Pharmacologic treatments for opioid dependence: detoxification and maintenance options

Treatment outcomes in opioid dependent patients with different buprenorphine/naloxone induction dosing patterns and trajectories

BACKGROUND AND OBJECTIVES

Induction is a crucial period of opioid addiction treatment. This study aimed to identify buprenorphine/naloxone (BUP) induction patterns and examine their association with outcomes (opioid use, retention, and related adverse events [AEs]).

METHODS

The secondary analysis of a study of opioid-dependent adults seeking treatment in eight treatment settings included 740 participants inducted on BUP with flexible dosing.

RESULTS

Latent class analysis models detected six distinctive induction trajectories: bup1-started and remained on low; bup2-started low, shifted slowly to moderate; bup3-started low, shifted quickly to moderate; bup4-started high, shifted to low; bup5-started and remained on moderate; bup6-started moderate, shifted to high dose (Fig. 1). Baseline characteristics, including Clinical Opioid Withdrawal Scale (COWS), were important predictors of retention. When controlled for the baseline characteristics, bup6 participants were three times less likely to drop out the first 7 days than bup1 participants (adjusted hazard ratio (aHR) = .28, p = .03). Opioid use and AEs were similar across trajectories. Participants on ≥16 mg BUP compared to those on <16 mg at Day 28 were less likely to drop out (aHR = .013, p = .001) and less likely to have AEs during the first 28 days (aOR = .57, p = .03).

DISCUSSION AND CONCLUSIONS

BUP induction dosing was guided by an objective measure of opioid withdrawal. Participants with higher baseline COWS whose BUP doses were raised more quickly were less likely to drop out in the first 7 days than those whose doses were raised slower.

SCIENTIFIC SIGNIFICANCE

This study supports the use of an objective measure of opioid withdrawal (COWS) during BUP induction to improve retention early in treatment.

Patient Perspectives Associated with Intended Duration of Buprenorphine Maintenance Therapy

Patients with opioid use disorders frequently discontinue opioid maintenance therapy (OMT) prematurely, reducing retention and possibly limiting the efficacy of OMT. The current study is a cross-sectional survey of patients (N=69) enrolled in buprenorphine maintenance therapy (BMT). We examined patient demographics, BMT characteristics (e.g., dose, time in BMT), and patient perspectives regarding intended duration of BMT. In addition, patients' reasons for continuing or discontinuing BMT were investigated. Results revealed that the majority (82%) of participants reported wanting to continue BMT for at least 12months. Age at first drug use, time in BMT, concern about pain, and concern about relapse were all positively associated with intended duration of BMT. The following were negatively associated with intended duration of BMT: recent discussion with a treatment provider about BMT discontinuation, prior attempt to discontinue BMT, concern about withdrawal symptoms, experiencing pleasurable effects from taking buprenorphine, and perceived conflicts of BMT with life, work, or school obligations. The most common reasons for wanting to continue BMT included concerns about withdrawal symptoms, relapse, and pain. Although preliminary, the findings highlight key issues with regard to patients' perspectives of BMT. The results of this study provide information that may be useful in improving OMT programs and treatment outcomes.

Characterizing opioid withdrawal during double-blind buprenorphine detoxification

BACKGROUND

Prescription opioid (PO) abuse has become an urgent public health issue in the United States. Detoxification is one important treatment option, yet relatively little is known about the time course and severity of opioid withdrawal during buprenorphine detoxification.

METHODS

This is a secondary analysis of data from a randomized, placebo-controlled, double-blind evaluation of 1, 2, and 4-week outpatient buprenorphine tapers among primary prescription opioid (PO) abusers. The aim is to characterize the time course and severity of buprenorphine withdrawal under rigorous, double-blind conditions, across multiple taper durations, and using multiple withdrawal-related measures (i.e., self-report and observer ratings, pupil diameter, ancillary medication utilization). Participants were PO-dependent adults undergoing buprenorphine detoxification and biochemically-verified to be continuously abstinent from opioids during their taper (N = 28).

