Patterns of free (unconjugated) buprenorphine, norbuprenorphine, and their glucuronides in urine using liquid chromatography-tandem mass spectrometry

Patterns of buprenorphine and metabolites were examined in 1946 positive urine samples analyzed by liquid chromatography-tandem mass spectrometry for free (unconjugated) buprenorphine and norbuprenorphine (quantitative, 2 to 1000 ng/mL) and buprenorphine-glucuronide (B3G) and norbuprenorphine-glucuronide (N3G) (semi-quantitative, 5 to 1000 ng/mL). Two distribution patterns predominated with 49.1% positive for norbuprenorphine, B3G, and N3G and 41.6% positive for buprenorphine, norbuprenorphine, B3G, and N3G. Buprenorphine, positive in 45.5% of samples, was mostly < 5 ng/mL (median 6.1 ng/mL), but 9.8% were > 1000 ng/mL. Norbuprenorphine, B3G, and N3G had semi-Gaussian distributions with medians of 64.7, 108, and 432 ng/mL, respectively. With buprenorphine < 100 ng/mL (767 samples) or ≥ 100 ng/mL (19 quantifiable samples), the respective median metabolic ratios (free norbuprenorphine/free buprenorphine) were 25.0 and 0.15. In 12 retested "> 1000 ng/mL" buprenorphine samples, free buprenorphine was 4160 to 39,400 ng/mL and free naloxone 2140 to 9560 ng/mL. In 87 subsequent samples with buprenorphine < 20 ng/mL, naloxone concentrations were < 50 ng/mL. Concentrations of buprenorphine > 100 ng/mL (particularly with low metabolite concentrations) are suspect of urine adulteration with medication (4% in the database) that can be checked in most cases by concurrent analysis for naloxone.     

Quantitative testing of buprenorphine and norbuprenorphine to identify urine sample spiking during office-based opioid treatment

Background: Patients may spike urine samples with buprenorphine during office-based opioid treatment to simulate adherence to prescribed buprenorphine, potentially to conceal diversion of medications. However, routine immunoassay screens do not detect instances of spiking, as these would simply result in a positive result. The aim of this study was to report on the experience of using quantitative urine testing for buprenorphine and norbuprenorphine to facilitate the identification of urine spiking. Methods: This is a retrospective chart review of 168 consecutive patients enrolled in outpatient buprenorphine treatment at an urban academic medical setting between May 2013 and August 2014. All urine samples submitted were subjected to quantitative urine toxicology testing for buprenorphine and norbuprenorphine. Norbuprenorphine-to-buprenorphine ratio of less than 0.02 were further examined for possible spiking. Demographic and clinical variables were also extracted from medical records. Clinical and demographic variables of those who did and did not spike their urines were compared. Statistically significant variables from the univariate testing were entered as predictors of spiking in a regression analysis. Results: A total of 168 patients were included, submitting a total of 2275 urine samples. Patients provided on average 13.6 (SD = 9.9) samples, and were in treatment for an average 153.1 days (SD = 142.2). In total, 8 samples (0.35%) from 8 patients (4.8%) were deemed to be spiked. All of the samples suspected of spiking contained buprenorphine levels greater than 2000 ng/mL, with a mean norbuprenorphine level of 11.9 ng/mL. Spiked samples were submitted by 6 patients (75.0%) during the intensive outpatient (IOP) phase of treatment, 2 patients (25.0%) during the weekly phase, and none from the monthly phase. Regression analysis indicated that history of intravenous drug use and submission of cocaine-positive urine samples at baseline were significant predictors of urine spiking. Conclusions: Even though only a small number of patients were identified to have spiked their urine samples, quantitative testing may help identify urine spiking during office-based opioid treatment with buprenorphine.     

