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

Pharmacokinetics of a continuous intravenous infusion of hydromorphone in healthy dogs

Introduction

Dosing recommendations for hydromorphone intravenous constant rate infusion (IV CRI) are derived from simulations following IV bolus administration. While this extrapolated dose regimen has been described clinically, pharmacokinetics (PK) of hydromorphone infusions in dogs are not yet described. The study objective was to describe the PK of hydromorphone in healthy dogs receiving an IV bolus followed by an IV CRI for 48 h.

Methods

A prospective, experimental study was performed involving the administration of hydromorphone (0.1 mg/kg IV bolus then IV CRI 0.01 mg/kg/h over a 48 h period) to 6 healthy Beagle dogs. Blood samples were collected at 16 time points between 0 and 58 h relative to the initial bolus. Plasma hydromorphone concentrations were analyzed by high pressure liquid chromatography with tandem mass spectrometry detection. Pharmacokinetic parameter estimates were obtained with compartmental methods using commercially available software.

Results

A two-compartment model with first order elimination was used. At the end of the infusion, median (range) plasma hydromorphone concentrations were 6.8 (5.5-19.6) ng/mL. The median total body clearance was 30.4 (19.8-36.7) mL/min/kg; volume of distribution at steady state was 4.5 (3.2-7.8) L/kg; and terminal elimination half-life was 11.2 (7.6-24.3) h.

Conclusion

Hydromorphone (0.1 mg/kg IV bolus then IV CRI of 0.01 mg/kg/h) maintained steady-state plasma concentrations above the minimum human analgesic target in healthy Beagle dogs with minimal side effects. Further studies are needed to determine the effective plasma concentrations of hydromorphone in painful dogs.

An Examination of the Complex Pharmacological Properties of the Non-Selective Opioid Modulator Buprenorphine

The goal of this review is to provide a recent examination of the pharmacodynamics as well as pharmacokinetics, misuse potential, toxicology, and prenatal consequences of buprenorphine. Buprenorphine is currently a Schedule III opioid in the US used for opioid-use disorder (OUD) and as an analgesic. Buprenorphine has high affinity for the mu-opioid receptor (MOR), delta (DOR), and kappa (KOR) and intermediate affinity for the nociceptin (NOR). Buprenorphine's active metabolite, norbuprenorphine, crosses the blood-brain barrier, is a potent metabolite that attenuates the analgesic effects of buprenorphine due to binding to NOR, and is responsible for the respiratory depressant effects. The area under the concentration curves are very similar for buprenorphine and norbuprenorphine, which indicates that it is important to consider this metabolite. Crowding sourcing has identified a buprenorphine street value (USD 3.95/mg), indicating some non-medical use. There have also been eleven-thousand reports involving buprenorphine and minors (age < 19) at US poison control centers. Prenatal exposure to clinically relevant dosages in rats produces reductions in myelin and increases in depression-like behavior. In conclusion, the pharmacology of this OUD pharmacotherapy including the consequences of prenatal buprenorphine exposure in humans and experimental animals should continue to be carefully evaluated.

The Outcomes of an Opioid-Free Anaesthetic Plan in Fourteen Dogs Undergoing Enucleation Using an Ultrasound-Guided Supra-Temporal Retrobulbar Block: A Retrospective Case Series

The objective of this retrospective case series is to report the outcomes of an opioid-free anesthetic plan in dogs undergoing enucleation surgery. A total of 14 dogs were admitted for enucleation between March and December 2020. A multimodal approach to perioperative analgesia was used, with a focus on retrobulbar anesthesia. A combination of an ultrasound-guided retrobulbblock with a supratemporal approach in association with ketamine, dexmedetomidine and non-steroidal anti-inflammatory drugs was used in the reported cases. Intraoperative nociception was defined as an increase of 20% from the baseline in one or more of the following parameters: heart rate, respiratory rate or mean arterial pressure. An ultrasound-guided retrobulbar block in an opioid-free anesthesia regime was effective at managing the perioperative analgesia of 13 out of 14 dogs. In only one case, a bolus of fentanyl was administered to treat intraoperative nociception. Recovery was uneventful in all the dogs, and the postoperative pain scores remained below the intervention threshold at all time points. To the authors' knowledge, this is the first reported case series of opioid-free anesthesia for enucleation in dogs.

Medication safety education: more than just a human concern?

The medication misuse epidemic continues to be a major concern for both human and veterinary health-care providers. Medication misuse of veterinary prescribed drugs is contributing to the public health crisis. Education of students regarding appropriate prescribing, communication with clients about medication storage, recognition of signs of vet shopping and animal abuse, and appropriate pain management strategies are essential steps for ensuring our students are prepared for the world that awaits them outside the halls of academic veterinary medicine. This is the moment where veterinarians can make a difference in the lives of patients, students, and the public health.

