The history and pharmacology of fentanyl: relevance to a novel, long-acting transdermal fentanyl solution newly approved for use in dogs

Pharmacokinetics and Physiological Effects of a Single Oral Dose of Oxycodone in Healthy Dogs: A Pilot Study

Oxycodone, a full mu opioid receptor agonist prescribed for moderate-to-severe pain in people, could provide outpatient analgesia for dogs with post-operative or cancer pain. To determine the pharmacokinetic profile and physiological side effects of a single oral (PO) dose, five healthy, 2-year-old, castrated male hounds were administered a standard amount of food, with or without immediate-release oxycodone (1 mg/kg), in random order, separated by 1 month. At intervals between 0.25 and 8 h later, blood was sampled to measure plasma oxycodone concentration using ultra high-pressure liquid chromatography with mass spectrometry detection, and vital signs were evaluated. Pharmacokinetic variables were estimated using noncompartmental analysis. Maximum plasma concentration (Cmax) was 58.6 (39.3, 61.6) ng/mL, time to maximal plasma concentration (tmax) was 1.5 (0.5, 2.0) h, elimination half-life (t1/2el) was 2.6 (2.0, 6.7) h, area under the curve from time 0 to last measurement (AUC0-t) was 236.1 (204.6, 256.0) ng-h/mL, and mean residence time (MRT) was 3.9 (3.4, 9.8) h. Computer simulations using the calculated pharmacokinetic data predicted that 1 mg/kg PO every 6 h would achieve peak (Cmax) and trough (minimum plasma concentration, Cmin) of 69.4 (60.8, 74.6) and 17.0 (15.5, 46.7), respectively, at steady state. Assuming minimum effective analgesic concentration is similar in humans and dogs (~25 mg/mL), therapeutic concentrations were achieved, but administration more frequently than every 6 h would be necessary. Oxycodone produced a significantly lower rectal temperature 1 and 4 h after administration.

Balancing acts: The dual faces of fentanyl in medicine and public health

Fentanyl is a potent synthetic opioid widely used in medicine for its effective analgesic properties, particularly in surgical procedures and in the treatment of severe, chronic pain. In recent decades, however, there has been a worrying increase in the illicit use of fentanyl, particularly in North America. This rise in illicit use is concerning because fentanyl is associated with polydrug abuse, which adds layers of complexity and dangerous. This review provides a comprehensive examination of fentanyl, focusing on its synthesis and medical use. It also discusses the significance of the piperidine ring in medicinal chemistry as well as the critical role of fentanyl in pain management and anesthesia. Furthermore, it addresses the challenges associated with the abuse potential of fentanyl and the resulting public health concerns. The study aims to strike a balance between the clinical benefits and risks of fentanyl by advocating for innovative uses while addressing public health issues. It examines the chemistry, pharmacokinetics and pharmacodynamics of fentanyl and highlights the importance of personalized medicine in the administration of opioids. The review underscores the necessity of continuous research and adaptation in both clinical use and public health strategies.

Identification and biophysical characterization of a novel domain-swapped camelid antibody specific for fentanyl

Opioid use disorders (OUD) and overdoses are ever-evolving public health threats that continue to grow in incidence and prevalence in the United States and abroad. Current treatments consist of opioid receptor agonists and antagonists, which are safe and effective but still suffer from some limitations. Murine and humanized monoclonal antibodies (mAb) have emerged as an alternative and complementary strategy to reverse and prevent opioid-induced respiratory depression. To explore antibody applications beyond traditional heavy-light chain mAbs, we identified and biophysically characterized a novel single-domain antibody specific for fentanyl from a camelid variable-heavy-heavy (VHH) domain phage display library. Structural data suggested that VHH binding to fentanyl was facilitated by a unique domain-swapped dimerization mechanism, which accompanied a rearrangement of complementarity-determining region loops leading to the formation of a fentanyl-binding pocket. Structure-guided mutagenesis further identified an amino acid substitution that improved the affinity and relaxed the requirement for dimerization of the VHH in fentanyl binding. Our studies demonstrate VHH engagement of an opioid and inform on how to further engineer a VHH for enhanced stability and efficacy, laying the groundwork for exploring the in vivo applications of VHH-based biologics against OUD and overdose.