Analysis of buprenorphine, norbuprenorphine, and their glucuronides in urine by liquid chromatography-mass spectrometry

Buprenorphine is used for the treatment of chronic pain and also in treatment of heroin addiction as an alternative to methadone. As the availability of buprenorphine increases, so does the risk for abuse and the pressure on forensic and clinical laboratories to analyze for it. Buprenorphine and its dealkylated metabolite are excreted in urine, almost exclusively as glucuronides. The aim of the present study was to evaluate electrospray liquid chromatography tandem mass spectrometry (LC-MS-MS) for the rapid screening and quantitation of buprenorphine and its metabolites in urine. Three approaches were evaluated: (1) direct injection of diluted urine for measurement of glucuronides, (2) direct injection of diluted urine after enzymatic hydrolysis for the quantitation of buprenorphine and norbuprenorphine, and (3) quantitation of buprenorphine and norbuprenorphine after enzymatic hydrolysis and solid-phase extraction (SPE). One hundred six samples were subjected to procedure 1 and, when positive, further quantitated using procedure 2. Only samples with low analyte concentrations (< 20 microg/L) were subject to SPE. Concentrations of buprenorphine and norbuprenorphine in patients (N = 16) ranged between 31 and 1080 microg/L and 48-2050 microg/L, respectively. In suspected abusers (N = 33), the ranges were 2.3-796 microg/L and 5.0-2580 microg/L. In four of the authentic samples, both the buprenorphine and norbuprenorphine concentrations were below the 20- micro g/L cutoff. We concluded that LC-MS-MS analysis of the glucuronides provided an adequate screening method, but that the direct method for quantitation sometimes had to be complemented with a concentration by SPE, providing increased sensitivity, thus lowering the cutoff from 20 to 1 microg/L urine.     

Evaluation of buprenorphine CEDIA assay versus GC-MS and ELISA using urine samples from patients in substitution treatment

As buprenorphine becomes more clinically used in heroin substitution treatment, there is an increasing need for methods suitable for high-volume screening. In this study, a new immunochemical test based on CEDIA technology was evaluated for the use in clinical urine drug testing. The method was compared with an existing ELISA method and a gas chromatography-mass spectrometry (GC-MS) method on urine specimens from patients in heroin substitution treatment. The precision of the CEDIA assay was < 9% both within- and between-day at levels at and above the cutoff limit of 5 microg/L. The concordance in qualitative results with an existing ELISA method was 96.8%. The CEDIA measuring range was extended by diluting urine samples 100-fold with saline, and the results agreed well (slope of regression line was 1.09, r(2) = 0.968) with GC-MS. The sensitivity of CEDIA in detecting authentic specimen containing buprenorphine at levels >or= 5 microg/L was 99.5%. Cross-reactivity causing false-positive response was discovered in patients receiving prescribed dihydrocodeine. The urine concentration of total buprenorphine in urine from patients prescribed daily doses between 0.2 and 24 mg ranged from 0.5 to 2900 microg/L. The concentration of the metabolite norbuprenorphine was usually higher, and the median ratio of buprenorphine to norbuprenorphine was 0.23 (95% were below 1). We conclude that the CEDIA assay is suitable for application in high-volume screening of buprenorphine for urine drug testing.     

Urinary buprenorphine concentrations in patients treated with suboxone as determined by liquid chromatography-mass spectrometry and CEDIA immunoassay

We report on the utility of urine total buprenorphine, total norbuprenorphine, and creatinine concentrations in patients treated with Suboxone (a formulation containing buprenorphine and naloxone), used increasingly for the maintenance or detoxification of patients dependent on opiates such as heroin or oxycodone. Patients received 8-24 mg/day buprenorphine. Two-hundred sixteen urine samples from 70 patients were analyzed for both total buprenorphine and total norbuprenorphine by liquid chromatography-mass spectrometry (LC-MS-MS). Buprenorphine concentrations in all 176 samples judged to be unadulterated averaged 164 ng/mL, with a standard deviation (SD) of 198 ng/mL. Nine samples (4.2%) had metabolite-parent drug ratios < 0.02, and 33 (15.3%) had no detectable buprenorphine. The metabolite/parent drug ratio in 166 samples had a range of 0.07-23.0 (mean = 4.52; SD = 3.97). Fifteen of 96 available urine samples (16.7%) had creatinine less than 20 mg/dL. We also found sample adulteration in 7 (7.3%) available samples. Using a 5 ng/mL urine buprenorphine cutoff, the sensitivity and specificity of the Microgenics homogeneous enzyme immunoassay versus LC-MS-MS were 100% and 87.5%, respectively. The 5 ng/mL cutoff Microgenics CEDIA buprenorphine assay results agreed analytically with LC-MS-MS in 97.9% of samples.     

