Human pharmacokinetics of intravenous, sublingual, and buccal buprenorphine

Salivary Therapeutic Monitoring of Buprenorphine in Neonates After Maternal Sublingual Dosing Guided by Physiologically Based Pharmacokinetic Modeling

BACKGROUND

Opioid use disorder (OUD) during pregnancy is associated with high mortality rates and neonatal opioid withdrawal syndrome (NOWS). Buprenorphine, an opioid, is used to treat OUD and NOWS. Buprenorphine active metabolite (norbuprenorphine) can cross the placenta and cause neonatal respiratory depression (EC50 = 35 ng/mL) at high brain extracellular fluid (bECF) levels. Neonatal therapeutic drug monitoring using saliva decreases the likelihood of distress and infections associated with frequent blood sampling.

METHODS

An adult physiologically based pharmacokinetic model for buprenorphine and norbuprenorphine after intravenous and sublingual administration was constructed, vetted, and scaled to newborn and pregnant populations. The pregnancy model predicted that buprenorphine and norbuprenorphine doses would be transplacentally transferred to the newborns. The newborn physiologically based pharmacokinetic model was used to estimate the buprenorphine and norbuprenorphine levels in newborn plasma, bECF, and saliva after these doses.

RESULTS

After maternal sublingual administration of buprenorphine (4 mg/d), the estimated plasma concentrations of buprenorphine and norbuprenorphine in newborns exceeded the toxicity thresholds for 8 and 24 hours, respectively. However, the norbuprenorphine bECF levels were lower than the respiratory depression threshold. Furthermore, the salivary buprenorphine threshold levels in newborns for buprenorphine analgesia, norbuprenorphine analgesia, and norbuprenorphine hypoventilation were observed to be 22, 2, and 162 ng/mL.

CONCLUSIONS

Using neonatal saliva for buprenorphine therapeutic drug monitoring can facilitate newborn safety during the maternal treatment of OUD using sublingual buprenorphine. Nevertheless, the suitability of using adult values of respiratory depression EC50 for newborns must be confirmed.

Bibliometric evaluation of Journal of Analytical Toxicology as a scholarly publication according to the Web-of-Science citation database

Soon approaching its 50th anniversary, Journal of Analytical Toxicology (JAT) is an international scholarly publication specializing in analytical and forensic aspects of toxicology. Science Citation Index (SCI) and Journal Citation Reports (JCR), both of which are part of the Web-of-Science (WOS) database, were used to make a bibliometric evaluation of JAT articles. Between 1977 (volume 1) and 2023 (volume 47), a total of  n = 4,785 items were published in JAT; the top-ten most highly cited articles and the most prolific authors were identified. Changes in the journal impact factor (JIF) were studied between 1997 and 2022, and this metric varied from a low of 1.24 (2006) to a high of 3.36 (2020).The most recent JIF (2022) dropped to 2.5 and the corresponding 5 year JIF was 2.6. JAT's most highly cited article (590 cites) was a working group (SWGTOX) report dealing with standard practices for the validation of analytical methods in forensic toxicology laboratories. JAT published 62 articles each of which were cited over 100 times and the H-index for JAT was 89. The most prolific author of JAT articles was credited with 119 items, the first in 1980 (volume 4) and the latest in 2023 (volume 47). JAT articles were cited 4,537 times in 2022 by all journals in the JCR database, although 520 of these were self-citations (11.5%). Bibliometric methods are increasingly used to evaluate the published work of individual scientists, university departments, entire universities and whole countries. Highly cited articles are considered more influential and authoritative compared with papers that are seldom or never cited.

Effectiveness of Sublingual Buprenorphine for Pain Control in the ICU

OBJECTIVES

The objective of this study was to compare pain control and opioid consumption in critically ill patients who were treated with buprenorphine sublingual or oxycodone oral/enteral during ICU admission.

DESIGN

This was a retrospective, parallel, cohort study.

SETTING

General medical or surgical ICUs of a quaternary, urban hospital in Sydney, NSW, Australia.

PATIENTS

Data were obtained for all patients admitted to two general medical or surgical ICU from January 2019 to January 2023. Patients were grouped as those who received buprenorphine sublingual versus oxycodone oral/enteral.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Pain control was compared between a propensity score matched cohort of patients who received buprenorphine versus oxycodone. The primary outcome was the probability of significant pain. A significant pain score was defined as greater than or equal to 4 on the 0-10 Numeric Rating Scale or greater than or equal to 6 on the Behavioral Pain Scale. The study cohort included 1,070 patients (288 buprenorphine and 782 oxycodone). After propensity score matching, there were 288 patients in each group. The mean age of the matched cohort was 64 ± 16 years, 295 (51%) were male, and 359 (62%) had a surgical admission. The median probability of significant pain was 0.16 with buprenorphine and 0.17 with oxycodone (median difference, 0.01; 95% CI, -0.02 to 0.04; p = 0.50). Median opioid consumption in oral morphine milligram equivalents (MMEs) was 65 with buprenorphine and 70 with oxycodone (median difference, -1 mg; 95% CI, -10 to 10 mg; p = 0.73). Median MME per ICU day was 22 with buprenorphine and 22 with oxycodone (median difference, 1 mg; 95% CI, -2 to 5 mg; p = 0.38).

CONCLUSIONS

Buprenorphine sublingual is as effective as oxycodone oral/enteral with regard to pain control and opioid consumption in the ICU. Buprenorphine sublingual is an appropriate option for patients in the ICU who are unable to take oral/enteral medications.

Impact of State Laws on Dispensing Opioid Prescriptions Following Posterior Lumbar Interbody Fusion Procedures: A Retrospective Large National Database Study

STUDY DESIGN

Retrospective Cohort Study.

OBJECTIVES

This study aimed to examine the effect of state legislation on prescribing behavior after a commonly performed spinal procedure, posterior lumbar interbody fusion (PLIF).

METHODS

Two cohorts of patients from the Pearl Diver Database were created based on patients who underwent PLIF surgery in 2014-15 and 2018-19. We compared opioid prescription rates and morphine-milli-equivalent (MME) between states with and without prescription legislation.

RESULTS

We analyzed 50 958 PLIF patients from 2014-15 and 46 751 patients from 2018-19. Among them, 38 states passed opioid prescription laws in 2016-2017, while 12 states did not. The percentage of patients receiving opioid prescriptions within 365 days post-surgery remained similar in both time periods (49% in 2014-15 and 48% in 2018-2019). This trend was consistent across states with and without prescription legislation (50% vs 48% in 2014-2015, and similar in 2018-19). Opioid prescription quantity significantly decreased in all states between 2014-15 and 2018-19. In states with legislation, average MME dropped from 9198 ± 21 002 to 4932 ± 13 213 (46.4% decrease), and in states without legislation, it decreased from 9175 ± 21 032 to 4994 ± 11 687 (45.6% decrease). However, these differences were not statistically significant (P = .7985).

CONCLUSION

From 2014 to 2018, there was a significant decrease in the number of opioids prescribed after PLIF. However, this decrease occurred irrespective of state legislation on prescribing practices being passed. We believe the reduction in opioids prescribed was due to increased awareness surrounding the dangers of opioids among physicians.

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.

Low dose IV buprenorphine inductions for patients with opioid use disorder and concurrent pain: a retrospective case series

BACKGROUND

Hospitalizations are a vital opportunity for the initiation of life-saving opioid agonist therapy (OAT) for patients with opioid use disorder. A novel approach to OAT initiation is the use of IV buprenorphine for low dose induction, which allows patients to immediately start buprenorphine at any point in a hospitalization without stopping full agonist opioids or experiencing significant withdrawal.

METHODS

This is a retrospective case series of 33 patients with opioid use disorder concurrently treated with full agonist opioids for pain who voluntarily underwent low dose induction at a tertiary academic medical center. Low dose induction is the process of initiating very low doses of buprenorphine at fixed intervals with gradual dose increases in patients who recently received or are simultaneously treated with full opioid agonists. Our study reports one primary outcome: successful completion of the low dose induction (i.e. transitioned from low dose IV buprenorphine to sublingual buprenorphine-naloxone) and three secondary outcomes: discharge from the hospital with buprenorphine-naloxone prescription, self-reported pain scores, and nursing-assessed clinical opiate withdrawal scale (COWS) scores over a 6-day period, using descriptive statistics. COWS and pain scores were obtained from day 0 (prior to starting the low dose induction) to day 5 to assess the effect on withdrawal symptoms and pain control.

