Pharmacokinetics, bioavailability and opioid effects of liquid versus tablet buprenorphine

Population Pharmacokinetic Analysis Supports Initiation Treatment and Bridging from Sublingual Buprenorphine to Subcutaneous Administration of a Buprenorphine Depot (CAM2038) in the Treatment of Opioid Use Disorder

BACKGROUND AND OBJECTIVE

In treating opioid use disorder (OUD), subcutaneous (SC) extended-release buprenorphine (BPN) depots, e.g., CAM2038, have been shown to provide smaller and less frequent fluctuations in BPN plasma concentrations and pharmacodynamic responses, improve outcomes, reduce treatment burden, and lower risks of misuse and diversion compared to daily sublingual (SL) BPN. This analysis characterized the pharmacokinetics (PK) of BPN following intravenous and SL administration, and administration of SC CAM2038 weekly and monthly.

METHODS

Pharmacokinetic data from two Phase 1 and two Phase 2 trials in healthy participants and participants with OUD, respectively, were used to develop a population PK model using non-linear mixed effects modelling. The analysis included data from 252 participants and 10,658 BPN observations.

RESULTS

The disposition of BPN was best described by a three-compartment model with first-order elimination, and absorption of SL BPN and SC CAM2038 weekly and monthly by dual parallel absorption pathways. Model diagnostics indicated good predictive performance of BPN concentrations. Buprenorphine plasma concentration-time profiles were simulated for treatment initiation, switching from SL BPN to CAM2038 weekly and monthly, and tapering after interrupting treatment with CAM2038. Simulations predicted CAM2038 weekly and monthly doses that provided BPN plasma maximum concentration (Cmax) and trough concentration (Ctrough) values at steady state within those observed following SL BPN administration.

CONCLUSIONS

This population PK model supports the use of CAM2038 doses as individualized treatment for OUD across different treatment stages, including initiation, switching from SL BPN according to established dose conversion schedules, and tapering.

TRIAL REGISTRATIONS

ISRCTN41550730 (05/19/2014), ISRCTN24987553 (07/29/2014), NCT02611752 (11/23/2015), NCT02710526 (03/16/2016).

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.

Classics in Chemical Neuroscience: Buprenorphine

Buprenorphine has not only had an interdisciplinary impact on our understanding of key neuroscience topics like opioid pharmacology, pain signaling, and reward processing but has also been a key influence in changing the way that substance use disorders are approached in modern medical systems. From its leading role in expanding outpatient treatment of opioid use disorders to its continued influence on research into next-generation analgesics, buprenorphine has been a continuous player in the ever-evolving societal perception of opioids and substance use disorder. To provide a multifaceted account on the enormous diversity of areas where this molecule has made an impact, this article discusses buprenorphine's chemical properties, synthesis and development, pharmacology, adverse effects, manufacturing information, and historical place in the field of chemical neuroscience.

Opioid prescription patterns for pediatric orthopaedic fracture patients

BACKGROUND

While hospitalizations attributed to opioid poisonings are increasing in the pediatric population, the patterns of prescribing behaviors of health care providers remains unclear. The aims of this study were to identify the opioid prescribing patterns of an orthopaedic team for post-surgical pediatric orthopaedic fracture patients, and to examine whether patient demographics, injury type, and type of providers were associated with the opioid prescribing patterns at discharge.

METHODS

A retrospective chart review was performed among all patients aged 0-18 years undergoing surgery for elbow, forearm, wrist, femur, tibia and ankle fractures between 2014 and 2016 at a large children's hospital. Inclusion criteria were patients with isolated operative fractures involving the elbow, forearm, wrist, femur, tibia or ankle who received an opioid prescription at discharge prescribed by a member of the orthopaedic team. Exclusion criteria included patients discharged without opioids or patients discharged with opioid prescriptions from another medical team.

RESPONSE

1000 unique patients (546 male) were identified, with average age of 7.9 years. The most common fracture was elbow (67.2%), followed by femur (12.4%), ankle (9.4%), forearm (5.8%), wrist (4.6%), and tibia (1.6%). Average dose of opioids prescribed was 28.4 (SD = 11.5) per patient. All prescriptions followed recommended guidelines for each medication. Patients who were older (p < 0.0001) or heavier (p < 0.0001) were prescribed a significantly greater average number of opioid doses. Nurse practitioners wrote 57.0% of the discharge prescriptions, followed by residents (23.0%) and physician assistants (14.5%). Attending surgeons accounted for only 5.5% of prescriptions. Residents and physician assistants prescribed significantly higher average doses than nurse practitioners and attending surgeons (p < 0.0001). Patients receiving liquid opioids received a statistically significant (p < 0.001) smaller number of doses than patients receiving tablets.