Determination of buprenorphine,norbuprenorphine, naloxone,and their glucuronides in urine by liquid chromatography–tandem mass spectrometry

A liquid chromatography–tandem mass spectrometry method for the simultaneous quantification of buprenorphine (BUP), norbuprenorphine (NBUP), naloxone (NAL), and their glucuronide conjugates BUP-G, NBUP-G, and NAL-G in urine samples was developed. The method, omitting a hydrolysis step, involved non-polar solid-phase extraction, liquid chromatography on a C18 column, electrospray positive ionization, and mass analysis by multiple reaction monitoring. Quantification was based on the corresponding deuterium-labelled internal standards for each of the six analytes. The limit of quantification was 0.5 μg/L for BUP and NAL, 1 μg/L for NAL-G, and 3 μg/L for NBUP, BUP-G, and NBUP-G. Using the developed method, 72 urine samples from buprenorphine-dependent patients were analysed to cover the concentration ranges encountered in a clinical setting. The median (maximum) concentration was 4.2 μg/L (102 μg/L) for BUP, 74.7 μg/L (580 μg/L) for NBUP, 0.9 μg/L (85.5 μg/L) for NAL, 159.5 μg/L (1370 μg/L) for BUP-G, 307.5 μg/L (1970 μg/L) for NBUP-G, and 79.6 μg/L (2310 μg/L) for NAL-G.     

Overdose Risk and Client Characteristics Associated With the Injection of Buprenorphine at a Medically Supervised Injecting Center in Sydney,Australia

Background: Buprenorphine and buprenorphine/naloxone (BNX) were developed to improve the safety profile of opioid substitution treatment (OST) and reduce diversion and injection, yet continue to be injected, despite the risk of harm. Previous studies examining injection of these substances have relied on self-reported injection and overdose. Using data from the Uniting Medically Supervised Injecting Center (MSIC) in Sydney, this study aimed to assess the overdose risk associated with the use of buprenorphine and BNX and identify factors associated with injecting. Methods: Client data routinely collected from MSIC, a drug consumption room where clients can legally inject drugs under supervision, was used. Odds ratios (OR) to assess the risk of overdose and their associated 95% confidence intervals (95%CI) were calculated and compared to other substances. Univariate analysis using χ-square and multivariate logistic regressions were used to determine characteristics associated with buprenorphine and BNX injection. Results: Data from 1,020,782 injections by 15,832 individuals were analyzed. Risk of overdose was low for buprenorphine compared to other substances (OR 0.16; 95%CI: 0.07–0.19) and no overdoses occurred when BNX was injected. Injection of both buprenorphine and BNX was associated with male gender, homelessness, no income/reliance upon government payments, and prior imprisonment. Conclusions: Buprenorphine and BNX continue to be injected, albeit in small numbers. This is the first study to report on injection and overdose risk using direct observation, and has confirmed the lower overdose risk. MSIC clients who inject buprenorphine and BNX tend to be marginalized and may benefit from targeted harm reduction measures.     

Using buprenorphine short-term taper to facilitate early treatment engagement

The U.S. Federal Food and Drug Administration approved buprenorphine for drug abuse treatment in 2002, and it became available for clinical use in early 2003. Maryhaven, a community treatment program, participated in a National Institute on Drug Abuse Clinical Trials Network trial evaluating buprenorphine–naloxone (BNX; Suboxone) short-term taper for medically managed opioid withdrawal and later adopted this treatment. In a retrospective review, the first 64 patients treated with a BNX taper were compared with two groups of patients treated with clonidine before and after the implementation of the BNX program. Significantly more patients (about 80%) receiving BNX continued in further treatment compared to about 30% of those receiving clonidine. Patient outcomes are discussed in the context of the critical need for treatment continuation following detoxification. Common questions of potential adopters of the BNX taper are presented and addressed. Overall, BNX was readily integrated into the existing treatment service.     