Pharmacokinetics and pharmacodynamics of intranasal and intramuscular administration of naloxone in working dogs administered fentanyl

BACKGROUND

Working dogs exposed to narcotics might require reversal in the field.

OBJECTIVE

To explore the pharmacokinetic and pharmacodynamic effects of naloxone administered intramuscularly (IM) or intranasally (IN) to reverse fentanyl sedation in working dogs.

ANIMALS

Ten healthy, working dogs aged 1.7 ± 1 year and weighing 26 ± 3 kg.

METHODS

In this randomized, controlled cross-over study dogs received either 4 mg of naloxone IN or IM 10 minutes after fentanyl (0.3 mg IV) administration. Sedation was assessed at baseline and 5 minutes after fentanyl administration, then at 5, 10, 15, 20, 25, 30, 60 and 120 minutes after reversal with naloxone. Blood samples for naloxone detection were obtained at 0, 5, 10, 30, 60 and 120 minutes. Pharmacokinetic parameters and sedation scores were compared between IM and IN naloxone groups.

RESULTS

There was a significant increase in sedation score from baseline (0.25 [-4 to 1] IM; 0 [-2 to 1] IN) after fentanyl administration (11 [5-12] IM; 9.25 [4-11] IN), followed by a significant reduction at 5 (0.5 [-0.5 to 1.5] IM; 1.25 [-1.5 to 4.5] IN) through 120 minutes (-0.5 [-2 to 1] IM; 0 [-4.5 to 1] IN) after reversal with naloxone. Route of administration had no significant effect on sedation score. Maximum plasma concentration was significantly lower after IN administration (11.7 [2.8-18.8] ng/mL IN, 36.7 [22.1-56.4] ng/mL IM, P < .001) but time to reach maximum plasma concentration was not significantly different from IM administration.

CONCLUSION AND CLINICAL IMPORTANCE

Although IM administration resulted in higher naloxone plasma concentrations compared to IN, reversal of sedation was achieved via both routes after administration of therapeutic doses of fentanyl.

Pharmacokinetic Evaluation of a Novel Transdermal Ketoprofen Formulation in Healthy Dogs

Dogs undergo various surgical procedures such as castration, ovariohysterectomy, and other orthopedic procedures, which are known to cause inflammation and pain. Non-steroidal anti-inflammatory drugs (NSAIDs) are very effective analgesics for alleviating postoperative pain in veterinary medicine. Ketoprofen is currently approved in Australia and the United States for treating different painful conditions in dogs. This study evaluated the pharmacokinetic parameters of ketoprofen after intravenous (IV) and transdermal (TD) administration in healthy dogs. A novel transdermal ketoprofen (TDK) formulation containing 20% ketoprofen, dissolved in a combination of 45:45% isopropanol and Transcutol, along with 10% eucalyptus oil, was developed and evaluated for in vitro dermal permeation using Franz diffusion cells. A crossover study was then conducted to determine the pharmacokinetic parameters of the formulation in six dogs following IV ketoprofen (1 mg/kg) and TDK (10 mg/kg) administration. A liquid chromatography–mass spectrometry (LC-M/MS) method was used to measure plasma concentrations of ketoprofen over time, and a non-compartmental analysis determined the pharmacokinetic parameters. The mean terminal elimination half-life (T_½ h), AUC_0-t (µg·h/mL), and mean residence time (MRT, h) between IV and TDK groups were 4.69 ± 1.33 and 25.77 ± 22.15 h, 15.75 ± 7.72 and 8.13 ± 4.28 µg·h/mL, and 4.86 ± 1.81 and 41.63 ± 32.33 h, respectively. The calculated bioavailability (F%) was ~7%, with a lag time of 30 min to achieve effective plasma concentrations after the application of TDK.