RESULTS

Participants randomly assigned to the 4-week taper regimen experienced a relatively mild and stable course of withdrawal, with few peaks in severity. In contrast, the 1- and 2-week taper groups experienced stark increases in withdrawal severity during the week following the last buprenorphine dose, followed by declines in withdrawal severity thereafter. The 4-week taper group also reported significantly fewer disruptions in sleep compared to the other experimental groups. When predictors of withdrawal were examined, baseline ratings of "Expected Withdrawal Severity" was the most robust predictor of withdrawal experienced during the taper.

CONCLUSION

Data from this trial may inform clinicians about the expected time course, magnitude, and pattern of buprenorphine withdrawal and aid efforts to identify patients who may need additional clinical support during outpatient buprenorphine detoxification.

Discontinuation of buprenorphine maintenance therapy: perspectives and outcomes

Buprenorphine maintenance therapy (BMT) is increasingly the preferred opioid maintenance agent due to its reduced toxicity and availability in an office-based setting in the United States. Although BMT has been shown to be highly efficacious, it is often discontinued soon after initiation. No current systematic review has yet investigated providers' or patients' reasons for BMT discontinuation or the outcomes that follow. Hence, provider and patient perspectives associated with BMT discontinuation after a period of stable buprenorphine maintenance and the resultant outcomes were systematically reviewed with specific emphasis on pre-buprenorphine-taper parameters predictive of relapse following BMT discontinuation. Few identified studies address provider or patient perspectives associated with buprenorphine discontinuation. Within the studies reviewed providers with residency training in BMT were more likely to favor long term BMT instead of detoxification, and providers were likely to consider BMT discontinuation in the face of medication misuse. Patients often desired to remain on BMT because of fear of relapse to illicit opioid use if they were to discontinue BMT. The majority of patients who discontinued BMT did so involuntarily, often due to failure to follow strict program requirements, and 1 month following discontinuation, rates of relapse to illicit opioid use exceeded 50% in every study reviewed. Only lower buprenorphine maintenance dose, which may be a marker for attenuated addiction severity, predicted better outcomes across studies. Relaxed BMT program requirements and frequent counsel on the high probability of relapse if BMT is discontinued may improve retention in treatment and prevent the relapse to illicit opioid use that is likely to follow BMT discontinuation.

A placebo-controlled trial of dextromethorphan as an adjunct in opioid-dependent patients undergoing methadone maintenance treatment

BACKGROUND

Low-dose dextromethorphan (DM) might have anti-inflammatory and neurotrophic effects mechanistically remote from an NMDA receptor. In a randomized, double-blind, controlled 12 week study, we investigated whether add-on dextromethorphan reduced cytokine levels and benefitted opioid-dependent patients undergoing methadone maintenance therapy (MMT).

METHODS

Patients were randomly assigned to a group: DM60 (60mg/day dextromethorphan; n = 65), DM120 (120mg/day dextromethorphan; n = 65), or placebo (n = 66). Primary outcomes were the methadone dose required, plasma morphine level, and retention in treatment. Plasma tumor necrosis factor (TNF)-α, C-reactive protein, interleukin (IL)-6, IL-8, transforming growth factor-β1, and brain-derived neurotrophic factor (BDNF) levels were examined during weeks 0, 1, 4, 8, and 12. Multiple linear regressions with generalized estimating equation methods were used to examine the therapeutic effect.

RESULTS

After 12 weeks, the DM60 group had significantly longer treatment retention and lower plasma morphine levels than did the placebo group. Plasma TNF-α was significantly decreased in the DM60 group compared to the placebo group. However, changes in plasma cytokine levels, BDNF levels, and the methadone dose required in the three groups were not significantly different.

CONCLUSIONS

We provide evidence-decreased concomitant heroin use-of low-dose add-on DM's efficacy for treating opioid-dependent patients undergoing MMT.