Quantitative analysis of buprenorphine and norbuprenorphine in urine using liquid chromatography tandem mass spectrometry

Buprenorphine is an opioid analgesic drug that is used as an alternative to methadone to treat heroin addiction. Established methods for the analysis of buprenorphine and its metabolites in urine such as gas chromatography-mass spectrometry (GC-MS) involve complicated sample extraction procedures. The aim of the present study was to develop a sensitive yet straightforward method for the simultaneous analysis of buprenorphine and norbuprenorphine in urine using liquid chromatography-MS-MS. The method comprised an enzymatic hydrolysis using Patella vulgata b-glucuronidase, followed by centrifugation and direct analysis of the supernatant. The limits of detection and quantitation were < 1 microg/L for buprenorphine and < 1 and 4 microg/L, respectively, for norbuprenorphine. Assay coefficients of variation (CVs) were < 15%, with the exception of concentrations close to the limit of quantitation, where CVs were below 20%. In direct comparison with an established GC-MS protocol, the method showed minimal negative bias (8.7% for buprenorphine and 1.8% for norbuprenorphine) and was less susceptible to sample carryover. The extent of conjugation in unhydrolyzed urine was investigated and found to be highly variable, with proportions of unconjugated buprenorphine and norbuprenorphine of 6.4% [range 0% to 67%; standard deviation (SD) 9.7%] and 34% (range 0% to 100%; SD 23.8%), respectively.     

Relative bioavailability of different buprenorphine formulations under chronic dosing conditions

BACKGROUND: Buprenorphine is an approved medication for the treatment of opioid dependence. Three sublingual formulations have been used at various times during its development-a solution containing alcohol, tablets containing buprenorphine alone, and tablets containing buprenorphine plus naloxone. This study compared the relative buprenorphine bioavailability of these different formulations. METHODS: Outpatient volunteers (N = 10) were maintained for 14 days of daily administration on each formulation; the dose of buprenorphine (8 mg) was constant across formulations. Blood samples were collected and tested for buprenorphine and norbuprenorphine concentrations after 7 and 14 days maintenance on each formulation. Serial samples were collected before and for 6 h after a daily dose of each formulation. RESULTS: Peak buprenorphine concentrations (C(max)) and area under the curve (AUC) for the 6h interval (AUC(0-6)) were highest for the solution and lowest for buprenorphine alone tablets; values for combination tablets were more similar to those for solution. Differences between formulations were less pronounced at day 14 than day 7. There was considerable between-subject variability in concentrations produced. CONCLUSIONS: These results suggest there may be greater bioavailability of buprenorphine/naloxone versus buprenorphine alone tablets, and that the bioavailability of buprenorphine from the former is very similar to that seen with solution after 2 weeks of stabilization on each formulation.     

Efficacy and safety of a sublingual buprenorphine/naloxone rapidly dissolving tablet for the treatment of adults with opioid dependence: A randomized trial