Aspects in controlled drug delivery for topical applications in veterinary medicine

The controlled release of drugs is an appealing area of research as it provides numerous benefits in veterinary and human medicine. In this paper we attempt to analyze certain aspects related to topical drug delivery systems, their successes and failures, and their place in veterinary medicine. Some emphasis is given to the pharmaceutical aspects of the delivery systems, where the material available made it possible. Purely topical devices, such as cattle ear tags and various collars, as well as some topically administered bioavailable delivery systems are discussed. Special attention is given to hitherto under-evaluated delivery systems, such as topical varnishes. A carefully selected bibliography aims to lead the reader easily to the facts, without providing overwhelming data of varying quality. We believe that the paper may be of interest to practicing veterinarians as well as to pharmaceutical scientists working or considering practice in the area.

Fentanyl patch versus tramadol for the control of postoperative pain in canine ovariectomy and mastectomy

OBJECTIVES

The purpose of the present study was to evaluate the postoperative analgesic efficacy of fentanyl patches versus subcutaneous tramadol after canine ovariectomy, with and without unilateral mastectomy.

MATERIALS AND METHODS

A total of 40 female dogs were included in the present study, all of which were domesticated, healthy and 4-12 years of age. The animals were divided into four groups (n = 10 per group) based on the surgery and the analgesic protocol used: the TO group only underwent ovariectomy, and received postoperative tramadol; the TM group underwent both ovariectomy and mastectomy, and received postoperative tramadol; the FO group only underwent ovariectomy, and received fentanyl patches; and the FM group underwent both ovariectomy and mastectomy, and received fentanyl patches. Postoperative pain was evaluated every 4 h for 24 h using a numeric analogue scale (NAS) and a modified Glasgow Composite Measure Pain Scale Short Form (CMPS-SF).

RESULTS

The results of the present study showed that patients in all four groups tolerated postoperative surgical stress well. Analysis of variance for repeated measures did not show significant differences in the NAS scores and in Glasgow CMPS-SF between groups in terms of pain scores or rescue analgesia.

CLINICAL SIGNIFICANCE

These results indicated that the analgesic effect of the fentanyl patch was similar to that of subcutaneous (SC) tramadol in female dogs after ovariectomy, with and without unilateral mastectomy, suggesting that the fentanyl patch may represent a valid supplementary tool for the control of postoperative pain in animals after surgery.

Long-Term Analgesia following a Single Application of Fentanyl Transdermal Solution in Pigs

INTRODUCTION

In animal research, obtaining efficient and constant pain control is regulatory but challenging. The gold standard pain management consists of opioid analgesic administration, such as buprenorphine or fentanyl extended-release patches. However, as in all drugs with a short half-life time, repeated buprenorphine administrations are needed, leading to multiple injections that affect the research protocol. On the other hand, fentanyl patch efficacy is discussed in some species. These elements highlight the need of an optimal formulation of analgesic drugs for laboratory animals. In this study, we investigated how Recuvyra®, a fentanyl transdermal solution (FTS), validated in dog perioperative pain management, could provide sustained analgesia after a single topical administration in pigs in a surgical context.

METHODS

A total of 11 minipigs were used in this study. As a preliminary experiment, two different doses were tested as a single application on five pigs: two pigs at full dose (2.6 mg/kg) and three pigs at half dose (1.3 mg/kg). Plasma fentanyl dosages were performed during 4 consecutive days, using liquid chromatography with tandem mass spectrometry detection. The efficacy of FTS was then evaluated in a perioperative period. Six minipigs benefited from a surgical intervention comprising a laparotomy. The FTS was blotted on the skin in a single application 20 min before the surgical incision and plasma fentanyl dosages, clinical examination (body weight, food intake, heart rate, and body temperature) and pain assessment were performed for 7 consecutive days.

RESULTS

During the preliminary experiment, all fentanyl concentrations reached the minimum effective concentration (MEC) extrapolated in pigs (fentanylemia ≥0.2 ng/mL) throughout the 4 days. The half dose was chosen for the next step of the study. After the surgical intervention, all plasma fentanyl concentrations remained above the MEC up to 7 days post administration. Pig clinical examinations and pain evaluations showed efficient and constant pain control at the half dose, and few adverse events were observed.