CONCLUSIONS

Pediatric orthopaedic trauma patients appear to be receiving generic numbers of opioid pain medication doses after fracture surgery due to universal rather than injury-specific prescribing patterns. Further study is required to determine the appropriate number of doses per injury type.

A physiologically based pharmacokinetic modelling approach to predict buprenorphine pharmacokinetics following intravenous and sublingual administration

AIMS

Opioid dependence is associated with high morbidity and mortality. Buprenorphine (BUP) is approved by the Food and Drug Administration to treat opioid dependence. There is a lack of clear consensus on the appropriate dosing of BUP due to interpatient physiological differences in absorption/disposition, subjective response assessment and other patient comorbidities. The objective of the present study was to build and validate robust physiologically based pharmacokinetic (PBPK) models for intravenous (IV) and sublingual (SL) BUP as a first step to optimizing BUP pharmacotherapy.

METHODS

BUP-PBPK modelling and simulations were performed using SimCyp® by incorporating the physiochemical properties of BUP, establishing intersystem extrapolation factors-based in vitro-in-vivo extrapolation (IVIVE) methods to extrapolate in vitro enzyme activity data, and using tissue-specific plasma partition coefficient estimations. Published data on IV and SL-BUP in opioid-dependent and non-opioid-dependent patients were used to build the models. Fourteen model-naïve BUP-PK datasets were used for inter- and intrastudy validations.

RESULTS

The IV and SL-BUP-PBPK models developed were robust in predicting the multicompartment disposition of BUP over a dosing range of 0.3-32 mg. Predicted plasma concentration-time profiles in virtual patients were consistent with reported data across five single-dose IV, five single-dose SL and four multiple dose SL studies. All PK parameter predictions were within 75-137% of the corresponding observed data. The model developed predicted the brain exposure of BUP to be about four times higher than that of BUP in plasma.

CONCLUSION

The validated PBPK models will be used in future studies to predict BUP plasma and brain concentrations based on the varying demographic, physiological and pathological characteristics of patients.

Probuphine® (buprenorphine implant): a promising candidate in opioid dependence

Opioid dependence leads to physical dependence and addiction which finally results in profound medical, psychological and social dysfunction. One of the useful medications for opioid dependence is buprenorphine, the partial opioid agonist, which is used alone or in combination with naloxone. However, buprenorphine is the victim of its own success due to its illicit use and accidental poisoning in children. Also, buprenorphine typically requires daily self-administration and its effectiveness heavily depends on patient adherence. So, poor treatment adherence results in ineffective treatment manifesting as craving and withdrawal symptoms. Short-term use of buprenorphine in opioid dependence is also often followed by relapse. Buprenorphine when used sublingually often results in inadequate or fluctuating blood concentrations and poorer treatment retention compared with methadone. All of these led to the development of Probuphine®, a polymeric matrix composed of ethylene vinyl acetate and buprenorphine in the form of implants, that are implanted subdermally in office practice and deliver the active drug over 6 months. Buprenorphine release from such implant is fairly consistent, avoiding plasma peaks and troughs, and the implant is also reported to be safe. In this review article, we have highlighted these aspects of treatment of opioid addiction, stressing on the pharmacology of buprenorphine and Probuphine®, and relevant clinical trials addressing the efficacy and safety of Probuphine®. This sustained-release implantable formulation of buprenorphine has the potential to be a suitable alternative to daily or alternate day sublingual buprenorphine which can thereby eliminate the need for daily supervision, minimizing fluctuations in plasma concentrations, and allowing these patients to reduce clinic or pharmacy visits.

Effects of a higher-bioavailability buprenorphine/naloxone sublingual tablet versus buprenorphine/naloxone film for the treatment of opioid dependence during induction and stabilization: a multicenter, randomized trial

PURPOSE

Sublingual buprenorphine and combination buprenorphine/naloxone (BNX) are effective options for the treatment of opioid dependence. A BNX sublingual tablet approved by the US Food and Drug Administration for the induction and maintenance treatment of opioid-dependence in adults was developed as a higher-bioavailability formulation, allowing for a 30% lesser dose of buprenorphine with bioequivalent systemic exposure compared with another BNX sublingual tablet formulation. No data were previously available comparing the higher-bioavailability BNX sublingual tablet to generic buprenorphine or BNX sublingual film; we therefore evaluated treatment retention during induction and stabilization with the higher-bioavailability BNX sublingual tablet versus generic buprenorphine or BNX sublingual film.

METHODS

This multicenter, prospective, randomized, parallel-group noninferiority trial was conducted at 43 centers in the United States. Eligible patients were adults aged 18 to 65 years who met the criteria for opioid dependence and had at least mild withdrawal symptoms. On days 1 and 2, patients received blinded, fixed-dose induction with the higher-bioavailability BNX sublingual tablet or generic buprenorphine. On days 3 to 14, patients induced with BNX received open-label, titrated doses of the BNX tablet for stabilization; patients induced with buprenorphine received sublingual BNX film. Co-primary end points were treatment retention on days 3 and 15; noninferiority was concluded if the lower limit of the 95% CI of the between-group difference in treatment retention was ≥-10%. Tolerability was assessed throughout the study period.

