Buprenorphine and Naloxone Combination for Opioid Dependence

Transcription

1 DELHI PSYCHIATRY JOURNAL Vol. 13 No.1 APRIL 2010 Drug Review Buprenorphine and Naloxone Combination for Opioid Dependence M.S. Bhatia*, S. Srivastava*, G. Rajender*, S. Malhotra**, D. Chaudhary*** *Department of Psychiatry GT.B. Hospital & UCMS Delhi, University of Delhi **Institute of Human Behaviour and Allied Sciences, Dilshad Garden, Delhi ***S.M.S. Medical College, Jaipur Introduction Buprenorphine/ naloxone comprises the partial µ-opioid receptor agonist buprenorphine in combination with the opioid antagonist naloxone in a 4:1 ratio. Psychosocial therapy and pharmacotherapy are the two main modalities for the treatment of opioid dependence. 1 Medically supervised withdrawal (detoxification) uses an opioid agonist and/or other anti-withdrawal agent (e.g. clonidine) to address the physical dependence component of illicit opioid abuse 2 and facilitate entry into drug-free therapy or transition to treatment with an opioid antagonist, such as naltrexone. Maintenance treatment uses a long-acting opioid agonist to reduce opioid craving while preventing opioid withdrawal. Maintenance therapy with the long-acting opioid agonist methadone has long been considered the treatment of choice for chronic opioid dependence.but various concerns have been raised with methadone use as: 1. Full opioid agonists may experience physical withdrawal when a daily dose is missed Ther apeutic discontinuation can be discouragingly difficult and lengthy. 3. No ceiling to respiratory depression and or sedation effects 4. Fear of potential abuse, misuse and diversion and associated concomitant morbidity and mortality. Buprenorphine, a partial µ-opioid receptor agonist, has pharmacodynamic advantages over methadone and may be used as an alternative treatment for opioid dependence. It may be potentially safer in overdose situations and have an easier withdrawal phase. 4 In contrast to methadone and levacetylmethadol (levomethadyl acetate), buprenorphine can now legally be administered in an office-based setting in India, like in the US 1 where it had expanded access to treatment for opioid dependence. 5 The combined bupr enorphine/naloxone for mulation was developed to reduce this problem of illicit diversion of buprenorphine. 2,6 This article reviews the pharmacological properties and evidence for clinical use of buprenorphine/naloxone formulation. Pharmacodynamic properties Buprenorphine acts as a partial µ-opioid receptor agonist and an antagonist at the k-opioid receptor. The high binding affinity of buprenorphine for the m-opioid receptor and its slow dissociation results in long duration of action. Naloxone is an opioid antagonist without agonist properties. The different dose ratios of 2 : 1, 4 :1 or 8: 1 buprenorphine/naloxone have been investigated and only the 2 : 1 and 4 : 1 ratios were found to significantly increased all measures of opioid withdrawal relative to buprenorphine alone 7. The acute sublingual administration at equivalent dose levels of buprenorphine, the physiological and subjective effects of buprenorphine/ naloxone and buprenorphine have been reported to be similar 8.All buprenorphine/ naloxone doses as 4mg/ 1 mg, 8mg/ 2 mg, 16 mg/4mg and 32 mg/8mg have been found to produce a partial but stable blockade of agonist effects for at least 25 hours 9.Evidence suggests that the dose of sublingual buprenorphine/naloxone optimal for reducing the agonist effects of heroin may be above 2mg/0.5 mg and below 32 mg/8 mg 10. The effects of buprenorphine in the buprenorphine/ naloxone combination are long-acting, effects last for up to 98 hours, supporting a potential for less than daily dosing 11. In non-opioid dependent 164

