogs and 48 cats.

METHODS

Animals were assigned to one of four groups, according to anaesthetic premedication and induction agent: buprenorphine 20 μg kg(-1) with either dexmedetomidine (dex) 250 μg m(-2) or acepromazine (acp) 0.03 mg kg(-1), followed by alfaxalone (ALF) or propofol (PRO). Meloxicam was administered preoperatively to all animals and anaesthesia was always maintained using isoflurane. Physiological measures and assessments of pain, sedation and mechanical nociceptive threshold (MNT) were made before and after premedication, intraoperatively, and for up to 24 hours after premedication. Data were analyzed with one-way, two-way and mixed between-within subjects anova, Kruskall-Wallis analyses and Chi squared tests. Results were deemed significant if p ≤ 0.05, except where multiple comparisons were performed (p ≤ 0.005).

RESULTS

Cats premedicated with dex were more sedated than cats premedicated with acp (p < 0.001) and ALF doses were lower in dex cats (1.2 ± 1.0 mg kg(-1) ) than acp cats (2.5 ± 1.9 mg kg(-1)) (p = 0.041). There were no differences in sedation in dogs however PRO doses were lower in dex dogs (1.5 ± 0.8 mg kg(-1) ) compared to acp dogs (3.3 ± 1.1 mg kg(-1) ) (p < 0.001). There were no differences between groups with respect to pain scores or MNT for cats or dogs.

CONCLUSION

Choice of dex or acp, when given with buprenorphine, caused minor, clinically detectable, differences in various characteristics of anaesthesia, but not in the level of analgesia.

CLINICAL RELEVANCE

A combination of buprenorphine with either acp or dex, followed by either PRO or ALF, and then isoflurane, accompanied by an NSAID, was suitable for anaesthesia in dogs and cats undergoing elective surgery. Choice of sedative agent may influence dose of anaesthetic induction agent.

Comparison of tissue oxygen saturation in ovariohysterectomized dogs recovering on room air versus nasal oxygen insufflation

OBJECTIVE

To compare tissue oxygen saturation in ovariohysterectomized dogs recovering postoperatively on room air versus nasal oxygen insufflation.

DESIGN

Prospective clinical study.

SETTING

University teaching hospital.

ANIMALS

Twenty dogs undergoing ovariohysterectomy.

INTERVENTIONS

Dogs were randomized to breathe either room air or 100 mL/kg/min of nasal oxygen insufflation for 2 hours postoperatively. Tissue oxygen saturation (StO(2)) was evaluated at 2 mm and 20 mm lateral to the surgical incision, as well as in the inguinal region using a noninvasive tissue oximeter.

MEASUREMENTS AND MAIN RESULTS

In dogs recovered on nasal oxygen insufflation (n = 10), tissue oxygen saturation was significantly higher--20 mm from the surgical site (88.44 ± 2.50%, P = 0.02) and in the inguinal region (83.56 ± 1.91%, P = 0.032)-- compared to dogs recovered on room air (n = 10, 79.11% ± 2.50 and 77.12% ± 1.91, respectively).

CONCLUSIONS

In ovariohysterectomized dogs, oxygen supplementation for 2 hours postoperatively improves tissue oxygen saturation 20 mm adjacent to the linea alba and in the inguinal region. Oxygen supplementation in postoperative dogs is an inexpensive and easily applicable method to improve tissue oxygen saturation.

Effects of sedation with acepromazine maleate and buprenorphine hydrochloride on femoral artery blood flow in healthy dogs

The purpose of this study was to qualify and quantify the femoral artery blood flow by duplex Doppler ultrasonography (DDU) in healthy dogs, before and after the administration of a combination of acepromazine maleate and buprenorphine hydrochloride (ACP-BPN). Seven healthy adult mongrel dogs and three adult beagles were used. Heart rate, arterial blood pressure and measurement of femoral artery blood flow by DDU were also recorded. The DDU measurements were: femoral artery diameter (FAD), peak systolic velocity (PSV), early retrograde (EDV) and end diastolic velocities (EnDV), mean velocity (BMV), pulsatility index (PI), flow velocity integral (FVI) and femoral blood flow (FBF). After 30 min, combination ACP-BPN was administered intramuscularly, and all the measurements were recorded again. The ACP-BPN protocol induced a significant decrease in systolic, mean, and diastolic arterial blood pressure, and heart rate. A significant increase in peak systolic velocity and integral flow velocity integral of the femoral blood were obtained. The Doppler spectra of the blood flow in the femoral artery revealed a spectral dispersion pattern after ACP-BPN administration in all the dogs. These results demonstrate that despite quantitative and qualitative changes, the overall femoral blood flow (FBF) is not significantly modified.