FINDINGS

A total of 758 opioid-dependent patients were included in the study (BNX sublingual tablet, 383 patients; generic buprenorphine, 375). Day-3 retention rates were 93.9% (309/329) and 92.6% (302/326) with the BNX tablet and buprenorphine, respectively (between-group difference 95% CI, -2.6 to 5.1). Day-15 retention rates were 83.0% (273/329) and 82.5% (269/326) with the BNX tablet and BNX film, respectively (between-group difference 95% CI, -5.3 to 6.3). No unexpected tolerability issues were identified; the safety profile of the BNX sublingual tablet was similar to those of generic buprenorphine and BNX film.

IMPLICATIONS

Based on the findings from this study in patients with opioid dependence, the higher-bioavailability BNX sublingual tablet formulation was noninferior to both generic buprenorphine (induction) and BNX film (stabilization). These findings suggest that BNX sublingual tablets are an efficacious and well-tolerated option for induction and early stabilization treatment of opioid dependence. ClinicalTrials.gov identifier: NCT01908842.

The introduction of buprenorphine-naloxone film in opioid substitution therapy in Australia: Uptake and issues arising from changing buprenorphine formulations

INTRODUCTION AND AIMS

Buprenorphine-naloxone (BNX) film for opioid dependence treatment was introduced in Australia in 2011. A key difference in State policy approaches saw transfer from BNX tablets to BNX film mandated in South Australia (SA) with New South Wales (NSW) and Victoria (VIC) having less stringent policies. This study examined (i) how initiations and transfers were implemented, (ii) the profile and predictors of adverse effects as self-reported by BNX film clients, and (iii) dosing issues.

DESIGN AND METHODS

Survey of 334 buprenorphine (BPN), BNX tablet and BNX film clients and semi-structured interviews with 39 key experts (KEs) in 2012. Comparisons are made between clients interviewed in SA versus NSW and VIC combined.

RESULTS

Among the 180 current BNX film clients, 23% started treatment on BNX film, 18% requested a transfer to BNX film and 59% (n = 106) reported their clinic/prescriber recommended transfer to BNX film. Among clients who were offered but refused a transfer to BNX film (n = 66), the most common reason was 'I am happy with my current treatment and do not see a reason to change' (53%). Some opioid substitution therapy clients and KE viewed transfers as 'forced' (i.e. no choice of buprenorphine formulation). Multivariable regression showed residing in SA (vs. NSW/VIC) and a shorter length of current treatment episode were associated with more BNX film-attributed adverse effects but clinic/prescriber-recommended transfer was not.

DISCUSSION AND CONCLUSIONS

The introduction of BNX film in Australia varied across States. A perception of restricted choice in medication may have undermined initial acceptance in SA.

Buprenorphine maintenance and mu-opioid receptor availability in the treatment of opioid use disorder: implications for clinical use and policy

BACKGROUND

Sublingual formulations of buprenorphine (BUP) and BUP/naloxone have well-established pharmacokinetic and pharmacodynamic profiles, and are safe and effective for treating opioid use disorder. Since approvals of these formulations, their clinical use has increased. Yet, questions have arisen as to how BUP binding to mu-opioid receptors (μORs), the neurobiological target for this medication, relate to its clinical application. BUP produces dose- and time-related alterations of μOR availability but some clinicians express concern about whether doses higher than those needed to prevent opioid withdrawal symptoms are warranted, and policymakers consider limiting reimbursement for certain BUP dosing regimens.

METHODS

We review scientific data concerning BUP-induced changes in μOR availability and their relationship to clinical efficacy.

RESULTS

Withdrawal suppression appears to require ≤50% μOR availability, associated with BUP trough plasma concentrations ≥1 ng/mL; for most patients, this may require single daily BUP doses of 4 mg to defend against trough levels, or lower divided doses. Blockade of the reinforcing and subjective effects of typical doses of abused opioids require <20% μOR availability, associated with BUP trough plasma concentrations ≥3 ng/mL; for most individuals, this may require single daily BUP doses >16 mg, or lower divided doses. For individuals attempting to surmount this blockade with higher-than-usual doses of abused opioids, even larger BUP doses and <10% μOR availability would be required.

CONCLUSION

For these reasons, and given the complexities of studies on this issue and comorbid problems, we conclude that fixed, arbitrary limits on BUP doses in clinical care or limits on reimbursement for this care are unwarranted.