This prospective, randomized, active-controlled, non-inferiority study evaluated the efficacy and safety of a sublingual buprenorphine/naloxone rapidly dissolving tablet (Zubsolv^®; buprenorphine/naloxone rapidly dissolving tablet) versus generic buprenorphine for induction of opioid maintenance among dependent adults. The study, conducted at 13 sites from June 2013 to January 2014, included a 2-day blinded induction phase and a 27-day open-label stabilization/maintenance phase. During the blinded induction, patients received fixed doses of buprenorphine/naloxone rapidly dissolving tablets or generic buprenorphine. During open-label stabilization/early maintenance, all patients received buprenorphine/naloxone rapidly dissolving tablets. The primary efficacy assessment was treatment retention at day 3; buprenorphine/naloxone rapidly dissolving tablets were considered non-inferior to generic buprenorphine if the lower limit of the 95% confidence interval for the difference between the treatments was ≥–10% in patients retained on day 3. Secondary assessments included opioid withdrawal symptoms and cravings as measured using the Clinical Opiate Withdrawal Scale, the Subjective Opiate Withdrawal Scale, and the opioid cravings visual analogue scale. Safety was also assessed. A total of 313 patients were randomly assigned to induction with generic buprenorphine or buprenorphine/naloxone rapidly dissolving tablets. The mean age was 38.4 years, and the mean duration of opioid dependence was 12.4 years. For the primary efficacy assessment, 235 of 256 patients (91.8%) were retained at day 3 and continued to the maintenance phase. The lower limit of the 95% confidence interval was ?13.7; thus, buprenorphine/naloxone rapidly dissolving tablets did not demonstrate non-inferiority to generic buprenorphine, and significantly more patients who received induction with generic buprenorphine (122/128 [95.3%]) were retained at day 3 compared with those who received induction with buprenorphine/naloxone rapidly dissolving tablets (113/128 [88.3%]; 95% confidence interval: ?13.7, ?0.4; p = 0.040). The rates of clinical response, as measured by the Clinical Opiate Withdrawal Scale, the Subjective Opiate Withdrawal Scale, and the visual analogue scale, were comparable among patients regardless of the induction medication. Treatment with buprenorphine/naloxone rapidly dissolving tablets was generally safe and reduced the severity of withdrawal symptoms and cravings.     

High‐dose buprenorphine for treatment of high potency opioid use disorder

A 29‐year‐old woman presented to detox for treatment of an opioid use disorder with illicit fentanyl. While in detox, she was started on opioid agonist treatment with buprenorphine/naloxone. Unfortunately, she continued to have withdrawal symptoms despite being optimised to a dose of 32 mg. She was given additional PRNs of buprenorphine/naloxone to a total daily dose of 40 mg, which helped to alleviate her symptoms of withdrawal and cravings. She was stabilised on buprenorphine/naloxone 40 mg daily without any side effects and was discharged to a rehabilitation centre.     

Determination of buprenorphine and norbuprenorphine in urine and hair by gas chromatography-mass spectrometry.

Buprenorphine, which is used in France as a substitution drug for opioid addiction, is widely abused, and several fatal cases have been reported. In order to confirm a recent intoxication or to establish retrospectively chronic abuse, a simple and reliable gas chromatographic-mass spectrometric method was developed and validated for quantitation of buprenorphine and its active metabolite norbuprenorphine in urine and hair. Two milliliters of urine or 50 mg of pulverized hair was submitted to a pretreatment (enzymatic hydrolysis for urine and decontamination with dichloromethane followed by incubation in 0.1 M HCI for hair). Buprenorphine-d4 was chosen as the internal standard. Selective solid-phase extraction with Bond Elut Certify columns provided recoveries higher than 85% for urine and 43% for hair. By using a mixture of MSTFA/TMSIM/TMCS (100:2:5), buprenorphine and norbuprenorphine produced stable silylated derivatives. The detection was carried out with a quadrupole mass detector working in El selected ion monitoring mode. Ions at m/z 450 and 468 were chosen for the quantitation of buprenorphine and norbuprenorphine, respectively (m/z 454 was used for the internal standard). Limits of quantitation were 0.25 and 0.20 ng/mL, respectively, for buprenorphine and norbuprenorphine in urine and 0.005 ng/mg for the two compounds in hair. Calibration curves were linear from 0 to 50 ng/mL in urine and from 0 to 0.4 ng/mg in hair. Between-day and within-day precisions were less than 8.4% in hair and 6.1% in urine for both molecules in all cases. This method was applied to urine and hair samples collected from patients in a withdrawal treatment program and demonstrated its good applicability in routine analysis and its benefit for clinicians. This technique, which requires instruments already available to many toxicology laboratories, offers an attractive alternative to more sophisticated techniques.     