2 APRIL 2010 DELHI PSYCHIATRY JOURNAL Vol. 13 No.1 individuals, the addition of naloxone to buprenorphine may attenuate the opioid agonist effects of buprenorphine 12. It may precipitate withdrawal in full agonist opioid dependent patients if it is administered before the agonist effects of full opioid agonists have worn of. 8 But the administration of split doses may attenuate the subjective experience of withdrawal 13. The increasing doses of buprenorphine/naloxone (from 8mg/ 2mg through to 32 mg/ 8 mg) does not result in escalating impairment of most measures of psychomotor and cognitive performance. 14 Pharmacokinetic Properties Absorption and Distribution Complete dissolution of sublingual buprenorphine/naloxone tablets was reported to occur 4, 7 and 8 minutes following administration of 4mg/1mg (two tablets), 8mg/2mg (one tablet) and 16mg/4mg (two tablets), respectively 15. Peak plasma concentrations of buprenorphine are achieved 90 minutes after sublingual administration 16. The mean bioavailability of buprenorphine sublingual solution is 28 51%.The plasma bioavailability of sublingual buprenorphine tablets has been estimated at 49 63% of that of the sublingual solution 17, 8mg solution of buprenorphine roughly equivalent to 12mg tablet and 16mg solution roughly equivalent to 24 mg tablet) 8. Studies suggest that the addition of naloxone does not affect the pharmacokinetics of buprenorphine 8,17. Evidence also suggests that plasma concentrations of buprenorphine are time and dose related. No significant differences in plasma buprenorphine concentrations between the oncedaily group 24 hours after receipt of an 8mg dose and the thrice-weekly group 72 hours after receipt of a 24mg dose 18. Distribution of buprenorphine is rapid (distribution half-life is 2 5 hours) 16. Buprenorphine is highly bound to protein (96%), primarily to á and â globulin. Naloxone is 45% protein bound, mostly to albumin 8. Buprenorphine is metabolized by N-dealkylation and glucuronidation. Cytochrome P450 (CYP) 3A4 mediates N-dealkylation of buprenorphine to norbuprenorphine, a µ-opioid agonist with only weak intrinsic activity at this site. The mean elimination half-life from plasma is 37 hours for buprenorphine and 1.1 hours for naloxone 16,8. Drug Interactions Inhibitors of CYP3A4 (such as azole antifungals, macrolide, antibacterials and HIV protease inhibitors) may increase plasma concentrations of bupr enorphine, and patients concomitantly receiving these medications should be closely monitored and may require buprenorphine/ naloxone dosage reductions. 8 Clinical trials and evidence of clinical efficacy In the treatment of opioid dependence, buprenorphine alone has well established efficacy as a maintenance therapy 19,20 and as a medically supervised withdrawal treatment 21,22. When taken sublingually as prescribed, the opioid agonist and antagonist effects of buprenorphine/naloxone have been shown to be largely indistinguishable from those of buprenorphine alone. This section focuses on only those trials of the buprenorphine/naloxone sublingual tablet which have used a 4 : 1 buprenorphine : naloxone ratio. Sublingual buprenorphine/naloxone therapy has been reported to be an effective maintenance therapy for opioid dependence. 23 The percentage of illicit opioid-negative urine samples was significantly (p < 0.001) higher among buprenorphine/naloxone recipients than placebo recipients. Also the mean opioid craving score during each week was significantly lower in the buprenorphine/ naloxone group than in the placebo group. Overall status scores through weeks 1 4, denoting the improvement from baseline in overall health and well-being, were significantly (all p < 0.001) higher at each week with buprenorphine/ naloxone or buprenorphine alone versus placebo as rated by the patient or clinician, thus indicating greater improvement. 23 In a seventeen week trial comparing with methadone 45 or 90 mg/day, the percentage of opioid-negative urine samples did not significantly differ between patients receiving buprenorphine/ naloxone 8mg/ 2mg or 16mg/4mg per day and those receiving methadone 45 or 90 mg/day. Also there were no significant differences between the buprenorphine/naloxone 8mg/2 mg, buprenorphine/ naloxone 16mg/4 mg, methadone 45 mg and methadone 90 mg groups in the percentage of 165

