Analgesic responses to morphine and placebo in individuals with postoperative pain

Creating Placebo Nonresponders in the Lab

Conditioning and expectation are known to be the main mechanisms of placebo analgesia. They may operate together, so that expectations may be enhanced by a conditioning procedure. Although most of the studies have tried to potentiate expectations through conditioning in order to generate good placebo responders, a few studies have tried to mismatch conditioning and expectations in order to investigate the subsequent administration of a placebo. In this study, we want to further investigate this mismatch. We generated incongruent associations during a conditioning procedure in which the study participants did not get what they expected. In fact, although the participants received verbal instructions of pain decrease following the administration of a placebo, we surreptitiously increased the painful electric stimulation. Two pairings of these incongruent associations (mismatch between what was expected and what was experienced) disrupted expectations of analgesia as well as the placebo effect, as assessed by measuring electric pain thresholds on the hand. The effects of mismatch conditioning on the hand extended to the contralateral arm and to a different type of pain (tourniquet), which suggests that local mismatch conditioning may affect the whole body. In all cases, expectations predicted placebo analgesia. These findings indicate that placebo nonresponders can be created in the laboratory by acting on expectations and that local effects can be generalized to other parts of the body. They also stress the importance of expectations in the therapeutic outcome, with important implications for clinical trials. PERSPECTIVE: By using mismatch conditioning, in which study participants did not get what they expected, we reduced expectations of analgesia, and this reduction abolished placebo analgesia. This effect extended to other parts of the body and other types of pain, which indicates that placebo nonresponders can be created in the laboratory.

IUPHAR review: Navigating the role of preclinical models in pain research

Chronic pain is a complex and challenging medical condition that affects millions of people worldwide. Understanding the underlying mechanisms of chronic pain is a key goal of preclinical pain research so that more effective treatment strategies can be developed. In this review, we explore nociception, pain, and the multifaceted factors that lead to chronic pain by focusing on preclinical models. We provide a detailed look into inflammatory and neuropathic pain models and discuss the most used animal models for studying the mechanisms behind these conditions. Additionally, we emphasize the vital role of these preclinical models in developing new pain-relief drugs, focusing on biologics and the therapeutic potential of NMDA and cannabinoid receptor antagonists. We also discuss the challenges of TRPV1 modulation for pain treatment, the clinical failures of neurokinin (NK)- 1 receptor antagonists, and the partial success story of Ziconotide to provide valuable lessons for preclinical pain models. Finally, we highlight the overall success and limitations of current treatments for chronic pain while providing critical insights into the development of more effective therapies to alleviate the burden of chronic pain.

Ligand-Free Signaling of G-Protein-Coupled Receptors: Relevance to μ Opioid Receptors in Analgesia and Addiction

Numerous G-protein-coupled receptors (GPCRs) display ligand-free basal signaling with potential physiological functions, a target in drug development. As an example, the μ opioid receptor (MOR) signals in ligand-free form (MOR-μ*), influencing opioid responses. In addition, agonists bind to MOR but can dissociate upon MOR activation, with ligand-free MOR-μ* carrying out signaling. Opioid pain therapy is effective but incurs adverse effects (ADRs) and risk of opioid use disorder (OUD). Sustained opioid agonist exposure increases persistent basal MOR-μ* activity, which could be a driving force for OUD and ADRs. Antagonists competitively prevent resting MOR (MOR-μ) activation to MOR-μ*, while common antagonists, such as naloxone and naltrexone, also bind to and block ligand-free MOR-μ*, acting as potent inverse agonists. A neutral antagonist, 6β-naltrexol (6BN), binds to but does not block MOR-μ*, preventing MOR-μ activation only competitively with reduced potency. We hypothesize that 6BN gradually accelerates MOR-μ* reversal to resting-state MOR-μ. Thus, 6BN potently prevents opioid dependence in rodents, at doses well below those blocking antinociception or causing withdrawal. Acting as a ‘retrograde addiction modulator’, 6BN could represent a novel class of therapeutics for OUD. Further studies need to address regulation of MOR-μ* and, more broadly, the physiological and pharmacological significance of ligand-free signaling in GPCRs.