Blockade of hydromorphone effects by buprenorphine/naloxone and buprenorphine

RATIONALE: Buprenorphine is an opioid agonist-antagonist used in the treatment of opioid dependence. Naloxone has been combined with buprenorphine to decrease the parenteral abuse potential of buprenorphine. This addition of naloxone may also confer further opioid blockade efficacy. OBJECTIVES: To test the opioid blockade efficacy of sublingual buprenorphine/naloxone versus buprenorphine alone and determine whether: (1) the blockade efficacy of buprenorphine/naloxone varies between the time of expected maximal and minimal effects of naloxone, (2) the blockade efficacy of buprenorphine/naloxone and buprenorphine varies as a function of maintenance dose level, and (3) there are adaptive changes over time associated with repeated daily dosing of buprenorphine/naloxone and buprenorphine. METHODS: Residential subjects ( n=6) were maintained on different double-blind dose levels of buprenorphine/naloxone (4/1, 8/2, 16/4, 32/8 mg) and buprenorphine (32 mg) for 6-day periods and challenged with parenteral doses of hydromorphone (12 mg) in laboratory sessions. RESULTS: There was no evidence of additional opioid blockade efficacy conferred by combining naloxone with buprenorphine. Higher doses of buprenorphine/naloxone provided greater blockade of hydromorphone effects. Changes over time associated with repeated daily dosing of buprenorphine/naloxone and buprenorphine were minimal. CONCLUSIONS: The addition of naloxone to buprenorphine may deter the parenteral abuse of buprenorphine/naloxone, but it does not enhance the therapeutic efficacy of buprenorphine. The blockade efficacy of buprenorphine/naloxone is dose related; however, doses up to 32/8 mg buprenorphine/naloxone provide only partial blockade when subjects receive a high dose of an opioid agonist.     

Effect of buprenorphine dose on treatment outcome

The goal of this meta-analysis is to provide evidence based information about proper dosing for buprenorphine maintenance treatment to improve treatment outcome. To be selected for the review and inclusion in the meta-analysis, articles had to be randomized, controlled, or double-blind clinical trials, with buprenorphine as the study drug; the length of buprenorphine maintenance treatment had to be 3 weeks or longer; doses of buprenorphine had to be clearly stated; outcome measures had to include retention rates in buprenorphine treatment; outcome measures had to include illicit opioid use based on analytical determination of drugs of abuse in urine samples as outcome variables; and outcome measures had to include illicit cocaine use based on analytical determination of drugs of abuse in urine samples as outcome variables. Twenty-nine articles were excluded because they did not meet the inclusion criteria. The authors present the results of 21 articles that met inclusion criteria. The higher buprenorphine dose (16-32 mg per day) predicted better retention in treatment compared with the lower dose (less than 16 mg per day) (P = .009, R(2) adjusted = 0.40), and the positive urine drug screens for opiates predicted dropping out of treatment (P = .019, R(2) Adjusted = 0.40). Retention in treatment predicted less illicit opioid use (P = .033, R(2) Adjusted = 0.36), and the positive urine drug screens for cocaine predicted more illicit opioid use (P = .021, R(2) Adjusted = 0.36). Strong evidence exists based on 21 randomized clinical trials that the higher buprenorphine dose may improve retention in buprenorphine maintenance treatment.     

Validation of the Immunalysis microplate ELISA for the detection of buprenorphine and its metabolite norbuprenorphine in urine