RESULTS

Thirty patients completed the low dose induction (30/33, 90.9%). Thirty patients (30/33, 90.9%) were discharged with a buprenorphine prescription. Pain and COWS scores remained stable over the course of the study period. Mean COWS scores for all patients were 2.6 (SD 2.8) on day 0 and 1.6 (SD 2.6) on day 5. Mean pain scores for all patients were 4.4 (SD 2.1) on day 0 and 3.5 on day 5 (SD 2.1).

CONCLUSIONS

This study found that an IV buprenorphine low dose induction protocol was well-tolerated by a group of 33 hospitalized patients with opioid use disorder with co-occurring pain requiring full agonist opioid therapy. COWS and pain scores improved for the majority of patients. This is the first case series to report mean daily COWS and pain scores over an extended period throughout a low dose induction process.

Long-acting opioids and cardiovascular diseases: Help or hindrance!

Opioids are widely being used for chronic pain management, cough and diarrhea suppressants, anesthetic agents, and opioid de-addiction therapy. Opioid receptors, present in the central nervous system and peripheral tissues, are documented to regulate several cardiac functions through different signaling pathways. Long-acting opioids (LAO) have been successfully evaluated for their beneficial effects in various cardiovascular diseases viz. myocardial infarction, ischemic reperfusion injuries, atherosclerosis etc. However, on the other hand, several research studies pointed towards the harmful effects of LAOs which are mainly associated with QTc prolongation, torsade de pointes, ventricular arrhythmias, and cardiac arrest. This review shall familiarize readers with the benefits as well as the harmful effects of long-acting opioids in cardiovascular diseases. We have also provided an overview of cardiac opioid receptors, endogenous cardiac opioid peptides, and regulation of cardiovascular functions by central and cardiac opioid receptors.

Improving the Emergency Department Management of Sickle Cell Vaso-Occlusive Pain Crisis: The Role and Options of Sublingual and Intranasally Administered Analgesia

Vaso-occlusive crisis (VOC), characterized by periods of excruciating pain is the most common clinical manifestation of sickle cell disease (SCD), often resulting in emergency room presentation. These patients often experience long wait times in the emergency department before receiving their first dose of analgesia. This delay results from the complexities of the emergency care system. Using the intranasal or sublingual approach to administering analgesia to SCD patients with VOC offers a fast, safe, noninvasive, atraumatic, and easily accessible route of administration which could reduce the time to first dose of analgesia. With the evolving advances in the development and delivery of analgesic medications, providers should be conversant with the nuances of intranasal and sublingual analgesia in the management of acute vaso-occlusive pain crisis. This review explores the pharmacokinetic profiles, dosages, and administration of intranasal and sublingual analgesics with relevance to the SCD population.

How Would You Treat This Patient With Acute and Chronic Pain From Sickle Cell Disease? : Grand Rounds Discussion From Beth Israel Deaconess Medical Center

Sickle cell disease is prevalent in large numbers of patients in the United States and has a significant global impact. Its complications span numerous organs and lead to reduced life expectancy. Acute and chronic sickle cell pain is a common cause of patient suffering. The American Society of Hematology published updated guidelines on management of acute and chronic pain from sickle cell disease in 2019. Several of the recommendations are conditional and leave specific decisions to the treating physician. These include conditional recommendations about the use of ketamine for acute pain and the initiation and discontinuation of long-term opioid therapy for chronic pain. Here, 2 hematologists discuss these guidelines and make contrasting recommendations for the management of acute and chronic pain for a patient with sickle cell disease.

Effects of Buprenorphine Dose and Therapeutic Engagement on Illicit Opiate Use in Opioid Use Disorder Treatment Trials

The impact of agonist dose and of physician, staff and patient engagement on treatment have not been evaluated together in an analysis of treatment for opioid use disorder. Our hypotheses were that greater agonist dose and therapeutic engagement would be associated with reduced illicit opiate use in a time-dependent manner. Publicly-available treatment data from six buprenorphine efficacy and safety trials from the Federally-supported Clinical Trials Network were used to derive treatment variables. Three novel predictors were constructed to capture the time weighted effects of buprenorphine dosage (mg buprenorphine per day), dosing protocol (whether physician could adjust dose), and clinic visits (whether patient attended clinic). We used time-in-trial as a predictor to account for the therapeutic benefits of treatment persistence. The outcome was illicit opiate use defined by self-report or urinalysis. Trial participants (N = 3022 patients with opioid dependence, mean age 36 years, 33% female, 14% Black, 16% Hispanic) were analyzed using a generalized linear mixed model. Treatment variables dose, Odds Ratio (OR) = 0.63 (95% Confidence Interval (95%CI) 0.59−0.67), dosing protocol, OR = 0.70 (95%CI 0.65−0.76), time-in-trial, OR = 0.75 (95%CI 0.71−0.80) and clinic visits, OR = 0.81 (95%CI 0.76−0.87) were significant (p-values < 0.001) protective factors. Treatment implications support higher doses of buprenorphine and greater engagement of patients with providers and clinic staff.

Physiologically-Based Pharmacokinetic Modeling to Investigate the Effect of Maturation on Buprenorphine Pharmacokinetics in Newborns with Neonatal Opioid Withdrawal Syndrome

Neonatal opioid withdrawal syndrome (NOWS) is a major public health concern whose incidence has paralleled the opioid epidemic in the United States. Sublingual buprenorphine is an emerging treatment for NOWS, but given concerns about long-term adverse effects of perinatal opioid exposure, precision dosing of buprenorphine is needed. Buprenorphine pharmacokinetics (PK) in newborns, however, is highly variable. To evaluate underlying sources of PK variability, a neonatal physiologically-based pharmacokinetic (PBPK) model of sublingual buprenorphine was developed using Simcyp (version 19.1). The PBPK model included metabolism by cytochrome P450 (CYP) 3A4, CYP2C8, UDP-glucuronosyltransferase (UGT) 1A1, UGT1A3, UGT2B7, and UGT2B17, with additional biliary excretion. Maturation of metabolizing enzymes was incorporated, and default CYP2C8 and UGT2B7 ontogeny profiles were updated according to recent literature. A biliary clearance developmental profile was outlined using clinical data from neonates receiving sublingual buprenorphine as NOWS treatment. Extensive PBPK model validation in adults demonstrated good predictability, with geometric mean (95% confidence interval (CI)) predicted/observed ratios (P/O ratios) of area under the curve from zero to infinity (AUC_0-∞ ), peak concentration (C_max ), and time to reach peak concentration (T_max ) equaling 1.00 (0.74-1.33), 1.04 (0.84-1.29), and 0.95 (0.72-1.26), respectively. In neonates, the geometric mean (95% CI) P/O ratio of whole blood concentrations was 0.75 (95% CI 0.64-0.87). PBPK modeling and simulation demonstrated that variability in biliary clearance, sublingual absorption, and CYP3A4 abundance are likely important drivers of buprenorphine PK variability in neonates. The PBPK model could be used to guide development of improved buprenorphine starting dose regimens for the treatment of NOWS.

Oxidative Stress Indices Changes in the Hearts of Rat Pups in Response to Maternal Buprenorphine Treatment during Gestation and Lactation

This study aimed to assess the effects of Buprenorphine (BUP) on oxidative parameters in pups born to mothers exposed to the drug during gestation and lactation. Pregnant and lactating rats received BUP, 0.5 or 0.1 mg/kg subcutaneously for 21 and 28 days, respectively. At the end of the study, the pups were anesthetized, and the hearts were dissected out to measure oxidative stress indices, including the levels of Malondialdehyde (MDA), Nitric oxide (NO), Glutathione (GSH), and the activity of Superoxide dismutase (SOD). Our findings indicated that BUP did not alter MDA, NO, GSH levels, nor SOD activity in the cardiac tissue of pups exposed to this drug during the fetal period and through breast milk. We suggest performing additional studies to determine the association between BUP and oxidative modifications in cardiac tissues of pups born to mothers under BUP therapy during gestation and lactation.