Buprenorphine implant for opioid addiction

SUMMARY The buprenorphine implant (Probuphine™, Titan Pharmaceuticals, CA, USA) is a recently developed long-acting formulation of buprenorphine, which is a partial opioid agonist that is widely used in the marketed, sublingual, daily-dose form for managing opioid addiction. The new formulation uses a novel delivery system consisting of subcutaneously implanted solid matrix 'rods' made from a mixture of ethylene vinyl acetate and buprenorphine. The buprenorphine implant was developed to ensure medication compliance, eliminate misuse and abuse from diversion of sublingual buprenorphine, and increase therapeutic benefit of the medication. The implant is not a 'new' drug, but an innovative means of delivering a medication proven effective for treating opioid addiction. The implant has not yet been approved by the US FDA. The information in this review has been gleaned from research reports, documentation in the literature, and from the author's experience treating opioid-dependent patients, and involvement in clinical research examining sublingual buprenorphine and the buprenorphine implant.

Medication-assisted treatment for opioid addiction: methadone and buprenorphine

Among agents for treatment of opioid addiction, methadone is a full mu-opioid receptor agonist, whereas buprenorphine is a partial agonist. Both are long-acting. Buprenorphine has a superior safety profile. Methadone is formulated for oral administration and buprenorphine for sublingual administration. A subdermal buprenorphine implant with a 6-month duration of action is being considered for approval by the U.S. Food and Drug Administration. Both medications reduce mortality rates and improve other outcomes. Data from a recent randomized controlled comparison of both medications (N = 1269) show better treatment retention with methadone but reduced illicit opioid use early in treatment with buprenorphine. Human immunodeficiency virus (HIV) risk behaviors were measured using the Risk Behavior Survey at baseline, 12 weeks, and 24 weeks for study completers. In the 30 days prior to treatment entry, 14.4% of the completers randomized to treatment with buprenorphine (n = 340) and 14.1% of the completers randomized to methadone treatment (n = 391) shared needles. The percent sharing needles decreased to 2.4% for buprenorphine and 4.8 for methadone in the 30 days prior to Week 24 (p < 0.0001). In the 30 days prior to treatment entry, 6.8% of the completers randomized to buprenorphine and 8.2% of the completers randomized to methadone had multiple sexual partners, with only 5.2% and 5.1%, respectively, reporting multiple partners at Week 24 (p < 0.04).

A double blind, within subject comparison of spontaneous opioid withdrawal from buprenorphine versus morphine

Preliminary evidence suggests that there is minimal withdrawal after the cessation of chronically administered buprenorphine and that opioid withdrawal symptoms are delayed compared with those of other opioids. The present study compared the time course and magnitude of buprenorphine withdrawal with a prototypical μ-opioid agonist, morphine. Healthy, out-of-treatment opioid-dependent residential volunteers (N = 7) were stabilized on either buprenorphine (32 mg/day i.m.) or morphine (120 mg/day i.m.) administered in four divided doses for 9 days. They then underwent an 18-day period of spontaneous withdrawal, during which four double-blind i.m. placebo injections were administered daily. Stabilization and spontaneous withdrawal were assessed for the second opioid using the same time course. Opioid withdrawal measures were collected eight times daily. Morphine withdrawal symptoms were significantly (P < 0.05) greater than those of buprenorphine withdrawal as measured by mean peak ratings of Clinical Opiate Withdrawal Scale (COWS), Subjective Opiate Withdrawal Scale (SOWS), all subscales of the Profile of Mood States (POMS), sick and pain (0-100) Visual Analog Scales, systolic and diastolic blood pressure, heart rate, respiratory rate, and pupil dilation. Peak ratings on COWS and SOWS occurred on day 2 of morphine withdrawal and were significantly greater than on day 2 of buprenorphine withdrawal. Subjective reports of morphine withdrawal resolved on average by day 7. There was minimal evidence of buprenorphine withdrawal on any measure. In conclusion, spontaneous withdrawal from high-dose buprenorphine appears subjectively and objectively milder compared with that of morphine for at least 18 days after drug cessation.

Retention in methadone and buprenorphine treatment among African Americans

Methadone has been the most commonly used pharmacotherapy for the treatment of opioid dependence in U.S. public sector treatment, but availability of buprenorphine as an alternative medication continues to increase. Drawing data from two community-based clinical trials that were conducted nearly contemporaneously, this study examined retention in methadone versus buprenorphine treatment over 6 months among urban African Americans receiving treatment in one of four publicly-funded programs (N=478; 178 methadone; 300 buprenorphine). Adjusting for confounds related to medication selection, survival analysis revealed that buprenorphine patients are at substantially higher risk of dropout compared to methadone patients (HR=2.43; p<.001). Buprenorphine's retention disadvantage appears to be concentrated in the earlier phases of treatment (approximately the first 50 days), after which risk of subsequent dropout becomes similar for the two medications. These findings confirm a retention disparity between methadone and buprenorphine in this population, and suggest potential avenues for future research to enhance retention in buprenorphine treatment.