The analgesic and sedative effects of GV20 pharmacopuncture with low-dose hydromorphone in healthy dogs undergoing ovariohysterectomy

This study evaluates the analgesic efficacy of low-dose hydromorphone administered via pharmacopuncture at Governing Vessel 20 (GV20) for postoperative pain management following canine ovariohysterectomy. Fifty clinically healthy female dogs undergoing ovariohysterectomy were allocated to receive hydromorphone [0.1 mg/kg body weight (BW)] intramuscularly (IM, n = 25) or hydromorphone (0.01 mg/kg BW) pharmacopuncture at GV20 (GV, n = 25) following extubation. This was a prospective, blinded, randomized clinical trial. Pain and sedation scores were evaluated using the Glasgow Composite Measure Pain Scale Short Form (CMPS-SF) at 1, 2, 3, 4, and 12 hours following study treatment. Time of treatment failure (CMPS-SF ≥ 6/24) was recorded and analyzed using Kaplan-Meier survival analysis. Patient demographics and duration of surgery and anesthesia were analyzed using the appropriate unpaired Student's t-test. The Glasgow CMPS-SF and sedation score were analyzed using a repeated measures 2-way analysis of variance (ANOVA) followed by Bonferroni post-test where appropriate. Significance was set a P < 0.05. There were no significant differences in patient demographics, anesthesia and surgery duration, and study treatment failure. The Glasgow CMPS-SF scores were significantly higher for IM compared with GV [2 (0 to 8) versus 1 (0 to 6), respectively; P = 0.044] at 4 hours. Sedation scores were significantly higher for IM compared with GV at 2 [2 (1 to 3) and 1 (1 to 3), respectively; P = 0.0004] and 4 [1 (1 to 3) and 1 (1 to 2), respectively; P = 0.03] hours. Pharmacopuncture with low-dose hydromorphone provided adequate postoperative analgesia in dogs undergoing ovariohysterectomy with reduced sedative effects. Pharmacopuncture is a good alternative in dogs when reduced dosing of opioids is recommended.

Clinical Pharmacology, Toxicity, and Abuse Potential of Opioids

Opioids were the most common drug class resulting in overdose deaths in the United States in 2019. Widespread clinical use of prescription opioids for moderate to severe pain contributed to the ongoing opioid epidemic with the subsequent emergence of fentanyl-laced heroin. More potent analogues of fentanyl and structurally diverse opioid receptor agonists such as AH-7921 and MT-45 are fueling an increasingly diverse illicit opioid supply. Overdose from synthetic opioids with high binding affinities may not respond to a typical naloxone dose, thereby rendering autoinjectors less effective, requiring higher antagonist doses or resulting in a confusing clinical picture for health care providers. Nonscheduled opioid drugs such as loperamide and dextromethorphan are associated with dependence and risk of overdose as easier access makes them attractive to opioid users. Despite a common opioid-mediated pathway, several opioids present with unique pharmacodynamic properties leading to acute toxicity and dependence development. Pharmacokinetic considerations involve half-life of the parent opioid and its metabolites as well as resulting toxicity, as is established for tramadol, codeine, and oxycodone. Pharmacokinetic considerations, toxicities, and treatment approaches for notable opioids are reviewed.

Declines and pronounced regional disparities in meperidine use in the United States

There have been increasing concerns about adverse effects and drug interactions with meperidine. The goal of this study was to characterize meperidine use in the United States. Meperidine distribution data were obtained from the Drug Enforcement Administration's Automated of Reports and Consolidated Orders System. The Medicare Part D Prescriber Public Use File was utilized to capture overall trends in national prescriptions in this observational report. Nationally, meperidine distribution decreased by 94.6% from 2001 to 2019. In 2019, Arkansas, Alabama, Oklahoma, and Mississippi saw significantly greater distribution when compared with the US state average of 9.27 mg per 10 persons (SD = 6.82). Meperidine distribution showed an 18-fold difference between the highest state (Arkansas = 36.8 mg) and lowest state (Minnesota = 2.1 mg). Five of the six states with the lowest distribution were in the Northeast. Meperidine distribution per state was correlated with the prevalence of adult obesity (r(48) = +0.48, p < .001). Family medicine and internal medicine physicians accounted for 28.9% and 20.5%, respectively, of meperidine total daily supply (TDS) in 2017. Interventional pain management (5.66) and pain management (3.48) physicians accounted for the longest TDS per provider. The use of meperidine declined over the last two decades. Meperidine varied by geographic region with south-central states, and those with more obesity, showing greater distribution. Primary care doctors continue to account for the majority of meperidine daily supply. Increasing knowledge of meperidine's undesirable adverse effects like seizures and serious drug-drug interactions is likely responsible for these pronounced reductions.

Assessment of Controlled Substance Distribution to U.S. Veterinary Teaching Institutions From 2006 to 2019

Objective: To evaluate the changing pattern of distribution of Schedule II and III opioids, barbiturates, and stimulants to veterinary educational institutions in the United States.

Design: Longitudinal study.

Sample: Veterinary teaching institutions that use Schedule II and III drugs.

Procedures: Distribution of controlled substances to veterinary teaching institutions was obtained from the Drug Enforcement Administration's Automated Reports and Consolidated Orders System (ARCOS) for opioids (e.g., methadone, fentanyl, codeine), barbiturates (pentobarbital, butalbital), and stimulants (amphetamine, methylphenidate, lisdexamfetamine) from 2006–2019. Opioids were converted to their morphine milligram equivalents (MME) for evaluation over time.

Results: Controlled substance distribution to veterinary schools exhibited dynamic, and agent specific, changes. The total MME for 11 opioids peaked in 2013 and decreased by 17.3% in 2019. Methadone accounted for two-fifths (42.3%) and fentanyl over one-third (35.4%) of the total MME in 2019. Pentobarbital distribution was greatest by weight of all substances studied and peaked in 2011 at 69.4 kg. Stimulants underwent a pronounced decline and were very modest by 2014.

Conclusions and Clinical Relevance: Opioids by total MME in veterinary teaching practice have undergone more modest changes than opioids used with humans. Hydrocodone, codeine and recently fentanyl use have declined while methadone increased. Stimulant distribution decreased to become negligible. Together, this pattern of findings warrant continued monitoring.