Transdermal buprenorphine for pain management in children

Pain is one of the main symptoms reported by sick children, particularly by those suffering from cancer. Opioids are very useful in controlling this symptom but they are burdened with significant side effects that limit their use in children. Buprenorphine is a strong opioid that, due to its particular pharmacological characteristics, ensures excellent pain relief with fewer side effects than other opioids. The transdermal formulation allows for good pain control associated with optimal compliance by patients and few limitations on daily life. Unfortunately, transdermal buprenorphine use remains off-label for the control of chronic pain in children; therefore, it is desirable that new studies can validate its use in the paediatric population. This review aims to analyse the clinical advantages of transdermal buprenorphine in the paediatric population and the possible side effects registered in daily clinical practice.

In vivo and in vitro Characterization of a Partial Mu Opioid Receptor Agonist, NKTR-181, Supports Future Therapeutic Development

Mu opioid receptor (MOPr) agonists are well-known and frequently used clinical analgesics but are also rewarding due to their highly addictive and often abusive properties. This may lead to opioid use disorder (OUD) a disorder that effects millions of people worldwide. Therefore, novel compounds are urgently needed to treat OUD. As opioids are effective analgesics and OUD often occurs in conjunction with chronic pain, these novel compounds may be opioids, but they must have a low abuse liability. This could be mediated by diminishing or slowing blood-brain barrier transport, slowing target receptor binding kinetics, and showing a long half-life. NKTR-181 is a PEGylated oxycodol and a MOPr agonist that has slowed blood-brain barrier transport, a long half-life, and diminished likeability in clinical trials. In this study, we examined the signaling and behavioral profile of NKTR-181 in comparison with oxycodone to determine whether further therapeutic development of this compound may be warranted. For this preclinical study, we used a number of in vitro and in vivo assays. The signaling profile of NKTR-181 was determined by the electrophysiological assessment of MOPr-Ca2+ channel inhibition in the nociceptive neurons of rodent dorsal root ganglia. Heterologous cell-based assays were used to assess biased agonism and receptor trafficking. Different rodent behavioral models were used to define the NKTR-181-induced relief of effective and reflexive nociception and drug-seeking behavior as assessed by an intravenous self-administration (IVSA) of NKTR-181. We found that NKTR-181 and oxycodone are partial agonists in G-protein signaling and Ca2+ channel inhibition assays and promote limited MOPr desensitization. However, NKTR-181 inhibits Ca2+ channels by a different mechanism than oxycodone and induces a different pattern of arrestin recruitment. In addition, NKTR-181 has a slower receptor on-rate and a slower rate of Ca2+ channel coupling than oxycodone. This signaling profile is coupled with a slower onset of antinociception and limited drug-seeking behavior in comparison with oxycodone. Together with its known long half-life and slow blood-brain barrier transport, these data suggest that NKTR-181 could be further studied as a pharmacotherapeutic treatment modality for OUD.

Evaluation of Drug-Drug Interaction Liability for Buprenorphine Extended-Release Monthly Injection Administered by Subcutaneous Route

Buprenorphine extended‐release (BUP‐XR) formulation is a once‐monthly subcutaneous injection for the treatment of opioid use disorder (OUD). Buprenorphine undergoes extensive cytochrome P450 (CYP) 3A4 metabolism, leading to potential drug‐drug interactions (DDIs) as reported for sublingual buprenorphine. Sublingual buprenorphine is subject to first‐pass extraction, as a significant proportion of the dose is swallowed. Because subcutaneous administration avoids first‐pass extraction, the DDI with CYP3A4 inhibitors is expected to be less than the 2‐fold increase reported for the sublingual route. The objective of this analysis was to predict the magnitude of DDI following coadministration of BUP‐XR with a strong CYP3A4 inhibitor or inducer using physiologically based pharmacokinetic (PBPK) modeling. Models were developed and verified by comparing predicted and observed data for buprenorphine following intravenous and sublingual dosing. Comparison of predicted and observed pharmacokinetic (PK) profiles and PK parameters demonstrated acceptable predictive performance of the models (within 1.5‐fold). Buprenorphine plasma concentrations following administration of a single dose of BUP‐XR (300 mg) were simulated using a series of intravenous infusions. Daily coadministration of strong CYP3A4 inhibitors with BUP‐XR predicted mild increases in buprenorphine exposures (AUC, 33%‐44%; C_max, 17‐28%). Daily coadministration of a strong CYP3A4 inducer was also associated with mild decreases in buprenorphine AUC (28%) and C_max (22%). In addition, the model predicted minimal increases in buprenorphine AUC (8%‐11%) under clinical conditions of 2 weeks’ treatment with CYP3A4 inhibitors administered after initiation of BUP‐XR. In conclusion, the PBPK predictions indicate that coadministration of BUP‐XR with strong CYP3A4 inhibitors or inducers would not result in clinically meaningful interactions.

Clinical pharmacology and dosing regimen optimization of neonatal opioid withdrawal syndrome treatments

In this paper, we review the management of neonatal opioid withdrawal syndrome (NOWS) and clinical pharmacology of primary treatment agents in NOWS, including morphine, methadone, buprenorphine, clonidine, and phenobarbital. Pharmacologic treatment strategies in NOWS have been mostly empirical, and heterogeneity in dosing regimens adds to the difficulty of extrapolating study results to broader patient populations. As population pharmacokinetics (PKs) of pharmacologic agents in NOWS become more well‐defined and knowledge of patient‐specific factors affecting treatment outcomes continue to accumulate, PK/pharmacodynamic modeling and simulation will be powerful tools to aid the design of optimal dosing regimens at the patient level. Although there is an increasing number of clinical trials on the comparative efficacy of treatment agents in NOWS, here, we also draw attention to the importance of optimizing the dosing regimen, which can be arguably equally important at identifying the optimal treatment agent.

Tapentadol, Buprenorphine, and Levorphanol for the Treatment of Neuropathic Pain: a Systematic Review

PURPOSE OF REVIEW

The objective of this systematic review is to present the available evidence for the utilization of the atypical opioids tapentadol, buprenorphine, and levorphanol for the treatment of neuropathic pain.

RECENT FINDINGS

In total, 1619 articles were retrieved of which 10 studies were included. Of 5 included studies pertaining to tapentadol, 4 studies show tapentadol monotherapy to be effective for the treatment of diabetic peripheral neuropathy or chronic, radiating low back pain. Of the 3 studies included for buprenorphine, only one was a randomized controlled trial found not to have a statistically significant reduction in pain with TD buprenorphine likely due to very high withdrawal rates during the trial. Only 2 case reports were included from the available literature for levorphanol providing low-quality anecdotal evidence. The role of tapentadol, buprenorphine, and levorphanol for neuropathic pain conditions requires robust research including randomized controlled trials to evaluate their efficacy and safety.

Opioid Treatment for Neonatal Opioid Withdrawal Syndrome: Current Challenges and Future Approaches

Chronic intrauterine exposure to psychoactive drugs often results in neonatal opioid withdrawal syndrome (NOWS). When nonpharmacologic measures are insufficient in controlling NOWS, morphine, methadone, and buprenorphine are first-line medications commonly used to treat infants with NOWS because of in utero exposure to opioids. Research suggests that buprenorphine may be the leading drug therapy used to treat NOWS when compared with morphine and methadone. Currently, there are no consensus or standardized treatment guidelines for medications prescribed for NOWS. Opioids used to treat NOWS exhibit large interpatient variability in pharmacokinetics (PK) and pharmacodynamic (PD) response in neonates. Organ systems undergo rapid maturation after birth that may alter drug disposition and exposure for any given dose during development. Data regarding the PK and PD of opioids in neonates are sparse. Pharmacometric methods such as physiologically based pharmacokinetic and population pharmacokinetic modeling can be used to explore factors predictive of some of the variability associated with the PK/PD of opioids in newborns. This review discusses the utility of pharmacometric techniques for enhancing precision dosing in infants requiring opioid treatment for NOWS. Applying these approaches may contribute to optimizing the outcome by reducing cumulative drug exposure, mitigating adverse drug effects, and reducing the burden of NOWS in neonates.