Pharmacokinetics of buprenorphine: a comparison of sublingual tablet versus liquid after chronic dosing

Although buprenorphine is approved for use in the outpatient treatment of opioid addiction in 2 tablet formulations, a monoproduct containing buprenorphine only (Subutex) and a buprenorphine/naloxone combination product (Suboxone), much of the clinical data that support the approval by the U.S. Food and Drug Administration were generated by using a sublingual liquid. To interpret the literature in prescribing parameters for tablet buprenorphine, this study was designed to determine steady state buprenorphine plasma levels for the 2 formulations and to assess the relative bioavailability of each. A randomized, double-blind, crossover study with dose increases was conducted during a 12-week period at an outpatient treatment clinic. Of the 184 subjects initially randomized to treatment, 133 (72.3%) were evaluated for the steady-state trough plasma concentration, 16 (8.7%) for relative bioavailability, and 31 (16.8%) for dose proportionality. At steady state, differences in the trough plasma concentrations of buprenorphine between the 2 formulations were found across all the dose levels. Average plasma concentration (Cavg) of the tablet at twice the milligram dose of the liquid was twice that of the liquid; intersubject variability was greater for the tablet. At double the dose of tablet, there is no difference in steady state plasma concentrations. The bioavailability seems equivalent for the 2 formulations across all the dose levels.

Buprenorphine-mediated transition from opioid agonist to antagonist treatment: state of the art and new perspectives

Constant refinement of opioid dependence (OD) therapies is a condition to promote treatment access and delivery. Among other applications, the partial opioid agonist buprenorphine has been studied to improve evidence-based interventions for the transfer of patients from opioid agonist to antagonist medications. This paper summarizes PubMed-searched clinical investigations and conference papers on the transition from methadone maintenance to buprenorphine and from buprenorphine to naltrexone, discussing challenges and advances. The majority of the 26 studies we examined were uncontrolled investigations. Many small clinical trials have demonstrated the feasibility of in- or outpatient transfer to buprenorphine from low to moderate methadone doses (up to 60-70 mg). Results on the conversion from higher methadone doses, on the other hand, indicate significant withdrawal discomfort, and need for ancillary medications and inpatient treatment. Tapering high methadone doses before the transfer to buprenorphine is not without discomfort and the risk of relapse. The transition buprenorphine-naltrexone has been explored in several pilot studies, and a number of treatment methods to reduce withdrawal intensity warrant further investigation, including the co-administration of buprenorphine and naltrexone. Outpatient transfer protocols using buprenorphine, and direct comparisons with other modalities of transitioning from opioid agonist to antagonist medications are limited. Given its potential salience, the information gathered should be used in larger clinical trials on short and long-term outcomes of opioid agonist-antagonist transition treatments. Future studies should also test new pharmacological mechanisms to help reduce physical dependence, and identify individualized approaches, including the use of pharmacogenetics and long-acting opioid agonist and antagonist formulations.

Pharmacokinetics, pharmacodynamics, and comparative bioavailability of single, oral 2-mg doses of dexamethasone liquid and tablet formulations: a randomized, controlled, crossover study in healthy adult volunteers

BACKGROUND

Dexamethasone is a glucocorticoid used widely worldwide for immunosuppressive treatment, allergies, bronchiolitis, and croup, among others. For children, liquid formulations are especially suitable because, compared with other dosage forms, both exact dosing and proper intake are facilitated.

OBJECTIVE

The objective was to evaluate the pharmacokinetics, pharmacodynamics, and comparative bioavailability of a commercial liquid oral dexamethasone formulation intended for pediatric use relative to those of a tablet.

METHODS

In a randomized, controlled, crossover study in 24 healthy adult volunteers, we administered single doses of the liquid and tablet formulation, containing 2 mg of dexamethasone each. Blood samples were taken up to 24 hours postdose. Quantification was carried out using a validated specific and sensitive high-pressure liquid chromatography with UV detector method. Noncompartmental pharmacokinetic parameters were compared between treatments according to European Medicines Agency (EMA) bioequivalence guidelines. For AUC(0-t) and C(max), the 90% CI for the ratio of the test and reference products should be contained within the predetermined acceptance interval of 80% to 125%. As a pharmacodynamic variable, we measured suppression of endogenous cortisol (predose and postdose).