DISCUSSION AND CONCLUSION

This study confirms the pharmacological and clinical efficacy of FTS at 1.3 mg/kg in pigs throughout at least 7 postoperative days following laparotomy. The clinical analgesic effect of FTS appears more efficient and well-tolerated than the one observed with repeated injections of buprenorphine. This analgesic drug formulation could be universally used in animal research to provide optimal perioperative pain management and long-term analgesia.

Evaluation of the analgesic effect of fentanyl-ketamine and fentanyl-lidocaine constant rate infusions in isoflurane-anesthetized dogs undergoing thoracolumbar hemilaminectomy

OBJECTIVE

To evaluate anesthetic conditions and postoperative analgesia with the use of intraoperative constant rate infusions (CRIs) of fentanyl-lidocaine or fentanyl-ketamine in dogs undergoing thoracolumbar hemilaminectomy.

STUDY DESIGN

Prospective, randomized, blinded, clinical study.

ANIMALS

A total of 32 client-owned dogs.

METHODS

Dogs were premedicated with fentanyl (5 μg kg^-1) administered intravenously (IV), anesthesia was induced with IV alfaxalone and maintained with isoflurane. Fentanyl (0.083 μg kg^-1 minute^-1) was infused IV with either ketamine (0.5 mg kg^-1; then 40 μg kg^-1 minute^-1; group KF) or lidocaine (2 mg kg^-1; then 200 μg kg^-1 minute^-1; group LF) assigned randomly. Heart rate, noninvasive arterial pressures, respiratory rate, esophageal temperature, end-tidal partial pressure of carbon dioxide and isoflurane concentration were recorded throughout anesthesia. Maintenance of anesthesia, recovery and postoperative pain (Glasgow Composite Pain Scale) were scored. Cardiopulmonary data were analyzed using a two-way anova with repeated measures, demographics of the two groups with a t test, and scores with Mann-Whitney U test, with p < 0.05.

RESULTS

All dogs recovered from anesthesia without complications. No significant difference was found between groups for cardiopulmonary variables, total anesthesia time, sedation score and requirement for postoperative sedation or for rescue analgesia. Anesthetic maintenance score was of lower quality in KF than in LF [median (interquartile range): 0 (0-0.5) versus 0 (0-0); p = 0.032)], but still considered ideal. Recovery score was higher and indicative of less sedation in LF than in KF [1 (1-1.5) versus 0.5 (0-1); p < 0.0001]. Pain score was higher in KF than in LF [2 (1-3) versus 1 (1-2); p = 0.0009].

CONCLUSIONS AND CLINICAL RELEVANCE

Both CRIs of KF and LF provided adequate anesthetic conditions in dogs undergoing thoracolumbar hemilaminectomy. Based on requirement for rescue analgesia, postoperative analgesia was adequate in both groups.

Development of a Training Program for Law Enforcement K9 Handlers to Administer Naloxone

As the opioid epidemic continues across the United States, law enforcement K9s (LEK9s) are at increased risk of accidental exposure and overdose. This study evaluated a novel training program teaching handlers to administer naloxone to their LEK9 in the event of an overdose. Seventy-five LEK9 handlers from a governmental agency attended a naloxone training session. A presurvey given to the handlers evaluated their knowledge of opioid overdose in LEK9s and their confidence administering naloxone. Officers were educated via a PowerPoint presentation about naloxone and how to administer it to their LEK9. A postsurvey evaluated changes in their knowledge and confidence as a result of the presentation. Sixty-two presurveys and 47 postsurveys were completed. Nearly all handlers had never given their LEK9 an intramuscular or intranasal injection. Most handlers were not comfortable monitoring their LEK9's vital signs for an opioid overdose. After the training, handlers demonstrated a mild increase in comfort level administering intramuscular and intranasal naloxone (15 and 14% increase, respectively). Comfort level monitoring vital signs and symptoms of an opioid overdose increased 38 and 32%, respectively. Handlers may not be fully prepared to assess and treat their LEK9 and may benefit from a targeted training program teaching them to administer naloxone.