High-Performance Liquid Chromatography-Tandem Mass Spectrometry for Buprenorphine Evaluation in Plasma-Application to Pharmacokinetic Studies in Rabbits

The precise and reliable determination of buprenorphine concentration is fundamental in certain medical or research applications, particularly in pharmacokinetic studies of this opioid. The main challenge is, however, the development of an analytical method that is sensitive enough, as the detected in vivo concentrations often fall in very low ranges. Thus, in this study we aimed at developing a sensitive, repeatable, cost-efficient, and easy HPLC analytical protocol for buprenorphine in rabbit plasma. In order to obtain this, the HPLC-MS² system was used to elaborate and validate the method for samples purified with liquid-liquid extraction. Fragment ions 468.6→396.2 and 468.6→414.2 were monitored, and the method resulted in a high repeatability and reproducibility and a limit of quantification of 0.25 µg/L with a recovery of 98.7–109.0%. The method was linear in a range of 0.25–2000 µg/L. The suitability of the analytical procedure was tested in rabbits in a pilot pharmacokinetic study, and it was revealed that the method was suitable for comprehensively describing the pharmacokinetic profile after buprenorphine intravenous administration at a dose of 300 µg/kg. Thus, the method suitability for pharmacokinetic application was confirmed by both the good validation results of the method and successful in vivo tests in rabbits.

Pharmacokinetic Characterization and External Evaluation of a Quantitative Framework of Sublingual Buprenorphine in Patients with an Opioid Disorder in Puerto Rico

Background: The aim of this analysis was to characterize the pharmacokinetics (PK) of sublingual buprenorphine (BUP) and its metabolites (buprenorphine glucuronide; BUP-g, norbuprenorphine; Nor-BUP, and norbuprenorphine glucuronide; Nor-BUP-g) in opioid use disorder (OUD) patients in Puerto Rico (PR) as a first step of evidence-based BUP dosing strategies in this population. Methods: BUP and metabolites concentrations were measured from 0 to 8 h after the administration of sublingual buprenorphine/naloxone films in 12 stable OUD subjects. Results: PK non-compartmental characteristics showed considerable variability in parameters between the subjects over the 8-h sampling time (t_max = 1.5 ± 0.7 h, C_o = 1.6 ± 1.4 ng/mL, C_max= 7.1 ± 6 ng/mL, and AUC_0–8h = 26.8 ± 17.8 h·ng/mL). Subjects had a significantly higher tendency towards CYP-mediated N-demethylation, with the AUC_0–8h ratios of the molar concentrations of [Nor-BUP + Nor-BUP-g] to BUP being (3.4 ± 1.9) significantly higher compared with BUP-g to BUP (0.19 ± 0.2). A two-compartment population-PK model with linear absorption (k_a = 2.54 h⁻¹), distribution (k₁₂= 2.34 h⁻¹, k₁₄ = 1.29 h⁻¹), metabolism (k₂₄ = 1.28 × 10⁻¹ h⁻¹, k₂₃ = 6.43 × 10⁻² h⁻¹, k₃₅ = 1.23 × 10⁻¹ h⁻¹, k₄₅ = 8.73 × 10⁻¹ h⁻¹), and elimination (k₃₀ = 3.81 × 10⁻³ h⁻¹, k₅₀ = 1.27 × 10⁻¹ h⁻¹) adequately described the time-course of BUP and its metabolites, which has been externally validated using published data. Conclusions: Although limited in sampling time and number of recruited subjects, this study presents specific BUP PK characteristics that evidenced the need for additional PK studies and subsequent modeling of the data for the development of evidence-based dosing approaches in Puerto Rico.

Buprenorphine Prevalence in DUID Cases in Southwestern Virginia: Case Studies and Observations

Buprenorphine, a semisynthetic mixed agonist/antagonist opioid used primarily for the treatment of opioid use disorder, was reported in 194 driving under the influence of drugs (DUID) cases in Southwestern Virginia during the period of 2017 through 2019. Identifying and confirming buprenorphine in DUID cases is common in this region. Interpretation is complex due to the large range of concentrations of buprenorphine found in blood and frequent combinations with other therapeutic and abused drugs. Buprenorphine was identified by immunoassay and quantified by liquid chromatography-tandem mass spectrometry (LC-MS-MS). A sensitive method was necessary as one-third of concentrations of buprenorphine and/or norbuprenorphine were less than 1.0 µg/L. Concentrations of buprenorphine ranged from < 0.5 µg/L to 11 µg/L (mean 2.5 µg/L, median 1.8 µg/L) and concentrations of norbuprenorphine ranged from < 0.5 µg/L to > 20 µg/L (mean 3.3 µg/L, median 2.2 µg/L). Buprenorphine polysubstance use was common. Only 10% of cases examined did not contain other drugs confirmed in routine DUID screening tests. The most common drug groups confirmed were benzodiazepines, amphetamines and cannabinoids. The DUID case histories presented represent examples of buprenorphine abuse, buprenorphine with no other drug groups, buprenorphine combined with other drug groups, cases consistent with impairment and cases with minimal impairment. Central nervous system depressant and narcotic analgesic symptoms were commonly observed; however, some cases contained stimulant symptoms. Buprenorphine to norbuprenorphine ratios (B/NB) had a mean and median ratio of 1.1 and 0.8, respectively. B/NB ratios greater than 3.0 were found in 4.7% of cases. The finding of a higher B/NB ratio may indicate a more recent buprenorphine administration and a greater potential for impairment. No relationship between the concentration of buprenorphine and/or norbuprenorphine in blood and performance on Drug Recognition Expert (DRE) evaluation or Standardized Field Sobriety Tests (SFST) could be determined.

Pharmacotherapy of neonatal opioid withdrawal syndrome: a review of pharmacokinetics and pharmacodynamics

INTRODUCTION

Neonatal opioid withdrawal syndrome (NOWS) often arises in infants born to mothers who used opioids during pregnancy. Morphine, methadone, and buprenorphine are the most common first-line treatments, whereas clonidine and phenobarbital are generally reserved for adjunctive therapy. These drugs exhibit substantial pharmacokinetic (PK) and pharmacodynamic (PD) variability. Current pharmacological treatments for NOWS are based on institutional protocols and largely rely on empirical treatment of patient symptoms.

AREAS COVERED

This article reviews the PK/PD of NOWS pharmacotherapies with a focus on the implication of physiological development and maturation. Body size-standardized clearance is consistently low in neonates, except for methadone. This can be ascribed to underdeveloped metabolic and elimination pathways. The effects of pharmacogenetics have been clarified especially for morphine. The PK/PD relationship of medications used in the treatment of NOWS is generally understudied.

EXPERT OPINION

Providing an appropriate opioid dose in neonates is challenging. Advancements in quantitative pharmacology and PK/PD modeling approaches facilitate identification of key factors driving PK/PD variability and characterization of exposure-response relationships. PK/PD model-informed simulations have been widely employed to define age-appropriate pediatric dosing regimens. The model-informed approach holds promise to aid more rational use of medications in the treatment of NOWS.

Effect of Sleeve Gastrectomy on Buprenorphine Pharmacokinetics: A Planned Case Observation

PURPOSE

Bariatric surgery may affect the absorption and metabolism of drugs by various mechanisms. We present a planned case observation of a patient treated with sublingual buprenorphine in an opioid maintenance treatment program, and the observed changes in buprenorphine pharmacokinetics following gastric sleeve surgery.

METHODS

Serial blood samples during a dose interval of 24 hours were obtained approximately 1 year preoperatively as well as 1 week, 1 month and 12 months postoperatively and key pharmacokinetic variables were calculated.

FINDINGS

The systemic exposure of buprenorphine (AUC) was relatively stable from the preoperative sampling to 1 week postoperatively (-6.3%), but declined markedly at 1 month (-43%) and 12 months (-42%) postoperatively. The maximum concentration of buprenorphine almost doubled at 1 week postoperatively before returning to baseline values 1 month and 12 months postoperatively.

IMPLICATIONS

This case observation indicates that after sleeve gastrectomy, the systemic exposure of sublingual buprenorphine can decrease. Clinicians should be aware of the possibility of loss of effect and emerging abstinence symptoms following sleeve gastrectomy. We recommend monitoring the patient closely for abstinence symptoms postoperatively and considering measuring serum concentrations of buprenorphine pre- and postoperatively.