3 DELHI PSYCHIATRY JOURNAL Vol. 13 No.1 APRIL 2010 patients with e 12 consecutive opioid-negative urine samples 24. In terms of 6-month retention rates in the stepped care trial, starting patients on bupr enorphine/naloxone with transition to methadone if necessary was non inferior to methadone alone (odds ratio of 1.02) 25. Several trials examined the efficacy of buprenorphine/naloxone maintenance therapy with different counselling and/or medication-dispensing regimens 26,27. In these trials, buprenorphine/ naloxone was not significantly less effective at reducing illicit opioid use (as assessed by surrogate and/or self-reported measures) when medication was dispensed or administered at less frequent intervals. No significant differences in efficacy across groups receiving different levels of counselling (standard vs enhanced medical management) or observed versus unobserved dosing were noted. However, patients preferred dosing schedules in which they were less frequently required to attend a clinic or office for medication dispensing or administration. In real world settings two studies reported outcomes associated with buprenorphine/naloxone maintenance treatment in real world primary care settings 28,29. Both studies examined the use of induction, stabilization and maintenance treatment with buprenorphine/ naloxone in opioid-dependent patients (n = 99 and 41). One study involved two primary-care centers and had a primary endpoint of sobriety at 6 months 28. The other study, a retrospective chart review, involved one primarycare centre. Maintenance treatment with buprenorphine/naloxone was effective in real world primary care settings. At 6 months, 53 of 99 (54%) patients were sober in one study. At day 90 in the other study, 29 of 41 (71%) patients were retained in treatment 29. Opioid detoxification Methadone, buprenorphine alone, á-adrenergic agonist clonidine and buprenorphine/naloxone have been used as medically-supervised withdrawal agents 1. A Cochrane review of trials of buprenorphine alone for the management of opioid withdrawal showed buprenorphine to be more effective than clonidine and of similar efficacy to methadone 30. In two prospective, randomized studies, buprenorphine/naloxone was also found to be more effective than clonidine as a medicallysupervised withdrawal therapy 31,32. Buprenorphine/ naloxone treated inpatients and outpatients were significantly more likely to complete the study and provide an illicit-opioid-free urine sample at study completion than patients treated with clonidine in the same treatment settings. In fact, buprenorphine/ naloxone recipients were 9-fold more likely than clonidine recipients to achieve treatment success (OR 9.50, p < 0.001) 33. In addition, inpatients were more likely than outpatients to achieve treatment success (OR 7.27; p < 0.001); the relationship between medication type and retention in treatment was moderated by the treatment setting. Moreover, patients with higher versus lower early withdrawal scores on the Clinical Opiate Withdrawal Scale (COWS) were more likely to achieve treatment success (OR 4.40; p = 0.004); the reduction from baseline to day 3 in opioid withdrawal severity scores was a moderating factor in treatment outcomes. Treatment success did not seem to be influenced by sociodemographic factors such as age, gender, ethnicity, employment status and years of education 33. No data are currently available comparing the efficacy of buprenorphine/naloxone with methadone for medically-supervised withdrawal therapy. Tapering Schedules Studies report that using longer buprenorphine/ naloxone taper schedules does not improve outcomes in opioid-dependent patients. No significant difference between the 7- and 28-day tapers in the proportion of patients with negative urine samples at the end of the taper (24.7% vs 18.8%) or after 1 (11.0% vs 11.5%) or 3 (6.7% vs 9.2%) months of follow-up have been noted. In terms of withdrawal and craving also there were no significant between-group differences in ARSW, COWS or VAS scores at the end of the taper or at 1 or 3 months follow-up. 34 The results of the study in adolescents and young adults demonstrated that in the shorter term, outcomes were generally better with a 12-week tapering schedule of buprenorphine/ naloxone therapy than with medically-supervised withdrawal therapy alone. However, in the longer term, there were no significant between-treatment differences in self-reported opioid use or injecting 35. Strategies 166