RESULTS

Both preparations showed similar pharmacokinetic and pharmacodynamic profiles but high between-subject variability of pharmacokinetic key parameters and endogenous cortisol concentrations (>30%). Mean AUC(0-t), AUC(0-∞), and C(max) were 37.8 ng/mL/h, 46.0 ng/mL/h, and 9.35 ng/mL, respectively, for the liquid and 41.3 ng/mL/h, 48.1 ng/mL/h, and 9.17 ng/mL, respectively, for the tablet formulation. T(max) was 0.89 hour (liquid) and 0.97 hour (tablet). The point estimates and 90% CIs for AUC(0-t), AUC(0-∞), and C(max) ratios (liquid vs tablet) were 91.42% (82.05%-101.86%), 95.72% (84.46%-108.5%), and 102.04% (86.94%-119.76%), respectively. Thus, point estimates and 90% CIs were within the bioequivalence range of 80% to 125% for all relevant parameters, including the pharmacodynamic parameter AUEC (area under the effect curve).

CONCLUSIONS

This single-dose study suggests that the test and reference products met the EMA regulatory criteria to assume bioequivalence in these fasting healthy male and female volunteers. German Register of Clinical Trials registration number: DRKS00000785.

Health-related quality of life changes associated with buprenorphine treatment for opioid dependence

BACKGROUND

Few studies have described improvement in health-related quality of life (HRQOL) associated with opioid dependence treatment with buprenorphine (ODT-B).

OBJECTIVE

To evaluate HRQOL changes in domain scores, physical and mental component summaries, and health utilities (HUs) associated with ODT-B using the Short Form 36 (SF-36).

METHODS

We assessed HRQOL changes in a substudy of a pharmacokinetic study that compared buprenorphine oral tablet and liquid dosage formulations over 16 weeks. Individuals, aged 18-65 years, were screened for opioid dependence. They were excluded if they would not agree to birth control or had a serious medical condition. Subjects received psychosocial counseling and weekly group therapy. The SF-36 was administered upon enrollment and at 4-week intervals. We used the SF-6D to estimate HUs. We performed intention to treat (ITT) analyses based on the last observation available for each subject. Paired t tests of each domain and HU, limited to remaining patients at each 4-week interval, were also conducted.

RESULTS

Of 96 subjects enrolled, cumulative dropouts over time resulted in 80, 69, 59, and 44 subjects remaining at 4, 8, 12, and 16 weeks. There were no significant differences in opioid-positive urines, dropout rates, or dosage changes between formulations. In the ITT analyses, HRQOL improvements over time were bodily pain (62.1 vs. 69.1, P = 0.017), vitality (49.8 vs. 56.5, P = 0.001), mental health (59.9 vs. 66.0, P = 0.001), social function (66.4 vs. 74.7, P = 0.001), role emotional (59.4 vs. 71.9, P = 0.003), role physical (60.9 vs. 70.6, P = 0.005), and mental component summary (41.9 vs. 45.4, P<0.001). HU scores also improved (0.674 vs. 0.715, P = 0.001). Results from paired t tests, with only concurrently enrolled patients, showed similar improvements from baseline to 4, 8, 12, or 16 weeks.

CONCLUSION

Buprenorphine, accompanied with psychosocial counseling, was associated with improved HRQOL and HUs.

Preliminary buprenorphine sublingual tablet pharmacokinetic data in plasma, oral fluid, and sweat during treatment of opioid-dependent pregnant women

BACKGROUND

Buprenorphine is currently under investigation as a pharmacotherapy to treat pregnant women for opioid dependence. This research evaluates buprenorphine (BUP), norbuprenophine (NBUP), buprenorphine-glucuronide (BUP-Gluc), and norbuprenorphine-glucuronide (NBUP-Gluc) pharmacokinetics after high-dose (14-20 mg) BUP sublingual tablet administration in three opioid-dependent pregnant women.

METHODS

Oral fluid and sweat specimens were collected in addition to plasma specimens for 24 hours during gestation weeks 28 or 29 and 34, and 2 months after delivery. Time to maximum concentration was not affected by pregnancy; however, BUP and NBUP maximum concentration and area under the curve at 0 to 24 hours tended to be lower during pregnancy compared with postpartum levels.

RESULTS

Statistically significant but weak positive correlations were found for BUP plasma and OF concentrations and BUP/NBUP ratios in plasma and oral fluid. Statistically significant negative correlations were observed for times of specimen collection and BUP and NBUP oral fluid/plasma ratios. BUP-Gluc and NBUP-Gluc were detected in only 5% of oral fluid specimens. In sweat, BUP and NBUP were detected in only four of 25 (12 or 24 hours) specimens in low concentrations (less than 2.4 ng/patch).

CONCLUSION

These preliminary data describe BUP and metabolite pharmacokinetics in pregnant women and suggest that, like methadone, upward dose adjustments may be needed with advancing gestation.

The World Federation of Societies of Biological Psychiatry (WFSBP) guidelines for the biological treatment of substance use and related disorders. Part 2: Opioid dependence

OBJECTIVES

To develop evidence-based practice guidelines for the pharmacological treatment of opioid abuse and dependence.

