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

Development and Verification of a Full Physiologically Based Pharmacokinetic Model for Sublingual Buprenorphine in Healthy Adult Volunteers that Accounts for Nonlinear Bioavailability

Sublingual buprenorphine is used for opioid use disorder and neonatal opioid withdrawal syndrome. The study aimed to develop a full physiologically based pharmacokinetic (PBPK) model that can adequately describe dose- and formulation-dependent bioavailability of buprenorphine. Simcyp (v21.0) was used for model construction. Four linear regression models (i.e., untransformed or log transformed for dose or proportion sublingually absorbed) were explored to describe sublingual absorption of buprenorphine across dose. Published clinical trial data not used in model development were used for verification. The PBPK model's predictive performance was deemed adequate if the geometric means of ratios between predicted and observed (P/O) area under the curve (AUC), peak concentration (Cmax), and time to reach Cmax (Tmax) fell within the 1.25-fold prediction error range. Sublingual buprenorphine absorption was best described by a regression model with logarithmically transformed dose. By integrating this nonlinear absorption profile, the PBPK model adequately predicted buprenorphine pharmacokinetics (PK) following administration of sublingual tablets and solution across a dose range of 2-32 mg, with geometric mean (95% confidence interval) P/O ratios for AUC and Cmax equaling 0.99 (0.86-1.12) and 1.24 (1.09-1.40), respectively, and median (5th to 95th percentile) for Tmax equaling 1.11 (0.69-1.57). A verified PBPK model was developed that adequately predicts dose- and formulation-dependent buprenorphine PK following sublingual administration. SIGNIFICANCE STATEMENT: The physiologically based pharmacokinetic (PBPK) model developed in this study is the first to adequately predict dose- and formulation-dependent sublingual buprenorphine pharmacokinetics. Accurate prediction was facilitated by the incorporation of a novel nonlinear absorption model. The developed model will serve as the foundation for maternal-fetal PBPK modeling to predict maternal and fetal buprenorphine exposures to optimize buprenorphine treatment for neonatal opioid withdrawal syndrome.

Current and Future Therapeutic Options in Pain Management: Multi-mechanistic Opioids Involving Both MOR and NOP Receptor Activation

Opioids are widely used in chronic pain management, despite major concerns about their risk of adverse events, particularly abuse, misuse, and respiratory depression from overdose. Multi-mechanistic opioids, such as tapentadol and buprenorphine, have been widely studied as a valid alternative to traditional opioids for their safer profile. Special interest was focused on the role of the nociceptin opioid peptide (NOP) receptor in terms of analgesia and improved tolerability. Nociceptin opioid peptide receptor agonists were shown to reinforce the antinociceptive effect of mu opioid receptor (MOR) agonists and modulate some of their adverse effects. Therefore, multi-mechanistic opioids involving both MOR and NOP receptor activation became a major field of pharmaceutical and clinical investigations. Buprenorphine was re-discovered in a new perspective, as an atypical analgesic and as a substitution therapy for opioid use disorders; and buprenorphine derivatives have been tested in animal models of nociceptive and neuropathic pain. Similarly, cebranopadol, a full MOR/NOP receptor agonist, has been clinically evaluated for its potent analgesic efficacy and better tolerability profile, compared with traditional opioids. This review overviews pharmacological mechanisms of the NOP receptor system, including its role in pain management and in the development of opioid tolerance. Clinical data on buprenorphine suggest its role as a safer alternative to traditional opioids, particularly in patients with non-cancer pain; while data on cebranopadol still require phase III study results to approve its introduction on the market. Other bifunctional MOR/NOP receptor ligands, such as BU08028, BU10038, and AT-121, are currently under pharmacological investigations and could represent promising analgesic agents for the future.

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.

Buprenorphine for Chronic Pain: A Safer Alternative to Traditional Opioids

With the ongoing public health crisis with prescription opioids, there is a need for safer alternatives for medication management in chronic pain patients. Buprenorphine is a partial mu-opioid agonist which is commonly utilized to treat patients with opioid-use disorders. The purpose of this review is to discuss the potential use of this medication for the treatment of chronic pain instead of resorting to more traditional Schedule II opioids. Buprenorphine offers a safer alternative for patients who require opioids to manage chronic pain, given the unique pharmacological properties that allow it to provide adequate analgesia with less abuse potential.

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.

The utilization of buprenorphine in chronic pain

Reclassification of chronic pain as a disease may be helpful because patients with chronic pain require significant treatment and rehabilitation with a clear diagnosis. This can help address critical factors including suffering, quality of life, participation, and with family and social life, which continue to become more important in evaluating the quality of the health care we give our patients today. During the past decade of the opioid epidemic, methadone was the primary treatment for opioid addiction until buprenorphine was approved. Buprenorphine's high-affinity partial agonist properties make it a good alternative to methadone due to lower abuse potential and safer adverse effect profile while maintaining significant efficacy. Expanded out-patient prescribing options have allowed physician and physician extenders such as physician assistants and nurse practitioners to treat these patients that otherwise would have been required to utilize methadone. With unique pharmacological properties, buprenorphine is a safe and effective analgesic for chronic pain. The literature for buprenorphine shows great potential for its utilization in the treatment of chronic pain.

Pharmacokinetics of low-dose and high-dose buprenorphine in cats after rectal administration of different formulations

OBJECTIVES

A prospective experimental study was performed in nine young healthy cats to investigate a pharmacokinetic profile and the clinical relevance of rectally administered buprenorphine. Rectal pH value was measured in all nine cats.

METHODS

Blood was collected 15, 30, 60, 90, 120, 240 and 480 mins and 24 h after the rectal administration of a suppository and a gel at doses between 0.02 mg/kg and 0.1 mg/kg buprenorphine to determine the plasma concentration of buprenorphine. Rectal pH was measured with pH paper.

RESULTS

Upon pharmacokinetic non-compartment analysis of high-dose buprenorphine (0.1 mg/kg), average maximal plasma concentration was found to be 1.13 ng/ml, time to maximal plasma concentration was 45 mins and area under the plasma concentration-time curve was 94.19 ng*min/ml, representing low but potential bioavailability. Mean residual time was 152.2 mins and the half-life was 92.6 mins. A wide range of plasma concentrations within the cohort was measured and two of the cats had to be excluded from statistical analysis owing to incomplete uptake. Vital parameters of all cats were considered to be normal but three of the cats showed mydriasis up to 8 h after application. After the administration of a low-dose suppository or a rectal gel (0.02 mg/kg) within pilot studies, no buprenorphine was detected in cat plasma. Rectal pH in all cats was between 7.7 and 8.

CONCLUSIONS AND RELEVANCE

The rectal application of buprenorphine at a dose of 0.1 mg/kg revealed a potential but weak uptake in cats. Regarding effective concentrations in previous pharmacokinetic investigations, rectal administration is currently not recommended for good provision of opioid analgesia in cats. Pharmacological investigations of formulation and galenics in order to improve the rectal bioavailability of buprenorphine remain to be clarified before further dose-finding and pharmacokinetic/pharmacodynamic studies are performed.