4 APRIL 2010 DELHI PSYCHIATRY JOURNAL Vol. 13 No.1 to help prevent relapse include offering supportive counselling and close monitoring for relapse following the tapering of buprenorphine/naloxone has been suggested as an option following taper in some patients 36. More data are needed concerning the potential of long-term maintenance therapy with buprenorphine/naloxone in adolescents. Retention In Treatment The favourable effect of buprenorphine/ naloxone on retention in treatment is supported by two retrospective, observational studies 37,38. Significantly (p < 0.001) more patients in the group receiving buprenorphine/naloxone short term taper treatment completed the medically supervised withdrawal programme compared with the two groups of patients treated with clonidine (84% vs 56% and 54%). Importantly, this study also showed that significantly (p < 0.001) more patients in the group receiving buprenorphine/naloxone short-term taper continued treatment (i.e. attended at least 1 day of an inpatient or outpatient treatment programme) following medically-supervised withdrawal compared with the two groups of patients treated with clonidine (83% vs 32% and 31%). 37 Special patient populations Buprenorphine/naloxone dosage should be adjusted in patients with hepatic impairment and patients should be closely monitored for symptoms of precipitated opioid withdrawal and in severe hepatic impairment it is contraindicated. 8 Buprenorphine/naloxone should be administered with caution in patients with severe renal impairment. No pharmacokinetic data for buprenorphine/ naloxone in elderly patients are available it should be administered with caution in these patients 16. Tolerability and side effects Buprenorphine/naloxone combination is generally well tolerated. Few differences between the adverse event profiles of buprenorphine/ naloxone and buprenorphine alone have been observed. 8 The 52-week trial of buprenorphine/ naloxone in maintenance therapy (n = 317) the overall rate of adverse events did not significantly differ between treatment groups; adverse events were reported in 78% of patients receiving buprenorphine/naloxone, 85% of buprenorphine alone recipients and 80% of placebo recipients. The most commonly reported adverse events in buprenorphine/naloxone recipients included headache, withdrawal syndrome, pain, nausea, insomnia and sweating. Withdrawal syndrome and diarrhoea occurred with a higher incidence in the placebo group and constipation occurred with a higher incidence in the buprenorphine/ naloxone and buprenorphine alone groups. Of the 472 patients included, 385 received at least 8 weeks treatment with buprenorphine/ naloxone and 261 received at least 6 months treatment. 23 Doses up to a total daily dose of 24 mg/6 mg were administered. Treatment was discontinued in 14 patients because of adverse events, of which withdrawal symptoms such as rhinitis and diarrhea were most common. ECG recordings and chemical and hematological tests did not reveal any clinically important changes from baseline. Treatment-related adverse events with buprenorphine/naloxone were reported for 342 of 472 patients (72.5%) and those that occurred in >10% of patients were insomnia, constipation, nausea, sweating, withdrawal syndrome and headache. Increases in hepatic ALT, AST or lactate dehydrogenase levels were the most common serious adverse events reported (ten patients) and were considered possibly or probably related to bupr enorphine/naloxone treatment in seven patients. Limited tolerability data are available versus active comparators other than buprenorphine alone. Versus clonidine in medically-supervised withdrawal treatment, the number of adverse events reported per patient per day was significantly fewer with buprenorphine/naloxone than clonidine in both the inpatient and outpatient settings. 32 The report of death due to respiratory failure was considered unrelated with the medication. Among the 18 serious adverse events that occurred in patients receiving buprenorphine/ naloxone across the two trials, only one (possible oesophageal tear associated with excessive hiccupping) was thought possibly related to buprenorphine/ naloxone. 31 Dosage and Administration Induction only be initiated in patients with objective and clear signs of withdrawal in order to 167