METHODS

An international task force of the World Federation of Societies of Biological Psychiatry (WFSBP) developed these practice guidelines after a systematic review of the available evidence pertaining to the treatment of opioid dependence. On the basis of the evidence, the Task Force reached a consensus on practice recommendations, which are intended to be clinically and scientifically meaningful for physicians who treat adults with opioid dependence. The data used to develop these guidelines were extracted primarily from national treatment guidelines for opioid use disorders, as well as from meta-analyses, reviews, and publications of randomized clinical trials on the efficacy of pharmacological and other biological treatments for these disorders. Publications were identified by searching the MEDLINE database and the Cochrane Library. The literature was evaluated with respect to the strength of evidence for efficacy, which was categorized into one of six levels (A-F).

RESULTS

There is an excellent evidence base supporting the efficacy of methadone and buprenorphine or the combination of buprenorphine and naloxone for the treatment of opioid withdrawal, with clonidine and lofexidine as secondary or adjunctive medications. Opioid maintenance with methadone and buprenorphine is the best-studied and most effective treatment for opioid dependence, with heroin and naltrexone as second-line medications.

CONCLUSIONS

There is enough high quality data to formulate evidence-based guidelines for the treatment of opioid abuse and dependence. This task force report provides evidence for the efficacy of a number of medications to treat opioid abuse and dependence, particularly the opioid agonists methadone or buprenorphine. These medications have great relevance for clinical practice.

Energy-dependent collision-induced dissociation study of buprenorphine and its synthetic precursors

The collision-induced dissociation (CID) of protonated buprenorphine ([M+H](+) ) and four related compounds was studied by electrospray quadrupole/time-of-flight mass spectrometry (ESI-QTOF MS). The fragmentation pathways were investigated by using energy-dependent CID and pseudo-MS(3) (in-source CID combined with tandem mass spectrometry (MS/MS)) methods. The first steps of the fragmentation are the parallel losses of the substituents from the non-aromatic ring moieties. Depending on the applied collision energies, a large number of further fragment ions arising from the cross-ring cleavages of the core-ring structure were observed. Based on the experimental results, a generalized fragmentation scheme was developed for the five buprenorphine derivatives highlighting the differences for the alternatively substituted compounds. The collision-energy-dependent fragmentation profile of buprenorphine is visualized in a two-dimensional plot to aid its fingerprint identification.

Buprenorphine for opioid dependence

As a treatment agent for opioid dependence, buprenorphine is a nearly ideal medication at our current stage of medication development. Unlike methadone, buprenorphine dosage can be rapidly adjusted with minimal potential for inducing severe consequences. In addition to its intrinsic safety, buprenorphine's relatively low abuse liability in the combination product (i.e., with naloxone as Suboxone) makes it even more acceptable in regulatory quarters as well as to prescribing physicians. The approval of buprenorphine as a pharmacotherapy for opioid dependence returns to physicians the ability to treat their opioid-dependent patients with an effective opioid-based treatment for the first time in nearly 100 years. Buprenorphine is an opioid, however, and potential for misuse remains, even in combination with naloxone. Whether buprenorphine will be increasingly accepted as a treatment for opioid-dependent patients depends on clinicians recognizing the advantages of its uniquely useful properties while still heeding the need to manage their patients' therapy with reasonable vigilance.

The impact of community pharmacy dispensing fees on the introduction of buprenorphine-naloxone in Australia

INTRODUCTION AND AIMS

The introduction of buprenorphine - naloxone in Australia in April 2006 has permitted the revision of takeaway policies in many states and has introduced the possibility of unsupervised treatment. This study explored the implications of the introduction of buprenorphine - naloxone in terms of cost to patients through a survey of pharmacists' intended pricing practices. The aim of the research was to examine the intentions of pharmacists in relation to fees for buprenorphine - naloxone and study the potential implications to patients when compared with the existing fee structure for methadone and for buprenorphine alone.

DESIGN AND METHODS

A self-complete questionnaire was mailed to every community pharmacy in New South Wales (NSW) (n = 593) dispensing methadone or buprenorphine to people with opioid dependence. A response rate of 68.6% (n = 407) was achieved after three mailouts.

RESULTS

The majority of pharmacies charged a flat weekly fee for methadone (92.2%; mean = $31.90) and buprenorphine (74.8%; mean = $31.00). The mean intended fees for buprenorphine - naloxone according to different dosing and takeaway regimens ranged from $19.19 per week for no supervised doses and fortnightly takeaways to a $30.88 per week flat fee. There appeared to be little variation in fee structure irrespective of the takeaway regimen, until reaching the 2 weeks' unsupervised dose regimen.

DISCUSSION AND CONCLUSIONS

This study highlights the importance of the early dissemination of unambiguous information regarding the introduction of a new medication, especially where supervised dispensing through community pharmacies is essential to the provision of treatment. The potential impact upon the successful rollout of a new treatment paradigm that was developed to benefit stable patients in the community may be jeopardised when such processes are not followed.