The purpose of this study was to validate the Immunalysis Buprenorphine Microplate enzyme-linked immunosorbent assay (ELISA) for the detection of buprenorphine in urine samples. Sixty-nine urine samples were obtained from volunteers on the Subutex treatment program and from routine samples submitted to the laboratory for buprenorphine testing. For ELISA analysis, samples were diluted 1:10 with K(2)HPO(4) (0.1M, pH 7.0). The limit of detection was calculated as 0.5 ng/mL buprenorphine. The intra-assay and interday precision was 3.8% (n = 10) and 8.6% (n = 50) respectively at 1 ng/mL buprenorphine. At a low concentration of norbuprenorphine (1 ng/mL), the immunoassay demonstrated a cross-reactivity of 78%. A higher cross-reactivity of 116% was observed at a higher concentration of norbuprenorphine (10 ng/mL). Dihydrocodeine, codeine, tramadol, morphine, propoxyphene, methadone, and EDDP were tested at concentrations of 10 ng/mL and 10,000 ng/mL and demonstrated no cross-reactivity with the assay. For liquid chromatography-tandem mass spectrometry (LC-MS-MS), deuterated internal standard mixture, 1M acetate buffer (pH 5.0), and b-glucuronidase were added to the standards and samples, which were then incubated for 3 h at 60 degrees C. After incubation, 3 mL K(2)HPO(4) (0.1M, pH 6.0) was added and the pH altered to pH 6.0 using 1M KOH. Buprenorphine and norbuprenorphine were subsequently extracted by solid-phase. Twenty-one samples were confirmed positive and 48 samples were confirmed negative by LC-MS-MS. Using a cut-off value of 0.5 ng/mL buprenorphine, the immunoassay demonstrated a sensitivity and specificity of 100%.     

Effects of buprenorphine versus buprenorphine/naloxone tablets in non-dependent opioid abusers

Rationale: Buprenorphine is an opioid agonist-antagonist under development in the United States as a sublingual medication for treatment of opioid dependence. Buprenorphine may be abused; therefore, tablets combining buprenorphine with naloxone have been developed with the intent of reducing the abuse risk in people physically dependent upon opioids. The characteristics and abuse potential of buprenorphine and buprenorphine/naloxone tablets in non-dependent opioid abusers have not been determined. Non-parenteral abuse of opioids such as buprenorphine may be more likely in people who have less severe substance abuse disorders (e.g., are not physically dependent upon opioids). Objectives: To assess the abuse potential of sublingual buprenorphine and buprenorphine/naloxone tablets in non-dependent opioid abusers. Methods: Subjects (n=7) were tested with sublingual buprenorphine (4, 8, 16 mg), sublingual buprenorphine/naloxone (1/0.25, 2/0.5, 4/1, 8/2, 16/4 mg), as well as intramuscular hydromorphone as an opioid agonist control (2, 4 mg) and placebo in laboratory sessions conducted twice per week. Dosing was double-blind and double-dummy. Results: The higher doses of both buprenorphine and buprenorphine/naloxone produced similar opioid agonist-like effects. The onset of these effects was slowed, consistent with the sublingual route of administration, and the magnitude of effects was moderate. There was no evidence to suggest the addition of naloxone attenuated buprenorphine’s opioid agonist effects in this population when buprenorphine was delivered by the sublingual route. Conclusions: These results suggest that sublingual buprenorphine and buprenorphine/naloxone may both be abused by opioid users who are not physically dependent upon opioids. Received: 15 April 1999 / Final version: 11 September 1999     

Buprenorphine: clinical pharmacokinetics in the treatment of opioid dependence

Buprenorphine is a semi-synthetic opioid derived from thebaine, a naturally occurring alkaloid of the opium poppy, Papaver somniferum. The pharmacology of buprenorphine is unique in that it is a partial agonist at the opioid mu receptor. Buprenorphine undergoes extensive first-pass metabolism and therefore has very low oral bioavailability; however, its bioavailability sublingually is extensive enough to make this a feasible route of administration for the treatment of opioid dependence. The mean time to maximum plasma concentration following sublingual administration is variable, ranging from 40 minutes to 3.5 hours. Buprenorphine has a large volume of distribution and is highly protein bound (96%). It is extensively metabolised by N-dealkylation to norbuprenorphine primarily through cytochrome P450 (CYP) 3A4. The terminal elimination half-life of buprenorphine is long and there is considerable variation in reported values (mean values ranging from 3 to 44 hours). Most of a dose of buprenorphine is eliminated in the faeces, with approximately 10-30% excreted in urine. Naloxone has been added to a sublingual formulation of buprenorphine to reduce the abuse liability of the product. The presence of naloxone does not appear to influence the pharmacokinetics of buprenorphine. Buprenorphine crosses the placenta during pregnancy and also crosses into breast milk. Buprenorphine dosage does not need to be significantly adjusted in patients with renal impairment; however, since CYP3A activity may be decreased in patients with severe chronic liver disease, it is possible that the metabolism of buprenorphine will be altered in these patients. Although there is limited evidence in the literature to date, drugs that are known to inhibit or induce CYP3A4 have the potential to diminish or enhance buprenorphine N-dealkylation. It appears that the interaction between buprenorphine and benzodiazepines is more likely to be a pharmacodynamic (additive or synergistic) than a pharmacokinetic interaction. The relationship between buprenorphine plasma concentration and response in the treatment of opioid dependence has not been well studied.The pharmacokinetic and pharmacodynamic properties of buprenorphine allow it to be a feasible option for substitution therapy in the treatment of opioid dependence.     