The US Opioid Epidemic and Its Impact on US General Practice Veterinarians

Objective: To assess the impact of the human opioid epidemic and associated shortages in drug supply on US general practice veterinarians. Design: Cross-sectional study. Sample: Members of the Veterinary Information Network (VIN). Procedures: An electronic survey was used to examine veterinarians' views regarding opioid use in veterinary medicine and the impact of the opioid shortage on the provision of care. The survey was distributed via the VIN data collection portal from October 12-November 6, 2018. Results: 697 veterinarians completed the survey. Most (99.7%) reported using, dispensing or prescribing opioids in veterinary practice. The most commonly used opioids were buprenorphine, tramadol and butorphanol. While most veterinarians (83.3%) reported difficulty in ordering opioids over the last 6 months, this decreased to 59.0% in the last month. The most difficult drugs to obtain were hydromorphone, morphine, injectable fentanyl, and oxymorphone. The reported rate of difficulty in obtaining all these drugs lessened over time. However, the opioid shortage caused significant difficulty in providing appropriate pain management for 41.1% of participants, and affected the ability of 44.8% of respondents to provide optimal anesthesia. Conclusions and Clinical Relevance: Veterinarians' ability to provide opioids for their patients has been impacted by the opioid shortage, with a greater impact on full mu opioid agonists as compared to drugs like butorphanol, buprenorphine, and tramadol. The results confirm the important role of opioid analgesics in the delivery of modern veterinary medicine and highlight the importance of medical health professionals being able to access these critical medications.

The Carle-Illinois (Urbana, Illinois USA) Treatment Protocol for Law Enforcement K9s: Guidelines for Emergency Medical Services

This document is a resource for Emergency Medical Services (EMS) treating an injured law enforcement K9 (LEK9) in the field and/or during transport by ambulance to a veterinary hospital. A Joint Task Force on Working Dog Care was created, which included veterinarians, EMS directors, EMS physicians, and canine handlers, who met to develop a treatment protocol for injured LEK9s. The protocol covers many major life-threatening injuries that LEK9s may sustain in the line of duty, and also discusses personnel safety and necessary equipment. This protocol may help train EMS providers to save the life of an injured LEK9.

Trends in the medical supply of fentanyl and fentanyl analogues: United States, 2006 to 2017

Fentanyl is an important opioid for pain management, but also has exceptional potential for misuse. Seven states have implemented opioid prescribing laws. The objectives of this study were to: 1) characterize the temporal pattern of fentanyl, fentanyl analogue, and other opioid use over the past decade, and 2) determine whether opioid prescribing laws impacted fentanyl use in the US. Drug weights were obtained from the US Automated Reports of Consolidated Orders System (June 2018), a comprehensive publically available resource, from 2006 to 2017 for fentanyl, sufentanil, remifentanil, alfentanil, other prescription opioids, and analyzed by presence of a state opioid prescribing law. Fentanyl, corrected for population, was reduced from 2016 to 2017 (-17.9%) and these decreases significantly exceeded the changes in hydrocodone (-12.3%), oxycodone (-10.1%), morphine (-13.3%), or codeine (-8.8%). Fentanyl showed a particularly large decline in Maine, a state with a strong opioid prescribing law. There was a 3.5 fold difference in fentanyl (μg per capita) in Alaska (488.2) relative to Oregon (1718.4). Hospital use of remifentanil and sufentanil tripled from 2006 to 2017. Although all states experienced a 2016 to 2017 decline in fentanyl, and this reduction was larger than many other prescription opioids, the rate of decline varied over three-fold between states. Strong state laws may account for a portion of the variance in fentanyl and other opioid reductions. The population health risks of fentanyl and fentanyl analogues warrants ongoing vigilance.

Evaluation of the analgesic and pharmacokinetic properties of transdermally administered fentanyl in goats

OBJECTIVE

Evaluate the analgesic properties and pharmacokinetics of transdermal fentanyl patches (TFPs) in goats.

DESIGN

Prospective, randomized study.

SETTING

Preclinical Testing Facility at a University Teaching Hospital.

ANIMALS

Thirty-four adult female Boer-cross goats.