An Active Inference Account of Touch and Verbal Communication in Therapy

This paper offers theoretical explanations for why “guided touch” or manual touch with verbal communication can be an effective way of treating the body (e.g., chronic pain) and the mind (e.g., emotional disorders). The active inference theory suggests that chronic pain and emotional disorders can be attributed to distorted and exaggerated patterns of interoceptive and proprioceptive inference. We propose that the nature of active inference is abductive. As such, to rectify aberrant active inference processes, we should change the “Rule” of abduction, or the “prior beliefs” entailed by a patient’s generative model. This means pre-existing generative models should be replaced with new models. To facilitate such replacement—or updating—the present treatment proposes that we should weaken prior beliefs, especially the one at the top level of hierarchical generative models, thereby altering the sense of agency, and redeploying attention. Then, a new prior belief can be installed through inner communication along with manual touch. The present paper proposes several hypotheses for possible experimental studies. If touch with verbal guidance is proven to be effective, this would demonstrate the relevance of active inference and the implicit prediction model at a behavioral level. Furthermore, it would open new possibilities of employing inner communication interventions, including self-talk training, for a wide range of psychological and physical therapies.

What is the role of placebo in neurotherapeutics?

INTRODUCTION

The widespread use of the word 'placebo' in the medical literature emphasizes the importance of this phenomenon in modern biomedical sciences. Neuroscientific research over the past thirty years shows that placebo effects are genuine psychobiological events attributable to the overall therapeutic context, and can be robust in both laboratory and clinical settings.

AREAS COVERED

Here the authors describe the biological mechanisms and the clinical implications of placebo effects with particular emphasis on neurology and psychiatry, for example in pain, movement disorders, depression. In these conditions, a number of endogenous systems have been identified, such as endogenous opioids, endocannabinoids, and dopamine, which contribute to the placebo-induced benefit.

EXPERT OPINION

Every effort should be made to maximize the placebo effect and reduce its evil twin, the nocebo effect, in medical practice. This does not require the administration of a placebo, but rather the enhancement of the effects of pharmacological and nonpharmacological treatments through a good doctor-patient interaction.

Thirty Years of Neuroscientific Investigation of Placebo and Nocebo: The Interesting, the Good, and the Bad

Over the past 30 years there has been a surge of research on the placebo effect using a neuroscientific approach. The interesting aspects of this effort are related to the identification of several biological mechanisms of both the placebo and nocebo effects, the latter of which is defined as a negative placebo effect. Some important translational implications have emerged both in the setting of clinical trials and in routine medical practice. One of the principal contributions of neuroscience has been to draw the attention of the scientific and medical communities to the important role of psychobiological factors in therapeutic outcomes, be they drug related or not. Indeed, many biological mechanisms triggered by placebos and nocebos resemble those modulated by drugs, suggesting a possible interaction between psychological factors and drug action. Unfortunately, this new knowledge regarding placebos has the potential of being dangerously exploited by pseudoscience. Expected final online publication date for the Annual Review of Pharmacology and Toxicology, Volume 62 is January 2022. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

Historical Controls in Randomized Clinical Trials: Opportunities and Challenges

Randomized control trials (RCTs) with placebo are the gold standard for determining efficacy of novel pharmaceutical treatments. Since their inception, over 75 years ago, researchers have amassed a large body of underutilized data on outcomes in the placebo control arms of these trials. Although rare disease indications have used these historical placebo data as synthetic controls to reduce burden on patients and accelerate drug discovery, broad use of historical controls is in its infancy. Large-scale historical placebo data could be leveraged to benefit both drug developers and patients if warehoused and made more available to guide trial design and analysis. Here, we examine challenges in utilizing historical controls related to heterogeneity in trial design, outcome ascertainment, patient characteristics, and unmeasured pharmacogenomic effects. We then discuss the advantages and disadvantages of current approaches and propose a path forward to broader use of historical controls in RCTs.

Better than nothing: A historical account of placebos and placebo effects from modern to contemporary medicine

Throughout the history of medicine, multiple conceptions of "placebo" and "placebo effect" have often co-existed across different domains, and today the meaning of these concepts is still disputed. Against this background, this chapter provides a succinct account of the key events in the history of the concepts of "placebo," "placebo control," and "placebo effect." The first section reconstructs the etymology of the term "placebo" and its first introduction in medicine. The next sections provide an account of how placebos have been employed in both medical practice and scientific research in modern medicine. Later sections trace the emergence of the concepts of "placebo control" and "placebo effect" in the first half of the 20th century, from the first empirical studies investigating the effects of placebos up to the publication of Beecher's landmark article "The Powerful Placebo." Finally, the last two sections review the varieties of randomized, placebo-controlled trials (RCTs) in the second half of the 20th century, and the subsequent wave of empirical studies that, starting from the 1970s, have investigated the psychological, pharmacological and neurobiological mechanisms of placebo effects.