Extended release naltrexone injection is performed in the majority of opioid dependent patients receiving outpatient induction: a very low dose naltrexone and buprenorphine open label trial

BACKGROUND

The approval of extended release injectable naltrexone (XR-NTX; Vivitrol(®)) has introduced a new option for treating opioid addiction, but studies are needed to identify its place within the spectrum of available therapies. The absence of physiological opioid dependence is a necessary and challenging first step for starting XR-NTX. Outpatient detoxification gives poor results and inpatient detoxification is either unavailable or too brief for the physiological effects of opioids to resolve. Here we present findings from an open label study that tested whether the transition from opioid addiction to XR-NTX can be safely and effectively performed in an outpatient setting using very low dose naltrexone and buprenorphine.

METHODS

Twenty treatment seeking opioid addicted individuals were given increasing doses of naltrexone starting at 0.25mg with decreasing doses of buprenorphine starting at 4 mg during a 7-day outpatient XR-NTX induction procedure. Withdrawal discomfort, craving, drug use, and adverse events were assessed daily until the XR-NTX injection, then weekly over the next month.

RESULTS

Fourteen of the 20 participants received XR-NTX and 13 completed weekly assessments. Withdrawal, craving, and opioid or other drug use were significantly lower during induction and after XR-NTX administration compared with baseline, and no serious adverse events were recorded.

CONCLUSIONS

Outpatient transition to XR-NTX combining upward titration of very low dose naltrexone with downward titration of low dose buprenorphine was safe, well tolerated, and completed by most participants. Further studies with larger numbers of subjects are needed to see if this approach is useful for naltrexone induction.

Determinants of the availability of hepatitis C testing services in opioid treatment programs: results from a national study

OBJECTIVES

We examined trends and organizational-level correlates of the availability of HCV testing in opioid treatment programs.

METHODS

We used generalized ordered logit models to examine associations between organizational characteristics of 383 opioid treatment programs from the 2005 and 2011 National Drug Abuse Treatment System Survey and HCV testing availability.

RESULTS

Between 2005 and 2011, the proportion of opioid treatment programs offering HCV testing increased but largely because of increases in off-site referrals rather than on-site testing. HCV testing availability was higher in opioid treatment programs affiliated with a hospital and those receiving federal funds. Opioid treatment programs providing both methadone and buprenorphine were more likely to offer any HCV testing, whereas opioid treatment programs providing only buprenorphine treatment were less likely to offer on-site testing. HCV testing availability was associated with more favorable staff-to-client ratios.

CONCLUSIONS

The increasing use of off-site referrals for HCV testing in opioid treatment programs likely limits opportunities for case finding, prevention, and treatment. Declines in federal funding for opioid treatment programs may be a key determinant of the availability of HCV testing in opioid treatment programs.

Pharmacological strategies for detoxification

Detoxification refers to the safe discontinuation from a substance of dependence and is distinct from relapse prevention. Detoxification usually takes between a few days and a few weeks to complete, depending on the substance being misused, the severity of dependence and the support available to the user. Psychosocial therapies alongside pharmacological treatments are essential to improve outcome. The dependencies considered in this overview are detoxification from opioids (with methadone, buprenorphine, α2-adrenoceptor agonists and adjunct medications), alcohol (with benzodiazepines, anti-glutamatergics and γ-aminobutyric acid (GABA)-ergic drugs), stimulants and cannabis (with no clear recommended pharmacological treatments), benzodiazepines (with dose tapering) and nicotine (with nicotine replacement therapy, antidepressants and partial agonists). Evidence is limited by a lack of controlled trials robust enough for review bodies, and more research is required into optimal treatment doses and regimes, alone and in combination.

Phase I study of injectable, depot naltrexone for the relapse prevention treatment of opioid dependence

BACKGROUND AND OBJECTIVES

We tested long-acting injectable depot naltrexone for its tolerability, pharmacokinetics, and safety in Phase I.