The effects of maternally administered methadone, buprenorphine and naltrexone on offspring: review of human and animal data

Most women using heroin are of reproductive age with major risks for their infants. We review clinical and experimental data on fetal, neonatal and postnatal complications associated with methadone, the current "gold standard", and compare these with more recent, but limited, data on developmental effects of buprenorphine, and naltrexone. Methadone is a micro-opioid receptor agonist and is commonly recommended for treatment of opioid dependence during pregnancy. However, it has undesired outcomes including neonatal abstinence syndrome (NAS). Animal studies also indicate detrimental effects on growth, behaviour, neuroanatomy and biochemistry, and increased perinatal mortality. Buprenorphine is a partial micro-opioid receptor agonist and a kappa-opioid receptor antagonist. Clinical observations suggest that buprenorphine during pregnancy is similar to methadone on developmental measures but is potentially superior in reducing the incidence and prognosis of NAS. However, small animal studies demonstrate that low doses of buprenorphine during pregnancy and lactation lead to changes in offspring behaviour, neuroanatomy and biochemistry. Naltrexone is a non-selective opioid receptor antagonist. Although data are limited, humans treated with oral or sustained-release implantable naltrexone suggest outcomes potentially superior to those with methadone or buprenorphine. However, animal studies using oral or injectable naltrexone have shown developmental changes following exposure during pregnancy and lactation, raising concerns about its use in humans. Animal studies using chronic exposure, equivalent to clinical depot formulations, are required to evaluate safety. While each treatment is likely to have maternal advantages and disadvantages, studies are urgently required to determine which is optimal for offspring in the short and long term.

Endogenous opiates and behavior: 2006

This paper is the 29th consecutive installment of the annual review of research concerning the endogenous opioid system, now spanning 30 years of research. It summarizes papers published during 2006 that studied the behavioral effects of molecular, pharmacological and genetic manipulation of opioid peptides, opioid receptors, opioid agonists and opioid antagonists. The particular topics that continue to be covered include the molecular-biochemical effects and neurochemical localization studies of endogenous opioids and their receptors related to behavior (Section 2), and the roles of these opioid peptides and receptors in pain and analgesia (Section 3); stress and social status (Section 4); tolerance and dependence (Section 5); learning and memory (Section 6); eating and drinking (Section 7); alcohol and drugs of abuse (Section 8); sexual activity and hormones, pregnancy, development and endocrinology (Section 9); mental illness and mood (Section 10); seizures and neurological disorders (Section 11); electrical-related activity and neurophysiology (Section 12); general activity and locomotion (Section 13); gastrointestinal, renal and hepatic functions (Section 14); cardiovascular responses (Section 15); respiration and thermoregulation (Section 16); and immunological responses (Section 17).

Functionalization of the 6,14-bridge of the orvinols. Part 3: preparation and pharmacological evaluation of 18- and 19-hydroxyl substituted orvinols

The orvinols are a class of potent opioids which have been extensively studied, yet little is known about the effects of introducing substituents into the 18- and 19-positions. The etheno bridge of thevinone was hydroxylated to give both the 18- and 19-hydroxyl substituted thevinols. After 3-O-demethylation to the corresponding orvinols, binding and GTPgammaS functional assays indicated that hydroxyl substitution at the 18- and 19-positions differentially affects the mu opioid efficacy of orvinols.

Buprenorphine-containing treatments: place in the management of opioid addiction

Although the synthetic opioid buprenorphine has been available clinically for almost 30 years, its use has only recently become much more widespread for the treatment of opioid addiction. The pharmacodynamic and pharmacokinetic profiles of buprenorphine make it unique in the armamentarium of drugs for the treatment of opioid addiction. Buprenorphine has partial mu-opioid receptor agonist activity and is a kappa-opioid receptor antagonist; hence, it can substitute for other micro-opioid receptor agonists, yet is less apt to produce overdose reactions or dysphoria. On the other hand, buprenorphine can block the effects of opioids such as heroin (diamorphine) and morphine, and can even precipitate withdrawal in individuals physically dependent upon these drugs. Buprenorphine has significant sublingual bioavailability and a long half-life, making administration on a less than daily basis possible. Furthermore, its discontinuation is associated with only a mild withdrawal syndrome. Clinical trials have demonstrated that sublingual buprenorphine is effective in both maintenance therapy and detoxification of individuals addicted to opioids. The introduction of a sublingual formulation combining naloxone with buprenorphine further reduces the risk of diversion to illicit intravenous use. Because of its relative safety and lower risk of illegal diversion, buprenorphine has been made available in several countries for treating opioid addiction in the private office setting, greatly enhancing treatment options for this condition.