Drug-Placebo Additivity in Randomized Clinical Trials

In randomized clinical trials (RCTs), it is assumed that nonspecific effects beyond action of pharmacological agents are roughly equivalent in drug and placebo treatment groups. Hence, since the inception of RCTs, drug efficacy is determined by comparing outcomes in active to those in placebo control arms. However, quantitation of efficacy is based on an unproven assumption, that drug and placebo responses are always additive. Response to treatment in RCTs can be differentially influenced by the perturbing effects of patient expectations, side effects, and pharmacogenomic interactions in both drug and placebo arms. Ability to control for these effects requires understanding of when and where they arise, how to mitigate, analyze, and even leverage their impact. Here, we examine three factors that influence additivity: expectation, side effects, and pharmacogenomics. Furthermore, to provide novel insights into nonadditivity and solutions for managing it, we introduce systems pharmacogenomics, a network approach to integrating and analyzing the effects of the numerous interacting perturbations to which a patient is exposed in RCTs.

Opioid induced adrenal insufficiency: what is new?

PURPOSE OF REVIEW

Despite the declaration of an opioid epidemic, opioid use remains prevalent. Side-effects of chronic opioid use continue to be problematic. Opioid-induced endocrinopathies have been well documented, yet opioid-induced adrenal insufficiency (OIAI) remains underappreciated. This review summarizes what is currently known regarding the prevalence, predictive factors for the development and effect of treatment of OIAI.

RECENT FINDINGS

Although several case reports have highlighted the development of adrenal crisis among those receiving chronic opioids, only a few studies have systematically assessed patients for OIAI. The heterogeneity of these small studies presents challenges when trying to assess prevalence of or potential risk factors for OIAI. The estimated prevalence of OIAI among those treated with chronic opioids ranges from 8.3 to 29% and is more likely in those receiving higher doses of opioids. Reduced health-related quality of life variables and altered pain perception has been associated with lower cortisol levels; however, the effect of glucocorticoid replacement on the parameters remains unknown.

SUMMARY

Further research is critical to better identify those at greatest risk and guide optimal management of OIAI. Frontline providers should remain vigilant for possibility of OIAI among chronic opioid users.

[Placebo and nocebo : How can they be used or avoided?]

The expectations of patients enhance the probability of their occurrence and are thereby the main triggers for inducing placebo and nocebo responses. Strong placebo effects are not only regularly observed in pharmaceutical and non-pharmaceutical sham treatment in placebo controlled studies but also make a considerable contribution to any real treatment. The accompanying words are essential to ensure maximum impact of drugs and other forms of treatment. They should contain positive expressions instead of negations. Such a strengthening of drug therapy by placebo effects is more important than the widespread use of placebos that remains a problem because of the obligation to provide information and effective therapy and because of inherently induced side effects. Any false comments about symptoms or side effects can aggravate or induce them. Nocebo effects are not imagined but real symptoms that can definitely be harmful. They constitute a considerable proportion of the side effects requiring treatment. Awareness and knowledge is needed to prevent or neutralize them. Nocebo effects are avoidable when risk information is always directly combined with positive aspects, such as the expected benefits of the treatment or the prophylactic measures and therapeutic options for side effects. Existing negative expectations are disrupted by providing more alternative options and by leaving negative experiences in the past where they belong. Placebo and nocebo effects are strongly sensitive to the context. They are dependent on the experiences and conceptions of the individual patient, as well as on the physician-patient relationship. The latter can provide the best protection against harm from risk disclosure. In addition, the expectations of patients and their consequences are strongly affected by the expectations of the treating doctor, by fellow patients, the media and society.

Placebo acceptability in chronic pain patients: More dependent on application mode and resulting condition than on individual factors

Introduction

Placebo effects can be very effective in certain pain conditions, but their use is still highly controversial. Several studies show that patients would accept a placebo treatment under certain circumstances, particularly when they are informed prior to the treatment or when there are no effective treatment alternatives. This study examines the question, which factors influence the degree of acceptability of a hypothetical placebo application.

Methods

Patients filled in a questionnaire dealing with placebo applications. Moreover general data, diagnosis, duration of pain, pain ratings and anxiety/depression/stress scores, sleep disorders and opioid intake were collected from the patients` charts. 129 patients (44 men / 85 women, mean age 51.5 years, 18.0–80.9 years) entered the study. All patients had chronic pain syndromes and were treated in an universitary academic interdisciplinary pain center. Mean duration of pain was 14.7 years.