5 DELHI PSYCHIATRY JOURNAL Vol. 13 No.1 APRIL 2010 avoid precipitating withdrawal. The dosage of buprenorphine/naloxone should be individualized in order to keep the patient in treatment and effectively suppress opioid withdrawal effects. The dose adjustments should be progressive and occur in 2mg/0.5 mg or 4mg/1mg increments or decrements. The final maintenance dosage is likely to be in the range of 4mg/1mg to 24mg/6mg per day, depending on the individual. Target doses of 16 mg/4 mg per day have been recommended but the daily dose must not exceed 24 mg/6mg per day. 16,8 Available in India Buprenorphine 2 mg + Naloxone 0.5 mg sublingual tablets References 1. US Department of Health and Human Services. Clinical guidelines for the use of buprenorphine in the treatment of opioid addiction: a treament improvement protocol TIP 40 naabt.org/ links/tip_40_pdf. pdf. 2. Best SE, Oliveto AH, Kosten TR. Opioid addiction: recent advances in detoxification and maintenance therapy. CNS Drugs 1996; 6 (4): Srivastava A, Kahan M. Buprenorphine: a potential new treatment option for opioid dependence. CMAJ 2006; 174 (13) : Mattick RP, Kimber J, Breen C, et al. Buprenorphine maintenance versus placebo or methadone maintenance for opioid dependence. Cochrane Database Syst Rev 2003; (2) : CD Sullivan LE, Chawarski M, O Connor PG, et al. The practice of office-based buprenorphine treatment of opioid dependence: is it associated with new patients entering into treatment? Drug Alcohol Depend 2005; 79 (1) : Chapleo CB, Walter DS. The buprenorphinenaloxone combination product. Res Clin Forums 1997; 19 (2) : Mendelson J, Jones RT, Welm S, et al. Buprenorphine and naloxone combinations: the effects of three dose ratios in morphinestabilized, opiate-dependent volunteers. Psychopharmacol (Berl) 1999; 141 (1) : Reckitt Benckiser Pharmaceuticals, Inc. Suboxone (buprenorphine HCl and naloxone HCl dihydrate sublingual tablets)/subutex (buprenorphine HCl sublingual tablets): US prescribing information [online]. Available from URL: patients/pi/. 9. Strain EC, Walsh SL, Bigelow GE. Blockade of hydromorphone effects by buprenorphine/ naloxone and buprenorphine. Psychopharmacol (Berl) 2002 ; 159 (2): Comer SD, Walker EA, Collins ED. Buprenorphine/ naloxone reduces the reinforcing and subjective effects of heroin in heroin-dependent volunteers. Psychopharmacol (Berl) 2005; 181 (4): Correia CJ,Walsh SL, Bigelow GE, et al. Effects associated with double-blind omission of buprenorphine/naloxone over a 98-h period. Psychopharmacol (Berl) 2006; 189 (3): Weinhold LL, Preston KL, Farre M, et al. Buprenorphine alone and in combination with naloxone in non-dependent humans. Drug Alcohol Depend 1992 ; 30 (3): Rosado J, Walsh SL, Bigelow GE, et al. Sublingual buprenorphine/naloxone precipitated withdrawal in subjects maintained on 100mg of daily methadone. Drug Alcohol Depend 2007; 90 (2) : Mintzer MZ, Correia CJ, Strain EC. A doseeffect study of repeated administration of buprenorphine/naloxone on performance in opioid-dependent volunteers. Drug Alcohol Depend 2004; 74 (2): Elkader A, Sproule B. Buprenorphine: clinical pharmacokinetics in the treatment of opioid dependence. Clin Pharmacokinet 2005; 44 (7): European Medicines Agency. Suboxone: summary of product characteristics [online]. Available from URL: europa.eu/humandocs/pdfs/epar/suboxone/ H-697-PI-en.pdf. 17. Elkader A, Sproule B. Buprenorphine: clinical pharmacokinetics in the treatment of opioid dependence. Clin Pharmacokinet 2005; 44 (7): Pe r ez de los Cobos J, Martin S, Etcheberrigaray A, et al. A controlled trial of 168

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