Opioid and neuroHIV Comorbidity - Current and Future Perspectives

With the current national opioid crisis, it is critical to examine the mechanisms underlying pathophysiologic interactions between human immunodeficiency virus (HIV) and opioids in the central nervous system (CNS). Recent advances in experimental models, methodology, and our understanding of disease processes at the molecular and cellular levels reveal opioid-HIV interactions with increasing clarity. However, despite the substantial new insight, the unique impact of opioids on the severity, progression, and prognosis of neuroHIV and HIV-associated neurocognitive disorders (HAND) are not fully understood. In this review, we explore, in detail, what is currently known about mechanisms underlying opioid interactions with HIV, with emphasis on individual HIV-1-expressed gene products at the molecular, cellular and systems levels. Furthermore, we review preclinical and clinical studies with a focus on key considerations when addressing questions of whether opioid-HIV interactive pathogenesis results in unique structural or functional deficits not seen with either disease alone. These considerations include, understanding the combined consequences of HIV-1 genetic variants, host variants, and μ-opioid receptor (MOR) and HIV chemokine co-receptor interactions on the comorbidity. Lastly, we present topics that need to be considered in the future to better understand the unique contributions of opioids to the pathophysiology of neuroHIV.

Graphical Abstract

Physiologically-Based Pharmacokinetic (PBPK) Modeling of Buprenorphine in Adults, Children and Preterm Neonates

Buprenorphine plays a crucial role in the therapeutic management of pain in adults, adolescents and pediatric subpopulations. However, only few pharmacokinetic studies of buprenorphine in children, particularly neonates, are available as conducting clinical trials in this population is especially challenging. Physiologically-based pharmacokinetic (PBPK) modeling allows the prediction of drug exposure in pediatrics based on age-related physiological differences. The aim of this study was to predict the pharmacokinetics of buprenorphine in pediatrics with PBPK modeling. Moreover, the drug-drug interaction (DDI) potential of buprenorphine with CYP3A4 and P-glycoprotein perpetrator drugs should be elucidated. A PBPK model of buprenorphine and norbuprenorphine in adults has been developed and scaled to children and preterm neonates, accounting for age-related changes. One-hundred-percent of the predicted AUC_last values in adults (geometric mean fold error (GMFE): 1.22), 90% of individual AUC_last predictions in children (GMFE: 1.54) and 75% in preterm neonates (GMFE: 1.57) met the 2-fold acceptance criterion. Moreover, the adult model was used to simulate DDI scenarios with clarithromycin, itraconazole and rifampicin. We demonstrate the applicability of scaling adult PBPK models to pediatrics for the prediction of individual plasma profiles. The novel PBPK models could be helpful to further investigate buprenorphine pharmacokinetics in various populations, particularly pediatric subgroups.

A meta-analysis of the potential antidepressant effects of buprenorphine versus placebo as an adjunctive pharmacotherapy for treatment-resistant depression

BACKGROUND

Numerous reports have suggested that buprenorphine may have antidepressant effects. Many individuals with depressive disorders don't respond to first-line treatment and are classified with treatment-resistant depression (TRD). Novel therapies for depression are required to better treat this population. This meta-analysis of randomized placebo-controlled trials sought to evaluate the potential antidepressant effects of buprenorphine as an adjunctive pharmacological treatment for individuals with TRD.

METHODS

PubMed, Embase, CINAHL, Web of Science, and ClinicalTrials.gov databases were searched until June 2019 for original peer-reviewed reports of buprenorphine used for the treatment of depression. Standardized mean differences (SMD) were generated from random effects models. Risk of publication bias was assessed using a funnel plot. Potential sources of heterogeneity were explored in subgroup analyses.

RESULTS

In six studies that met inclusion criteria, depression symptom severity in individuals with TRD was not significantly decreased after an adjunctive intervention with buprenorphine when compared to placebo (SMD = -0.07, 95% CI: -0.21-0.06, p = 0.30). Five of the six studies utilized a combination of buprenorphine/samidorphan. In these studies, depression symptom severity was also not significantly reduced after intervention compared to placebo (SMD = -0.08, 95% CI: -0.21 - 0.05, p = 0.23).

LIMITATIONS

Five included studies were performed by the same research group with significant conflicts of interest.

CONCLUSIONS

This meta-analysis did not reveal a significant reduction in depression symptom severity in individuals with TRD after an adjunctive intervention with buprenorphine when compared to placebo. However, more optimal doses of buprenorphine (2 mg/day) and longer treatment lengths should be explored.

Scalable in silico Simulation of Transdermal Drug Permeability: Application of BIOiSIM Platform

INTRODUCTION

Transdermal drug delivery is gaining popularity as an alternative to traditional routes of administration. It can increase patient compliance because of its painless and noninvasive nature, aid compounds in bypassing presystemic metabolic effects, and reduce the likelihood of adverse effects through decreased systemic exposure. In silico physiological modeling is critical to predicting dermal exposure for a therapeutic and assessing the impact of different formulations on transdermal disposition.

METHODS

The present study aimed at developing a physiologically based transdermal platform, "BIOiSIM", that could be globally applied to a wide variety of compounds to predict their transdermal disposition. The platform integrates a 16-compartment model of compound pharmacokinetics and was used to simulate and predict drug exposure of three chemically and biologically distinct drug-like compounds. Machine learning optimization was composed of two components: exhaustive search algorithm (coarse-tuning) and descent (fine-tuning) integrated with the platform used to quantitatively determine parameters influencing pharmacokinetics (eg permeability, kperm) of test compounds.

RESULTS

The model successfully predicted drug exposure (AUC, Cmax and Tmax) following transdermal application of morphine, buprenorphine and nicotine in human subjects, mostly with less than two-fold absolute average fold error (AAFE). The model was further able to successfully characterize the relationship between observed systemic exposure and intended pharmacological effect. The predicted systemic concentration of morphine and plasma levels of endogenous pain biomarkers were used to estimate the effectiveness of a given therapeutic regimen.

CONCLUSION

BIOiSIM marks a novel approach to in silico prediction that will enable leveraging of machine learning technology in the pharmaceutical space. The approach to model development outlined results in scalable, accurate models and enables the generation of large parameter/coefficient datasets from in vivo clinical data that can be used in future work to train quantitative structure activity relationship (QSAR) models for predicting likelihood of compound utility as a transdermally administered therapeutic.

A Practical Approach for the Management of the Mixed Opioid Agonist-Antagonist Buprenorphine During Acute Pain and Surgery

The use of buprenorphine, a mixed opioid agonist-antagonist, for the management of chronic pain and/or opioid use disorder is increasing. As such, medical providers will more frequently encounter patients on this therapy. In this paper, we synthesize existing knowledge (derived through keyword searches using MEDLINE databases) in a novel conceptual framework for patients on buprenorphine presenting with acute pain or for those requiring surgical or invasive procedures. This framework is based on three unique domains: the patient, the features of the acute pain insult, and the environment. We discuss important considerations regarding the unique aspects of buprenorphine formulations and dosing, and we describe the importance of multidisciplinary planning and multimodal analgesic strategies. We also highlight important differences in management strategies based upon the presence or absence of opioid use disorder. All medical providers must be prepared to guide the patient on buprenorphine safely through the acute care episode, which includes adequate treatment of acute pain and avoidance of iatrogenic harm, including both short-term complications (eg, respiratory depression) and long-term complications (eg, relapse to opioid use).

Buprenorphine Pharmacology Review: Update on Transmucosal and Long-acting Formulations

: Buprenorphine is an effective treatment for opioid use disorder. As a high-affinity, partial agonist for the mu-opioid receptor, buprenorphine suppresses opioid withdrawal and craving, reduces illicit opioid use, and blocks exogenous opioid effects including respiratory depression. Other pharmacologic benefits of buprenorphine are its superior safety profile compared with full opioid agonists and its long half-life that allows daily or less-than-daily dosing. New and innovative buprenorphine formulations, with pharmacokinetic profiles that differ from the original tablet formulation, continue to be developed. These include higher bioavailability transmucosal tablets and films and also 6-month implantable and monthly injectable products. This growing array of available formulations allows more choices for patients and increased opportunity for clinicians to individualize treatment; thus, it is important for buprenorphine prescribers to understand these differences.