INTERVENTIONS

Goats underwent surgery as part of a concurrent orthopedic research study. Twelve hours prior to surgery, each goat received a TFP (target dosage of 2.5 μg/kg/h), or a placebo patch with analgesia provided by buprenorphine (0.01 mg/kg, IM, q 6 h). Patches were removed after 72 hours. Blood was sampled at specified intervals, up to 84 hours following TFP placement. Plasma concentrations of fentanyl (FEN) were determined using liquid chromatography-mass spectrometry. Postoperative pain assessments were performed by two independent blinded observers.

MEASUREMENTS AND MAIN RESULTS

TFPs were applied at a mean (± standard deviation, SD) dose of 2.54 ± 0.36 μg/kg/h. No adverse events occurred. Pain scores between TFP and BUP groups were not significantly different at any time point. Mean plasma FEN concentration (± SD) 2 hours following patch application was 1.06 ± 0.85 ng/mL, and remained above 0.5 ng/mL for 40 hours. Maximum mean plasma FEN concentration (C_max ) was 1.84 (ranging from 0.81 to 3.35) ng/mL with average time to maximum concentration (T_max ) of 12 hours after patch application.

CONCLUSIONS

TFP resulted in consistent FEN absorption and plasma concentrations within the human and ovine therapeutic ranges. Pain scores for goats administered TFP were not different than those administered buprenorphine. Ease of administration, duration of analgesia, and decreased dosing frequency make TFPs an attractive option for pain management in goats.

Biochemical, Oxidative, and Physiological Changes Caused by Acute Exposure of Fentanyl and Its 3 Analogs in Rodents

Synthesis and bioefficacy of fentanyl and its 8 new 1-substituted analogs (1-8) were earlier reported by us. Of these 8 compounds, N-(1-(2-phenoxyethyl)-4-piperidinyl)propionanilide (2), N-isopropyl-3-(4-( N-phenylpropionamido)piperidin-1-yl)propanamide (5), and N- t-butyl-3-(4-( N-phenylpropionamido)piperidin-1-yl) propanamide (6) were found to be more effective and less toxic compared to fentanyl. The present study reports the acute effect of fentanyl (0.50 Median Lethal Dose (LD₅₀); intraperitoneal) and its 3 analogs (2, 5, and 6) on various biochemical and oxidative parameters in mice and various physiological parameters in rats. Blood alkaline phosphatase (1 hour and 7 days) and urea levels (1 hour) were significantly elevated by fentanyl, while alanine aminotransferase levels (1 hour) were increased by both fentanyl and analog 2 compared to the corresponding control. Increase in partial pressure of carbon dioxide and decrease in partial pressure of oxygen were also caused by fentanyl and analog 2 (1 hour). Analog 6 alone elevated malondialdehyde levels in the brain, liver, and kidney tissues (7 days). The LD₅₀ of fentanyl and analogs 2, 5, and 6 were found to be 0.879, 87.88, 69.80, and 55.44 mg/kg, respectively, in rats. Significant decrease in heart rate, mean arterial pressure, respiratory rate (RR), and neuromuscular transmission was produced by fentanyl and analog 2, while analog 5 decreased the RR alone. The changes, particularly the respiratory depression, were found to be reversed by naloxone, a μ-receptor antagonist. Thereby, indicating involvement of μ-receptor mediated effects of the compounds. To conclude, all the analogs were found to be less toxic compared to fentanyl, suggesting their possible role in pain management.

The Pharmacology of Spinal Opioids and Ziconotide for the Treatment of Non-Cancer Pain

Background

Intrathecal drug delivery has undergone a revitalization following a better understanding of this delivery route and its pharmacokinetics. Driven by patient safety and outcomes, clinicians are motivated to rethink the traditional spinal infusion pump patient selection criteria and indications. We review the current understanding of the pharmacology of commonly employed intrathecal agents and the clinical relevance.

Methods

Search strategies for data acquisition included Medline database, PubMed, Google scholar, along with international and national professional meeting content, with key words including pharmacology of opioids, intrathecal therapy, ziconotide, pharmacokinetics, and intrathecal drug delivery. The search results were limited to the English language.