Experimental Pharmacodynamics and Analgesic Efficacy of Liposome-Encapsulated Hydromorphone in Dogs

The purpose of this study was to determine the experimental side effects of liposome-encapsulated hydromorphone (LE-Hydro) in beagles and to evaluate LE-Hydro analgesia in dogs undergoing ovariohysterectomies (OVH). Beagles were injected subcutaneously with 1–3 mg/kg LE-Hydro or 0.1 mg/kg hydromorphone. Dogs were evaluated for sedation, temperature, respiratory rate, and heart rate. OVH dogs were injected with 2 mg/kg LE-Hydro subcutaneously or 0.2 mg/kg morphine and 0.05 mg/kg acepromazine intramuscularly. Side effects of LE-Hydro were within clinically acceptable limits. The analgesic efficacy was superior in dogs administered LE-Hydro at 12 hr postsurgically. LE-Hydro provided adequate, durable analgesia in dogs undergoing OVH.

A comparison of the effects of hydromorphone HCl and a novel extended release hydromorphone on arterial blood gas values in conscious healthy dogs

The purpose of this study was to evaluate arterial blood gases in dogs that were given hydromorphone or extended release liposome-encapsulated hydromorphone (LEH). Dogs were randomly administered LEH, n=6, (2.0 mg kg(-1)), hydromorphone, n=6, (0.2 mg kg(-1)) or a placebo of blank liposomes, n=3, subcutaneously on separate occasions. Arterial blood samples were drawn at serial time points over a 6-h time period for blood gas analysis. There was no change from baseline values in P(a)CO(2), P(a)O(2), (HCO(3)-), pH, and SBEc in the dogs that received the placebo. Administration of hydromorphone resulted in significant increases in P(a)CO(2) (maximum (mean+SD] 44.4+1.1mm of Hg) and significant decreases in P(a)O(2) (minimum (mean+SD) 82.4+4.7 mm of Hg) and pH (minimum (mean+SD) 7.31+0.01) compared with baseline. Administration of LEH resulted in significant increases in P(a)CO(2) (maximum (mean+SD) 44.6+0.9 mm of Hg) and significant decreases in P(a)O(2) (minimum (mean+SD) 84.8+2.6mm of Hg) and pH (minimum (mean+SD) 7.34+0.02) compared with baseline. There was no significant difference between these two groups at any time point. The changes observed in P(a)CO(2), P(a)O(2), and pH, however, were within clinically acceptable limits for healthy dogs. LEH was determined to cause moderate changes in arterial blood gas values similar to those caused by hydromorphone.

Antinociceptive and side-effects of hydromorphone after subcutaneous administration in cats

The subcutaneous (SC) route is often chosen for drug administration in cats because it is easier to perform than intravenous (IV) injection and is perceived as less painful than intramuscular (IM) injection. However, little is known of how the route of administration influences the pharmacodynamics of drugs. This study measured the changes in skin temperature and thermal threshold (TT) and recorded the side-effects after SC injection of 0.1mg/kg of hydromorphone in six cats. Time to peak TT was 105min. Skin temperature was elevated at 15min and between 45 and 360min. Five cats vomited and two exhibited marked dysphoria. Compared to previously published studies of IV and IM administration of hydromorphone, the SC route results in a slower onset of peak effect, a shorter duration of antinociception and is associated with more undesirable side-effects. As with IV and IM injections, SC administration of hydromorphone at 0.1mg/kg is associated with a significant elevation in skin temperature. Overall, the SC route appears to have the least utility.