Buprenorphine to reverse respiratory depression from methadone overdose in opioid-dependent patients: a prospective randomized trial

Background

Naloxone is the usual drug used in opioid-induced respiratory depression but it has a short half-life, precipitates withdrawal in dependent patients, and thus for persistent reversal of long-acting opioids has to be given by titrated doses and infusions. The partial agonist buprenorphine has a much longer duration of action and causes less severe withdrawal, but still should largely reverse respiratory depression induced by full agonist opioids. We aimed to compare the efficacy/safety of buprenorphine and naloxone in reversing respiratory depression in methadone-poisoned opioid-dependent patients.

Methods

Patients with methadone-induced respiratory depression were randomized to receive naloxone (titrated doses), or lower or higher doses of buprenorphine (10 μg/kg or 15 μg/kg). The primary outcome was immediate reversal of respiratory depression. We also recorded acute opioid withdrawal, need for intubation/recurrent apnea, repeated doses of opioid antagonists, length of hospital stay, other morbidity, and mortality. The study was registered with the Iranian Registry of Clinical Trials (Trial ID: 18265; Approval code: IRCT2015011020624N1).

Results

Eighty-five patients were randomized; 55/56 patients who received buprenorphine had rapid reversal of respiratory depression, which persisted for at least 12 h. Naloxone was effective in 28/29 patients, but often required very high titrated doses (thus delaying time to respond) and prolonged infusions. Intubation (8/29 vs 5/56) and opioid withdrawal (15/29 vs 7/56) were less common with buprenorphine. There were no serious complications or deaths in those receiving buprenorphine. The 15-μg/kg buprenorphine dose appeared to provide a longer duration of action, but precipitated withdrawal more frequently than the 10-μg/kg dose.

Conclusion

Buprenorphine appears to be a safe and effective substitute for naloxone in overdosed opioid-dependent patients. Further studies are warranted to explore the optimal dosing strategy for buprenorphine to consistently maintain reversal of respiratory depression but not precipitate withdrawal.

Trial registration number

IRCT2015011020624N1. Registered 30 September 2015.

Electronic supplementary material

The online version of this article (10.1186/s13054-020-2740-y) contains supplementary material, which is available to authorized users.

Pharmacokinetics of Single Doses of Methadone and Buprenorphine in Blood and Oral Fluid in Healthy Volunteers and Correlation With Effects on Psychomotor and Cognitive Functions

PURPOSE

We aimed to study the pharmacokinetics of methadone and buprenorphine in blood and oral fluid after single-dose administration and investigate correlations between concentrations in blood and neurocognitive functions.

METHODS

A 5-way, double-blind, randomized, placebo-controlled, double-dummy, crossover study was performed to study the pharmacokinetics and neurocognitive effects of methadone (5 and 10 mg per oral) and buprenorphine (0.2 and 0.4 mg sublingual) in 22 healthy volunteers. Blood and oral fluid were collected throughout the test days, and drug concentrations in both matrices were analyzed using ultrahigh-performance liquid chromatography-tandem mass spectrometry. On-road driving testing, neurocognitive computerized tests, and subjective questionnaires were performed.

RESULTS

Large individual variations in concentrations of methadone and buprenorphine in blood and oral fluid, and accordingly oral fluid/blood drug concentration ratios, were observed. The mean ratio 6.5 hours after drug administration was 2.0 (range, 0.49-7.39) for methadone after both doses. Buprenorphine was not detected above the limit of quantification in blood after 6.5 hours. No significant correlation between methadone concentration in blood and effect was found. Significant correlations were found between buprenorphine concentration in blood and standard deviation of lateral position in the driving test and some measures of reaction time, divided attention, balance, alertness, contentedness. and sleepiness.

CONCLUSIONS

Concentrations of methadone and buprenorphine in blood and oral fluid showed large interindividual variations. No concentration-effect correlations were found for methadone, whereas low to moderate correlations were observed between buprenorphine concentration and driving, psychomotor function, and subjective rating of sleep and alertness.

Prediction of Drug-Drug Interactions Between Opioids and Overdosed Benzodiazepines Using Physiologically Based Pharmacokinetic (PBPK) Modeling and Simulation

Background

Researchers have long been interested in the potential drug–drug interactions (DDIs) between opioids and benzodiazepines. However, much remains unknown concerning the interactions between these two drug classes. The objective of this work is to study the mechanism underlying the DDIs between opioids and benzodiazepines from the perspective of their pharmacokinetic (PK) interactions. A PK interaction occurs when two drugs are metabolized by the same cytochrome P450 enzymes and is one of the most common reasons for DDIs.

Methods

We quantitatively predicted the DDIs between three opioids (fentanyl, oxycodone and buprenorphine) and four benzodiazepines (alprazolam, diazepam, midazolam and triazolam) using a physiologically based pharmacokinetic (PBPK) modeling approach. A set of PBPK models was first constructed for these common opioids and benzodiazepines using SimCYP software, and the DDIs between them were then explored at various dosages.

Results

Our simulation results suggested there were no PK interactions between normal doses of opioids and benzodiazepines; but weak interactions can be expected with the combination of opioids and overdosed benzodiazepines. Particular attention should be given to the combination of fentanyl and overdosed alprazolam since a PK interaction can be observed between them.

Conclusion

Our results appear to indicate that pharmacodynamics may play a more important role than PKs in causing DDIs between opioids and benzodiazepines. This study also demonstrated that molecular modeling can be a very useful tool to mitigate the problem of “missing metabolic reaction parameters” in PK modeling and simulation.

Electronic supplementary material

The online version of this article (10.1007/s40268-019-00282-3) contains supplementary material, which is available to authorized users.

A Narrative Pharmacological Review of Buprenorphine: A Unique Opioid for the Treatment of Chronic Pain

Buprenorphine is a Schedule III opioid analgesic with unique pharmacodynamic and pharmacokinetic properties that may be preferable to those of Schedule II full μ-opioid receptor agonists. The structure of buprenorphine allows for multimechanistic interactions with opioid receptors μ, δ, κ, and opioid receptor-like 1. Buprenorphine is considered a partial agonist with very high binding affinity for the μ-opioid receptor, an antagonist with high binding affinity for the δ- and κ-opioid receptors, and an agonist with low binding affinity for the opioid receptor-like 1 receptor. Partial agonism at the μ-opioid receptor does not provide partial analgesia, but rather analgesia equivalent to that of full μ-opioid receptor agonists. In addition, unlike full μ-opioid receptor agonists, buprenorphine may have a unique role in mediating analgesic signaling at spinal opioid receptors while having less of an effect on brain receptors, potentially limiting classic opioid-related adverse events such as euphoria, addiction, or respiratory depression. The pharmacokinetic properties of buprenorphine are also advantageous in a clinical setting, where metabolic and excretory pathways allow for use in patients requiring concomitant medications, the elderly, and those with renal or hepatic impairment. The unique pharmacodynamic and pharmacokinetic properties of buprenorphine translate to an effective analgesic with a potentially favorable safety profile compared with that of full μ-opioid receptor agonists for the treatment of chronic pain.

The unique pharmacodynamic and pharmacokinetic properties of the Schedule III opioid buprenorphine contribute to its effective pain relief and a potentially favorable safety profile for chronic pain management.

Safety And Efficacy Of The Unique Opioid Buprenorphine For The Treatment Of Chronic Pain

Background

Chronic pain is associated with decreased quality of life and is one of the most common reasons adults seek medical care, making treatment imperative for many aspects of patient well-being. Chronic pain management typically involves the use of Schedule II full μ-opioid receptor agonists for pain relief; however, the increasing prevalence of opioid addiction is a national crisis that is impacting public health and social and economic welfare. Buprenorphine is a Schedule III partial μ-opioid receptor agonist that is an equally effective but potentially safer treatment option for chronic pain than full μ-opioid receptor agonists. The purpose of this review is to provide an overview of the clinical efficacy and safety of the transdermal and buccal formulations of buprenorphine, which are approved by the Food and Drug Administration for chronic pain, compared with that of extended-release full μ-opioid receptor agonists.

Methods

Controlled or randomized controlled clinical trial information was retrieved from EMBASE, Medline, and PubMed using the search terms “buprenorphine” AND “chronic” AND “pain.”