METHODS

The Phase I trial enrolled 36 healthy participants in two panels (A, B). In Panel A, 24 subjects were randomly assigned to the high-dosage group (400 mg naltrexone, n=6; placebo, n=6) or low-dosage group (200 mg naltrexone, n=6; placebo, n=6). In Panel B, 12 subjects were randomized to take six doses of monthly injectable naltrexone (400 mg) or placebo.

RESULTS

After a single injection of naltrexone 200 and 400 mg, means (SD) of naltrexone plasma concentrations were .57 (.28) ng/ml and 1.5 (.8) ng/ml 30 days post-injection. There was no effect of accumulation after multiple dosing. Eleven of 30 subjects (36.67%) who were administered injectable depot naltrexone reported a total of 12 adverse events (AEs). Seven of these 11 AEs were coded as possibly related with study medication. All treatment-related AEs were mild in severity. No serious treatment-related AEs occurred.

DISCUSSION AND CONCLUSIONS

This long-acting formulation of injectable depot naltrexone is well tolerated, results in constant plasma concentration of naltrexone for at least 1 month.

SCIENTIFIC SIGNIFICANCE

The tolerability and safety of long-acting injectable depot naltrexone are good.

Naltrexone with or without guanfacine for preventing relapse to opiate addiction in St.-Petersburg, Russia

BACKGROUND

Stress is a key precipitant to discontinuing naltrexone and relapsing to opiate abuse. Alpha-2 adrenergic agonists like guanfacine may reduce stress induced craving and have reduced opiate relapse in small clinical trials.

METHODS

This randomized, double blind double dummy placebo-controlled 6-month trial tested oral naltrexone with or without guanfacine for reducing stress and preventing opiate relapse. We randomized 301 patients to: naltrexone 50 mg/day+guanfacine 1 mg/day (n=75) (N/G), naltrexone+guanfacine placebo (N/P) (n=76), naltrexone placebo+guanfacine (n=75) (P/G), and double placebo (n=75) (P/P).

RESULTS

Among the 75 patients in each group the percentage still retained on naltrexone treatment at six months was: N/G 26.7%, N/P 19.7% (p=0.258 to N/G), P/G 6.7% (p<0.05 to both N groups), and P/P 10.7% (p=0.013 to N+G). Guanfacine reduced the severity of stress particularly at weeks 10 and 18. Adverse events (AE) were infrequent (4.7%) without group differences, with most common AEs: headache, poor appetite, insomnia, and dizziness.

CONCLUSIONS

Adding guanfacine to naltrexone did not improve treatment retention or opiate free urines, but it reduced both stress and craving at later time points in treatment, which may be related to stress-induced craving and the animal model of incubation of reinstatement. During treatment, HIV risk, anxiety, and depression reduced among all patients in treatment, regardless of group.

[Tobacco use and illicit substance use disorders: what should we have to do?]

Tobacco use is a commonplace phenomenon in our society. Its use is responsible for more death and disease than any other noninfectious cause. More deaths are caused each year by tobacco use than by all deaths from HIV, illegal drug use, alcohol use, motor vehicle injuries, suicides, and murders combined. Tobacco remains responsible for greater morbidity than alcohol and all other drugs combined. Tobacco dependence is highly prevalent among drug-dependent patients. Substance abuse patients smoke more and are more vulnerable to the effects of smoking than general populations. Traditional substance abuse therapeutic programs too frequently focus only on treatment of alcohol or other drugs rather than including treatment for tobacco dependence. Currently, there are no official medical recommendations for the treatment of tobacco addiction in illicit polysubstance users.

METHODS

A comprehensive literature search from a range of electronic databases (PubMed, Embase, PsycInfo, Google Scholar) was conducted for the period from 1988 to September 2012, using the following keywords alone or in combination: tobacco, nicotine, cocaine, cannabis, amphetamines, opiates, substance abuse, substance dependence, addiction, treatment. There were no restrictions on the identification or inclusion of studies in terms of publication status, language and design type.