Results

Over 300 papers were identified. The literature was condensed and digested to evaluate the most commonly used medications in practice, sto serve as a foundation for review. We review on-label medications: ziconotide and morphine, and off label medications including fentanyl, sufentail, and hydromorphine.

Conclusion

Intrathecal therapy has level-one evidence for use for malignant pain and nonmalignant pain, with continued cost savings and improved safety. To most effectively serve our patients, a clear appreciation for the pharmacology of these commonly employed medication is paramount..

Propofol-fentanyl interaction in Beagles - Apnea, response to mechanical ventilation, endotracheal tube, and tetanic stimulation

The objective of this study was to characterize the propofol-fentanyl interaction in Beagles for four pharmacodynamic endpoints: apnea, response to mechanical ventilation, endotracheal tube, and tetanic stimulation. After anesthesia was induced with varying combinations of propofol and fentanyl, the pharmacodynamic endpoints were assessed in intubated dogs (n=6) using the cross-over design. Effective concentrations of propofol plasma concentration (Cp) and fentanyl Cp were assessed using additive, reduced Greco, Minto, and hierarchical interaction models. The interaction was best described as synergistic by the hierarchical model. A 1ng/mL fentanyl Cp reduced the effective propofol Cp to half or less of that without fentanyl for all endpoints. An additional increment of fentanyl Cp to 5ng/mL or higher hardly reduced effective propofol Cp for all endpoints except response to tetanic stimulation. Additionally, the effective propofol Cp in 50% dogs for response to tetanic stimulation (15% increase of heart rate) was lower than that for the other endpoints at fentanyl Cp >7ng/mL. Peripheral oxygen saturation decreased below 90% after extubation in five treatments in which fentanyl Cps were ≥5ng/mL. Propofol and fentanyl interacted synergistically. To avoid patient-ventilator dyssynchrony and hypoxemia after extubation, fentanyl Cp at 1-5ng/mL may be appropriate in intubated dogs. When a dog responds to mechanical ventilation or endotracheal tube at a high fentanyl Cp >5ng/mL under propofol anesthesia even if the dog tolerate to tetanic stimulation, it may be necessary to increase propofol Cp to eliminate the responses because an additional fentanyl may be little impact.

Respiratory Support for Pharmacologically Induced Hypoxia in Neonatal Calves

Practical methods to provide respiratory support to bovine neonates in a field setting are poorly characterised. This study evaluated the response of healthy neonatal calves with pharmacologically induced respiratory suppression to nasal oxygen insufflation and to continuous positive airway pressure (CPAP) delivered via an off-the-shelf device. Ten calves were randomised to receive either nasal oxygen insufflation (Group 1, n = 5) or CPAP (Group 2, n = 5) as a first treatment after induction of respiratory depression by intravenous administration of xylazine, fentanyl, and diazepam. Calves received the alternate treatment after 10 minutes of breathing ambient air. Arterial blood gas samples were obtained prior to sedation, following sedation, following the first and second treatment, and after breathing ambient air before and after the second treatment. Oxygen insufflation significantly increased arterial oxygen partial pressure (PaO₂) but was also associated with significant hypercapnia. When used as the first treatment, CPAP was associated with significantly decreased arterial partial pressure of carbon dioxide but did not increase PaO₂. These results suggest that the use of CPAP may represent a practical method for correction of hypercapnia associated with inadequate ventilation in a field setting, and further research is required to characterise the use of CPAP with increased inspired oxygen concentrations.

Transdermal fentanyl and its use in ovine surgery

Fentanyl delivered via a transdermal patch has the potential to decrease the need for post-operative handling of sheep undergoing surgical procedures. Two studies were performed to test: (1) the ideal timing for the application of pre-emptive analgesic patches and (2) the efficacy of a 2 µg/kg/h dose, as extrapolated from other species. The first study had sheep divided into two groups. Group 1 had a fentanyl patch applied for 24 h prior to a patch change and group 2 had a fentanyl patch applied 72 h prior to a change. The second study applied the results obtained in the first and tested the efficacy of 2 µg/kg/h as an effective dose in an orthopaedic surgical environment. Results indicated that the ideal time for pre-emptive fentanyl patch administration is 24-36 h prior to surgery and that 2 µg/kg/h is an effective minimum therapeutic dose rate for the use of fentanyl as an analgesic in an orthopaedic surgical environment.