Results

A total of 33 clinical studies were ultimately used in this review, including 29 (88%) on transdermal buprenorphine and 4 (12%) on buprenorphine buccal film. Although the measure of pain intensity varied among studies, each of these 33 trials demonstrated efficacy for buprenorphine in pain relief. A total of 28 studies also assessed safety, with each concluding that buprenorphine was generally well tolerated.

Conclusion

Comparison of current clinical data along with results of responder and safety analyses support the use of buprenorphine over full μ-opioid receptor agonists for effective preferential treatment of chronic pain; however, head-to-head clinical studies are warranted.

Retrospective Review of the Use of Transdermal Buprenorphine Patches (Butrans) in a Pediatric Population

Background: Buprenorphine is an opioid medication used for the treatment of moderate to severe pain. In Canada, buprenorphine is not indicated for use in the pediatric population and literature surrounding its use in pediatrics is limited. Our aim was to evaluate the safety of transdermal buprenorphine in a pediatric palliative care setting. Methods: Our study was performed at the IWK Health Centre. Medical records of 11 patients were examined for specific clinical characteristics. The study focused primarily on descriptive results; standard data analyses were not performed. Results: Buprenorphine was found to be well tolerated in our patient population. There were no adverse effects reported in 8 of 11 patients during their treatment with buprenorphine. The remaining 3 patients described mild adverse effects in the form of skin irritation which resolved with topical steroid treatment. Efficacy was reported as anecdotal quotes from patient records. Conclusion: In this study, the use of buprenorphine in this setting was safe in a small group of patients, with the only mild adverse effect noted being a contact dermatitis in 3 patients which resolved quickly. Other studies have also demonstrated buprenorphine to be a safe and an effective opioid for the treatment of severe pain at the end of life in a pediatric population. Given these results, the implementation of buprenorphine in pediatrics may be safe for use in patients who are unable to tolerate traditional opioid analgesic therapies.

Opioid use disorder in pregnancy

The number of pregnant people affected by the opioid epidemic in the United States continues to rise. The following key aspects of opioid use disorder in pregnancy are explored through the progression of a pregnancy via a patient case: treatment options, treatment decisions, substance use screening, dosing modifications, and other aspects of peripartum care. Many factors affect opioid use disorder treatment choices during pregnancy; however, when a pregnant person is medically eligible for a therapy and multiple options are available locally, the ultimate decision regarding treatment selection should be left up to the patient and strong support services provided. This approach to treatment results in optimal maternal and neonatal outcomes and long-term maternal engagement and retention in care.

The Pharmacokinetics and Local Tolerability of a Novel Sublingual Formulation of Buprenorphine

Aim

The principal study objective was to investigate the pharmacokinetic characteristics and determine the absolute bioavailability and tolerability of a new sublingual (SL) buprenorphine wafer.

Methods

The study was of open label, two-way randomized crossover design in 14 fasted healthy male and female volunteers. Each participant, under naltrexone block, received either a single intravenous dose of 300 mcg of buprenorphine as a constant infusion over five minutes or a sublingual dose of 800 mcg of buprenorphine in two treatment periods separated by a seven-day washout period. Blood sampling for plasma drug assay was taken on 16 occasions throughout a 48-hour period (predose and at 10, 20, 30, and 45 minutes, 1, 1.5, 2, 2.5, 3, 4, 6, 8, 12, 24 and 48 hours postdose). The pharmacokinetic parameters were determined by noncompartmental analyses of the buprenorphine plasma concentration-time profiles. Local tolerability was assessed using modified Likert scales.

Results

The absolute bioavailability of SL buprenorphine was 45.4% (95% confidence interval = 37.8-54.3%). The median times to peak plasma concentration were 10 minutes and 60 minutes after IV and SL administration, respectively. The peak plasma concentration was 2.65 ng/mL and 0.74 ng/mL after IV and SL administration, respectively. The half-lives were 9.1 hours and 11.2 hours after IV and SL administration, respectively. The wafer had very good local tolerability.

Conclusions

This novel sublingual buprenorphine wafer has high bioavailability and reduced Tmax compared with other SL tablet formulations of buprenorphine. The wafer displayed very good local tolerability. The results suggest that this novel buprenorphine wafer may provide enhanced clinical utility in the management of both acute and chronic pain.

Background

Buprenorphine is approved for use in pain management and opioid addiction. Sublingual administration of buprenorphine is a simple and noninvasive route of administration and has been available for many years. Improved sublingual formulations may lead to increased utilization of this useful drug for acute and chronic pain management.

Buprenorphine Treatment for Opioid Use Disorder: An Overview

Opioid use disorder affects over 26 million individuals worldwide. There are currently three World Health Organization-recommended and US Food and Drug Administration-approved medication treatments for opioid use disorder: the full opioid agonist methadone, the opioid partial agonist buprenorphine, and the opioid receptor antagonist naltrexone. We provide a review of the use of buprenorphine for the treatment of opioid use disorder and discuss the barriers, challenges, risks, and efficacy of buprenorphine treatment vs. other treatments. Although evidence from numerous studies has shown buprenorphine to be effective for the treatment of opioid use disorder, a majority of patients with opioid use disorder do not receive buprenorphine, or any other medical treatment. We review the different formulations of buprenorphine, including newer long-acting injectable formulations that may decrease the risk of diversion and improve adherence.

Simultaneous Transdermal Delivery of Buprenorphine Hydrochloride and Naltrexone Hydrochloride by Iontophoresis

The opioids buprenorphine hydrochloride (BUP) and naltrexone hydrochloride (NTX) show promise as a combination treatment for addiction, but no means of delivering the two compounds in one medicine currently exist. In this paper, we report sufficient input rates of both these drugs from one iontophoretic transdermal drug delivery system. Experiments were performed using dermatomed pig skin mounted in glass side-bi-side cells. BUP and NTX were iontophoretically delivered together from the anode using direct constant current from Ag/AgCl electrodes. The transdermal drug fluxes and the masses of drugs in both the stratum corneum and the underlying epidermis/dermis were measured. The apparent electroosmotic flow was quantified using a neutral marker (acetaminophen). The effects of donor composition (drug concentration/molar fraction and pH), current density and profile, and the choice of receptor solution were assessed. Iontophoresis dramatically increased the flux of both drugs compared to passive control values. Target fluxes (calculated from literature clearance values and required therapeutic plasma concentrations) were greatly exceeded for NTX and were met for BUP. The latter accumulated in the skin and suppressed electroosmotic flow, inhibiting both its own flux and that of NTX. NTX, in turn, negatively influenced the flux of BUP via co-ion competition. Lowering current density by increasing the delivery area resulted in increased electroosmotic flow but did not significantly affect current-normalized drug fluxes. Delivering the drugs from both electrodes and reversing the polarity for every 2 h did not increase the flux of either compound. In summary, during iontophoresis, BUP and NTX inhibited each other's flux by two distinct mechanisms. While the more complex behavior of BUP complicates the optimization of this drug combination, iontophoresis nevertheless appears to be a feasible approach for the controlled codelivery of NTX and BUP through the skin.

Anesthesia considerations and post-operative pain management in pregnant women with chronic opioid use

The prevalence of opioid use disorder in pregnancy has escalated markedly in recent years. Chronic opioid use during pregnancy poses several challenges for providing adequate analgesia and anesthesia in the peripartum period. These challenges include the potential for withdrawal, opioid tolerance and opioid-induced hyperalgesia. Here we discuss alterations in analgesic pharmacokinetics and pharmacodynamics that are associated with chronic opioid use. In addition, when treating pain in patients with opioid use disorder it is important to distinguish between different subgroups. In this review, we will discuss practical management strategies for parturients with (1) untreated opioid use disorder, (2) parturients on medication-assisted treatment (methadone, buprenorphine) and (3) patients recovering from opioid use disorder that are currently abstinent. Finally, we offer an overview of non-opioid strategies that may be utilized as part of a multimodal approach to providing optimal analgesia in this patient population.