RESULTS

Our literature review will focus on epidemiological, neurobiological, clinical interactions between tobacco, alcohol and other illicit drugs. It will also focus on therapeutic programs in this dual addictive disorder. The aim of this literature review is to make proposals for the treatment of tobacco addiction in polysubstance users entering in specific therapeutic programs.

Effects of prototypic calcium channel blockers in methadone-maintained humans responding under a naloxone discrimination procedure

Accumulating evidence suggests that L-type calcium channel blockers (CCBs) attenuate the expression of opioid withdrawal and the dihydropyridine L-type CCB isradipine has been shown to block the behavioral effects of naloxone in opioid-maintained humans. This study determined whether two prototypic L-type CCBs with differing chemical structures, the benzothiazepine diltiazem and the phenylalkamine verapamil, attenuate the behavioral effects of naloxone in methadone-maintained humans trained to distinguish between low-dose naloxone (0.15 mg/70 kg, i.m.) and placebo under an instructed novel-response drug discrimination procedure. Once discrimination was acquired, diltiazem (0, 30, 60, 120 mg) and verapamil (0, 30, 60, 120 mg), alone and combined with the training dose of naloxone, were tested. Diltiazem alone produced 33-50% naloxone- and novel-appropriate responding at 30 and 60 mg and essentially placebo-appropriate responding at 120 mg. Verapamil alone produced 20-40% naloxone- and 0% novel-appropriate responding. Diltiazem at 60 mg decreased several ratings associated with positive mood and increased VAS ratings of "Bad Drug Effects" relative to placebo, whereas verapamil increased ratings associated with euphoria. When administered with naloxone, diltiazem produced 94-100% naloxone-appropriate-responding with 6% novel-appropriate responding at 60 mg (n=3). When administered with naloxone, verapamil produced 60-80% naloxone- and 0% novel-appropriate responding (n=5). Diltiazem decreased diastolic blood pressure and heart rate whereas verapamil decreased ratings of arousal relative to placebo. These results suggest that CCBs with different chemical structures can be differentiated behaviorally, and that diltiazem and verapamil do not attenuate the discriminative stimulus effects of naloxone in humans at the doses tested.

Reinforcement of an alternative behavior as a model of recovery and relapse in the rat

A preclinical model that includes measures of alternative behavior and drug-seeking could improve our understanding of the processes involved in successful recovery; however current preclinical models of relapse do not measure alternative behavior. We assessed the persistence of food-maintained responding and the resumption of ethanol-maintained responding after ethanol-maintained responding was reduced by changing the response requirement for concurrently available food. Ethanol (10%, w/v) was always available following 5 responses (FR5). A 16 kHz tone indicating food delivery followed 150 responses (FR150) resulted in ethanol-predominate responding and substantial amounts of ethanol were earned (0.47 g/kg per 30-min session) and consumed. An 8 kHz tone indicating food delivery followed 5 responses (FR5) for 1, 2, 4, or 16 consecutive sessions reduced ethanol-maintained responding despite unchanged ethanol availability. Ethanol-maintained responding resumed upon subsequent presentation of the 16 kHz tone. However, more responses occurred on the food lever before 5 responses occurred on the ethanol lever as the number of preceding FR5 food sessions increased. These results suggest that alternative reinforcement may reduce control by discriminative stimuli that occasion ethanol-seeking and is consistent with the risk of relapse declining with longer periods of recovery because of the strengthening of alternative behavior.