The in vivo glucuronidation of buprenorphine and norbuprenorphine determined by liquid chromatography-electrospray ionization-tandem mass spectrometry

The opioid partial agonist medication, buprenorphine (BUP), and its primary metabolite, norbuprenorphine (NBUP), are extensively glucuronidated. Sensitive analytical methods that include determination of buprenorphine-3-glucuronide (BUPG) and norbuprenorphine-3-glucuronide (NBUPG) are needed to more fully understand the metabolism and pharmacokinetics of buprenorphine. A method has now been developed that uses solid-phase extraction followed by liquid chromatography-electrospray ionization-tandem mass spectrometry. BUP-d4, NBUP-d3, and morphine-3-glucuronide-d3 were used as internal standards. The lower limit of quantitation was 0.1 and 0.5 ng/mL for each of the analytes in 1-mL of human plasma and urine, respectively, except for NBUP in urine in which it was 2.5 ng/mL. The analytes were stable under the following conditions: plasma and urine at room temperature, up to 20 hours; plasma and urine at -20 degrees C for 119 and 85 days, respectively; plasma freeze-thaw, up to 3 cycles; processed sample, up to 96 hours at -20 degrees C and up to 48 hours on the autosampler; stock solutions at room temperature and at -20 degrees C, up to 6 hours and 128 days, respectively. In plasma collected from 5 subjects on maintenance daily sublingual doses of 16 mg BUP and 4 mg naloxone, respective 0- to 24-hour areas under the curve were 32, 88, 26, and 316 ng/mL x h for BUP, NBUP, BUPG, and NBUPG. In urine samples respective percent of daily dose excreted in the 24-hour urine were 0.014%, 1.89%, 1.01%, and 7.76%. This method allowed us to determine that NBUPG is a major metabolite present in plasma and urine of BUP. Because urinary elimination is limited ( approximately 11% of daily dose), the role of NBUPG in total clearance of buprenorphine is not yet known.     

阿片类药物替代疗法:安全性和滥用倾向的比较研究

阿片类药物维持疗法是治疗阿片、海洛因和阿片类制剂依赖的有效方法。美沙酮和丁丙诺啡是世界范围内最常用于替代治疗的阿片类药物,纳曲酮作为一种阿片受体的拮抗剂用于阻断治疗。研究数据显示维持疗法比脱毒疗法疗效更好,但是,存在长期用药剂量的安全性问题,包括对药物的直接反应和滥用风险。对美沙酮和丁丙诺啡(单独使用或与纳曲酮合用)的研究揭示了剂量与效应的关系,以及最佳的用药方案。研究数据提示,在呼吸抑制(过量)和对心血管的直接作用方面丁丙诺啡较美沙酮风险更低。丁丙诺啡,作为一种部分激动剂,可能比美沙酮或者海洛因等完全激动剂的滥用倾向更小。本文提供的数据说明在阿片依赖的个体上丁丙诺啡的滥用风险较美沙酮的更低。最近的数据提示,在阿片依赖和非依赖的使用者中,丁丙诺啡/纳曲酮合用的滥用潜力低于丁丙诺啡单独使用。