Molecular Imaging of Opioid and Dopamine Systems: Insights Into the Pharmacogenetics of Opioid Use Disorders

Opioid use in the United States has steadily risen since the 1990s, along with staggering increases in addiction and overdose fatalities. With this surge in prescription and illicit opioid abuse, it is paramount to understand the genetic risk factors and neuropsychological effects of opioid use disorder (OUD). Polymorphisms disrupting the opioid and dopamine systems have been associated with increased risk for developing substance use disorders. Molecular imaging studies have revealed how these polymorphisms impact the brain and contribute to cognitive and behavioral differences across individuals. Here, we review the current molecular imaging literature to assess how genetic variations in the opioid and dopamine systems affect function in the brain's reward, cognition, and stress pathways, potentially resulting in vulnerabilities to OUD. Continued research of the functional consequences of genetic variants and corresponding alterations in neural mechanisms will inform prevention and treatment of OUD.

Approach to buprenorphine use for opioid withdrawal treatment in the emergency setting

INTRODUCTION

Opioid use disorder (OUD) is increasing in prevalence throughout the world, with approximately three million individuals in the United States affected. Buprenorphine is a medication designed, researched, and effectively used to assist in OUD recovery.

OBJECTIVE

This narrative review discusses an approach to initiating buprenorphine in the emergency department (ED) for opioid-abuse recovery.

DISCUSSION

Buprenorphine is a partial mu-opioid receptor agonist with high affinity and low intrinsic activity. Buprenorphine's long half-life, high potency, and 'ceiling effect' for both euphoric sensation and adverse effects make it an optimal treatment alternative for patients presenting to the ED with opioid withdrawal. While most commonly provided as a sublingual film or tablet, buprenorphine can also be delivered via transbuccal, transdermal, subdermal (implant), subcutaneous, and parenteral routes. Prior to ED administration, caution is recommended to avoid precipitation of buprenorphine-induced opioid withdrawal. Following the evaluation of common opioid withdrawal symptoms, a step-by-step approach to buprenorphine can by utilized to reach a sustained withdrawal relief. A multimodal medication-assisted treatment (MAT) plan involving pharmacologic treatment, as well as counseling and behavioral therapy, is essential to maintaining opioid remission. Patients may be safely discharged with safe-use counseling, close outpatient follow-up, and return precautions for continued management of their OUD. Establishing a buprenorphine program in the ED involves a multifactorial approach to establish a pro-buprenorphine culture.

CONCLUSIONS

Buprenorphine is an evidence-based, safe, effective treatment option for OUD in an ED-setting. Though successfully utilized by many ED-based treatment programs, the stigma of 'replacing one opioid with another' remains a barrier. Evidence-based discussions on the safety and benefits of buprenorphine are essential to promoting a culture of acceptance and optimizing ED OUD treatment.

Tracking narcotics consumption at a Southwestern U.S. university campus by wastewater-based epidemiology

Wastewater-based epidemiology (WBE) was applied to estimate the consumption of twelve narcotics within a Southwestern U.S. university campus. Seven consecutive 24-hour composite raw wastewater samples (n = 80) were obtained once per month from sampling locations capturing >95% of campus-generated wastewater. Samples were analyzed for indicators of consumption of morphine, codeine, oxycodone, heroin, fentanyl, methadone, buprenorphine, amphetamine, methylphenidate, alprazolam, cocaine, and MDMA using LC-MS/MS. Eleven indicator compounds (oxycodone, codeine, norcodeine, 6-acetylmorphine, EDDP, amphetamine, alprazolam, alpha-hydroxyalprazolam, cocaine, benzoylecgonine, and MDMA) occurred at 100% detection frequency across the study, followed by morphine-3-glucuronide (98%), noroxycodone (95%), methylphenidate (90%), heroin (7%), norfentanyl (7%), and fentanyl (5%). Estimates of average narcotics consumption ranked as follows in units of mg/day/1000 persons: heroin (474 ± 32), cocaine (551 ± 49), amphetamine (256 ± 12), methylphenidate (236 ± 28), methadone (72 ± 8), oxycodone (80 ± 6), alprazolam (60 ± 2), MDMA (88 ± 35), codeine (50 ± 4), and morphine (18 ± 3). This campus-based WBE study yielded baseline data on 12 narcotics for a U.S. campus and demonstrated for the first time the feasibility of detecting the fentanyl metabolite norfentanyl in this setting.

Pharmacokinetics and physiologic/behavioral effects of buprenorphine administered sublingually and intravenously to neonatal foals

Buprenorphine is absorbed following sublingual administration, which would be a low-stress delivery route in foals. However, the pharmacokinetics/pharmacodynamics are not described in foals. Six healthy foals <21 days of age participated in a blinded, randomized, 3-period, 5-sequence, 3-treatment crossover prospective study. Foals received 0.01-0.02 mg/kg buprenorphine administered SL or IV with an equivalent volume of saline administered by the opposite route. Blood was collected from the cephalic vein for pharmacokinetic analysis. Physiologic parameters (HR, RR, body temperature, GI sounds), locomotion (pedometer), and behavioral data (activity level, nursing time, response to humans) were recorded. Plasma concentration of buprenorphine exceeded a presumed analgesic level (0.6 ng/ml) in five foals in the IV group and one in the SL group but only for a very brief time. Pharmacokinetic analysis following IV administration demonstrated a short elimination half-life (t_1/2β 1.95 ± 0.7 hr), large volume of distribution (6.46 ± 1.54 L/kg), and a high total clearance (55.83 ± 23.75 ml/kg/min), which differs from adult horses. Following SL administration, maximum concentrations reached were 0.61 ± 0.11 ng/ml and bioavailability was 25.1% ± 10.9%. In both groups, there were minor statistical differences in HR, RR, body temperature, locomotion, and time spent nursing. However, these differences were clinically insignificant in this single dose study, and excitement, sedation, or colic did not occur.

The Efficacy of Buprenorphine in Major Depression, Treatment-Resistant Depression and Suicidal Behavior: A Systematic Review

Although several pharmacological options to treat depression are currently available, approximately one third of patients who receive antidepressant medications do not respond adequately or achieve a complete remission. Thus, novel strategies are needed to successfully address those who did not respond, or partially respond, to available antidepressant pharmacotherapy. Research findings revealed that the opioid system is significantly involved in the regulation of mood and incentives salience and may be an appropriate target for novel therapeutic agents. The present study aimed to systematically review the current literature about the use of buprenorphine (BUP) for major depression, treatment-resistant depression (TRD), non-suicidal self-injury (NSSI) behavior, and suicidal behavior. We investigated Pubmed and Scopus databases using the following keywords: "buprenorphine AND depression", "buprenorphine AND treatment resistant depression", "buprenorphine AND suicid*", "buprenorphine AND refractory depression". Several evidence demonstrate that, at low doses, BUP is an efficacious, well-tolerated, and safe option in reducing depressive symptoms, serious suicidal ideation, and NSSI, even in patients with TRD. However, more studies are needed to evaluate the long-term effects, and relative efficacy of specific combinations (e.g., BUP + samidorphan (BUP/SAM), BUP + naloxone (BUP/NAL), BUP + naltrexone) over BUP monotherapy or adjunctive BUP treatment with standard antidepressants, as well as to obtain more uniform guidance about the optimal BUP dosing interval.

Treating Chronic Pain: An Overview of Clinical Studies Centered on the Buprenorphine Option

The buprenorphine receptor binding profile is unique in that it binds to all three major opioid receptors (mu, kappa, delta), and also binds to the orphan-like receptor, the receptor for orphanin FQ/nociceptin, with lower affinity. Within the mu receptor group, buprenorphine analgesia in rodents is dependent on the recently discovered arylepoxamide receptor target in brain, which involves a truncated 6-transmembrane mu receptor gene protein, distinguishing itself from morphine and most other mu opioids. Although originally designed as an analgesic, buprenorphine has mainly been used for opioid maintenance therapy and only now is increasingly recognized as an effective analgesic with an improved therapeutic index relative to certain potent opioids. Albeit a second-, third-, or fourth-line analgesic, buprenorphine is a reasonable choice in certain clinical situations. Transdermal patches and buccal film formulations are now commercially available as analgesics. This review discusses buprenorphine pharmacodynamics and pharmacokinetics, use in certain populations, and provides a synopsis of systematic reviews and randomized analgesic trials. We briefly discuss postoperative management in patients receiving buprenorphine maintenance therapy, opioid equivalence to buprenorphine, rotations to buprenorphine from other opioids, and clinical relevance of buprenorphine-related QTc interval changes.