Medication assisted treatment in US drug courts: results from a nationwide survey of availability, barriers and attitudes

Drug treatment courts are an increasingly important tool in reducing the census of those incarcerated for non-violent drug offenses; medication assisted treatment (MAT) is proven to be an effective treatment for opioid addiction. However, little is known about the availability of and barriers to MAT provision for opioid-addicted people under drug court jurisdiction. Using an online survey, we assessed availability, barriers, and need for MAT (especially agonist medication) for opioid addiction in drug courts. Ninety-eight percent reported opioid-addicted participants, and 47% offered agonist medication (56% for all MAT including naltrexone). Barriers included cost and court policy. Responses revealed significant uncertainty, especially among non-MAT providing courts. Political, judicial and administrative opposition appear to affect MAT's inconsistent use and availability in drug court settings. These data suggest that a substantial, targeted educational initiative is needed to increase awareness of the treatment and criminal justice benefits of MAT in the drug courts.

Comparison of cognitive performance in methadone maintenance patients with and without current cocaine dependence

BACKGROUND

There is evidence for psychomotor and cognitive performance impairment in methadone maintenance patients (MMP), as well as in individuals with current cocaine dependence. It is unknown whether MMP with concurrent cocaine dependence perform worse on tests of cognitive function than MMP without cocaine dependence.

METHODS

Performance was compared between MMP with and without current cocaine dependence (MMP/CD+; N = 53 and MMP/CD-; N = 24) on a standard battery of tasks designed to measure psychomotor performance, attention, episodic and working memory, and executive function.

RESULTS

Participant characteristics were mostly similar across groups. However, the MMP/CD+ group had a shorter duration of methadone treatment, and a larger percentage of participants with self-reported 30-day poly-substance abuse and positive urine drug tests on the day of cognitive testing. There were no differences between the groups on measures of balance, psychomotor coordination, divided attention, working memory, most measures of episodic memory, or executive function. Relative to MMP/CD-, MMP/CD+ showed significant impairment on select measures of psychomotor performance/attention (simple reaction time and trail-making test A) and episodic memory (higher false alarm rates on recognition memory).

CONCLUSIONS

The absence of differences between MMP/CD+ and MMP/CD- on measures of higher order cognitive functions, and the relatively small magnitude between-group differences on other measures suggest that current cocaine dependence, in the absence of cocaine intoxication, is unlikely to be associated with clinically meaningful increases in performance impairment in MMP.

Injectable extended-release naltrexone for opioid dependence: a double-blind, placebo-controlled, multicentre randomised trial

BACKGROUND

Opioid dependence is associated with low rates of treatment-seeking, poor adherence to treatment, frequent relapse, and major societal consequences. We aimed to assess the efficacy, safety, and patient-reported outcomes of an injectable, once monthly extended-release formulation of the opioid antagonist naltrexone (XR-NTX) for treatment of patients with opioid dependence after detoxification.

METHODS

We did a double-blind, placebo-controlled, randomised, 24-week trial of patients with opioid dependence disorder. Patients aged 18 years or over who had 30 days or less of inpatient detoxification and 7 days or more off all opioids were enrolled at 13 clinical sites in Russia. We randomly assigned patients (1:1) to either 380 mg XR-NTX or placebo by an interactive voice response system, stratified by site and gender in a centralised, permuted-block method. Participants also received 12 biweekly counselling sessions. Participants, investigators, staff , and the sponsor were masked to treatment allocation. The primary endpoint was the response profile for confirmed abstinence during weeks 5–24, assessed by urine drug tests and self report of non-use. Secondary endpoints were self-reported opioid-free days, opioid craving scores, number of days of retention, and relapse to physiological opioid dependence. Analyses were by intention to treat. This trial is registered at ClinicalTrials.gov, NCT00678418.

FINDINGS

Between July 3, 2008, and Oct 5, 2009, 250 patients were randomly assigned to XR-NTX (n=126) or placebo (n=124). The median proportion of weeks of confirmed abstinence was 90·0% (95% CI 69·9–92·4) in the XR-NTX group compared with 35·0% (11·4–63·8) in the placebo group (p=0·0002). Patients in the XR-NTX group self-reported a median of 99·2% (range 89·1–99·4) opioid-free days compared with 60·4% (46·2–94·0) for the placebo group (p=0·0004). The mean change in craving was –10·1 (95% CI –12·3 to –7·8) in the XR-NTX group compared with 0·7 (–3·1 to 4·4) in the placebo group (p<0·0001). Median retention was over 168 days in the XR-NTX group compared with 96 days (95% CI 63–165) in the placebo group (p=0·0042). Naloxone challenge confirmed relapse to physiological opioid dependence in 17 patients in the placebo group compared with one in the XR-NTX group (p<0·0001). XR-NTX was well tolerated. Two patients in each group discontinued owing to adverse events. No XR-NTX-treated patients died, overdosed, or discontinued owing to severe adverse events.