Sedation and analgesia with fentanyl and etomidate for intrathecal injection in childhood leukemia patients

In this study, we tried to find a safe as well as fast effective treatment for sedation and analgesia for intrathecal injection in childhood leukemia patients, relieving treatment difficulties and pain, increasing the success rate of single intrathecal injection.The patients were divided into the experimental group (fentanyl combined with etomidate) and the control group (lidocaine only) randomly. The experimental group was given fentanyl 1 to 2 μg/kg intravenously first, then etomidate 0.1 to 0.3 mg/kg intravenously after the pipe washed. The patients younger than 1.5 years or who did not achieve satisfied sedative and analgesic situation received an additional time of etomidate (0.1-0.3 mg/kg). The patients were given oxygen at the rate of 4-5 L/min during the whole operation, and the finger pulse oximeter was used simultaneously to detect the changes in heart rate (HR) and blood oxygen saturation (SpO2). The doctors who performed the procedures assessed the quality of sedation and analgesia.In the experimental group, the patients' HR increased slightly after given fentanyl combined with etomidate. The patients' SpO2 was stable. Most patients achieved a good sedative and analgesic state within 1 to 2 minutes, and no case of respiration depression or cardiac arrhythmias occurred during the whole operation. The wake-up time was 55.42 ± 20.62 min. In the control group, the patients were not very cooperative during the intrathecal injection, which made the procedures very difficult.During intrathecal injection, pain obviously reduced and the success rate of single lumbar puncture increased. It is safe and effective to apply fentanyl combined with etomidate for sedation and analgesia.

Perioperative evaluation of tumescent anaesthesia technique in bitches submitted to unilateral mastectomy

BACKGROUND

Tumescent anaesthesia (TA) is a widely used technique in oncologic surgeries necessitating large resection margins. This technique produces transoperative and postoperative analgesia, reduces surgical bleeding, and facilitates tissue divulsion. This prospective, randomised, blind study evaluated the use of TA in bitches submitted to mastectomy and compared the effect of TA with an intravenous fentanyl bolus. A 2.5-mcg/kg intravenous fentanyl bolus (n = 10) was compared with TA using 0.275% lidocaine (n = 10) in bitches submitted to unilateral mastectomy. Sedation was performed by intramuscular (IM) injection of 0.05 mg/kg of acepromazine combined with 2 mg/kg of meperidine. Anaesthesia was induced with 5 mg/kg of intravenous propofol and maintained with isoflurane/O2. Heart and respiratory rates; systolic, mean, and diastolic arterial blood pressures; central venous pressure; SpO2; ETCO2; inspired and expired isoflurane concentrations; and temperature were measured transoperatively. Visual analogue scales for sedation and pain and the Glasgow composite and Melbourne pain scales were used for postoperative assessment. The surgeon investigated the quality of the surgical approach, considering bleeding and resection ability, and the incidence of postoperative wound complications.

RESULTS

The heart rate was lower and the end-tidal isoflurane concentration was higher in dogs treated with fentanyl than in dogs treated with TA. A fentanyl bolus was administered to 8 of 10 dogs treated with fentanyl and to none treated with TA. Intraoperative bleeding and the mammary gland excision time were lower in dogs treated with TA. The maximal mean and individual plasma lidocaine concentrations were 1426 ± 502 ng/ml and 2443 ng/ml at 90 minutes after infiltration, respectively. The Glasgow Composite Pain Scale scores were higher in dogs treated with fentanyl than in dogs treated with TA until 2 hours after extubation.

CONCLUSIONS

Compared with intravenous fentanyl, TA in bitches: may be easily performed in non-inflamed, ulcerated, adhered mammary tumours; has an isoflurane-sparing effect; improves transoperative and immediate postoperative analgesia; is apparently safe for use in clinical conditions as evidenced by the fact that it did not produce any adverse signs or lidocaine plasma concentrations compatible with toxicity; does not modify the recovery time; and facilitates the surgical procedure without interfering with wound healing.