INTERPRETATION

XR-NTX represents a new treatment option that is distinct from opioid agonist maintenance treatment. XR-NTX in conjunction with psychosocial treatment might improve acceptance of opioid dependence pharmacotherapy and provide a useful treatment option for many patients.

FUNDING

Alkermes.

Use of naltrexone to treat opioid addiction in a country in which methadone and buprenorphine are not available

Opioid dependence is one of the most severe drug dependencies. Naltrexone is a medication that completely blocks the subjective and other effects of opioids and, when administered to detoxified opioid addicts and taken as directed, prevents relapse and helps maintain abstinence. The major problem with naltrexone is poor compliance, particularly in countries in which there is a treatment alternative based on substitution of illicit opioids such as heroin with orally administered opioid agonists (methadone) or partial agonist/antagonists (buprenorphine). In Russia, substitution therapy is forbidden by law, and naltrexone is the only available pharmacotherapy for heroin dependence. Due to the lack of alternatives to naltrexone and stronger family control of compliance (adherence), naltrexone is more effective for relapse prevention and abstinence stabilization in Russia than in Western countries. Long-acting, sustained-release formulations (injectable and implantable) seem particularly effective compared with oral formulations. This article summarizes the results of studies conducted in Russia during the past 10 years that demonstrate these points.

Pain and opioids

A szövetkárosító hatású ingerek fájdalomérzetet váltanak ki, megvédve a szervezetet a káros behatásoktól, illetve felhívják a figyelmünket a szervezet kórfolyamataira. Fájdalomreceptorok (nociceptorok) a szervezetünkben mindenhol megtalálhatók. A fájdalom védekezőmechanizmusokat indít be, így vegetatív és motoros reflexválaszokat, illetve érzelmekkel, viselkedéssel kapcsolatos válaszokat vált ki. A krónikus fájdalom azonban gyakorlatilag haszontalan, kóros pszichés állapotokhoz vezethet. Fájdalomcsillapításra számos lehetőség van, beleértve nemszteroid gyulladásgátlókat, opioidokat, idegsebészeti beavatkozásokat, valamint noninvazív kezelésmódokat. Az opioidok centrális és periferiális farmakológiai hatásait elsősorban a központi idegrendszer és a gastrointestinalis rendszer opioidreceptorai közvetítik. A fájdalomcsillapítás a központi idegrendszer különböző szintjein jön létre, és két módon befolyásolhatja a fájdalomérzést: gátolja a fájdalom percepcióját, illetve megváltoztatja az érzelmi reakciókat. Opioidok használata indikált posztoperatív fájdalmakban, neuropathiás fájdalomban, illetve tumoros megbetegedésekben. Az opioidok használatakor azonban számolni kell a kellemetlen mellékhatásokkal is, így légzésbénító hatásával, valamint a kialakuló toleranciával és dependenciával, amely nem teszi az opioidokat optimális fájdalomcsillapítókká. Annak érdekében, hogy rendelkezésre álljon egy optimális opioid fájdalomcsillapító, a mai napig kutatások folynak mind magyar, mind külföldi laboratóriumokban. Továbbá az opioidoknak eufóriát okozó hatásuk miatt nagy az abúzuspotenciálja, ami sürgetővé teszi a gyógyszerfüggőség molekuláris mechanizmusának feltárását. Mindezek fényében nagy jelentősége van az opioidok kutatásának.