Results

The study did not show significant differences in placebo acceptability among patients with different pain diagnoses or accompanying psychological diagnoses or disorders. Hidden placebo application was considered much more unacceptable for the patients than the enhanced placebo or the open placebo application. An improved condition was associated with less feeling of deception, more trust and less negative mood than an unchanged or worsened condition.

Conclusion

Acceptance of placebo as pain therapy is much more dependent on the way of application (hidden or open) or on the resulting condition (improved, unchanged or worsened) than on factors inherent in the individual patients.

Placebo effects and racial and ethnic health disparities: an unjust and underexplored connection

While a significant body of bioethical literature considers how the placebo effect might introduce a conflict between autonomy and beneficence, the link between justice and the placebo effect has been neglected. Here, we bring together disparate evidence from the field of placebo studies and research on health inequalities related to race and ethnicity, and argue that, collectively, this evidence may provide the basis for an unacknowledged route by which health disparities are exacerbated. This route is constituted by an uneven distribution of placebo effects, resulting from differences in expressions of physician warmth and empathy, as well as support and patient engagement, across racial and ethnic lines. In a discussion of the ethical implications of this connection, we argue that this contribution to health disparities is a source of injustice, consider ways in which these disparities might be ameliorated and suggest that this conclusion is likely to extend to other realms of inequality as well.

Perceptions of French general practitioners and patients regarding dextropropoxyphene withdrawal: a qualitative study

OBJECTIVES

Dextropropoxyphene (DXP), a step 2 analgesic commonly prescribed in France, was withdrawn from the French market in 2011 following a European decision due to its poor risk-benefit ratio. The purpose of this study was to explore the perceptions of French general practitioners (GPs) and patients regarding DXP withdrawal.

DESIGN

Qualitative study based on 26 individual semi-structured interviews.

SETTING

Rhône-Alpes region of France.

PARTICIPANTS

Thirteen patients and 13 GPs.

METHODS

Interviews were conducted to collect data concerning the status of DXP, its efficacy and safety, the conditions of DXP's withdrawal and its potential impact. The transcripts were analysed using NVivo software.

RESULTS

DXP was a very popular drug among both patients and GPs. Its withdrawal was a bad experience for patients and many GPs; these misunderstood the reasons for its withdrawal and several contested them. They generally recognised more benefits than risks of DXP and considered alternative drugs unsatisfactory. In the same period, a French court case regarding another drug led to distrust towards the pharmaceutical industry and healthcare institutions, which contributed to the negative feelings reported. However, the experience was positive for the GPs who had been alerted to the poor DXP risk-benefit ratio well before its withdrawal.

CONCLUSIONS

Apart from physicians who were previously informed of its poor risk-benefit ratio, DXP withdrawal was not a good experience for patients and GPs. Better anticipation by the health authorities, in terms of pharmacoepidemiological surveillance and communication to healthcare professionals as well as the general public, should provide better acceptance of such a decision in the future.

Choose Your Words Wisely: The Impact of Message Framing on Patients' Responses to Treatment Advice

Other people's words can have a powerful influence on how we interpret our environment, what we expect and experience, what we value, how we feel, what we choose, and how we behave. Placebo (and nocebo) effects are a dramatic example of this. The way in which healthcare professionals discuss, describe, and inform patients about the characteristic effects of a given disease and it prevention, diagnosis and treatment influence patients' feelings and expectations which in turn affects their psychobiological responses to, and subjective experiences and outcomes of the disease and its treatment effects. The effect of clinicians' words on patients' responses to treatments and procedures, both active and inert or sham is nothing less than incredible. The way in which information about treatment effects is delivered to patients can even reverse the clinically proven effects of an active treatment, or increase the adverse effects of it. In this chapter, we begin by presenting the data on the impact of message framing on affect and expectations of health care in experimental situations followed by the evidence that indicates how various patient, disease and clinician related factors modify framing effects in the clinic. Finally we discuss how framing effects affect clinical practice. They can be leveraged to enhance placebo effects and minimize nocebo effects. They can provide strategies to assist shared-decision making in the face of complex uncertainty. Going forward, automation of health care and artificial intelligence may change the delivery of health care but patients will continue to be humans seeking health gains while avoiding health losses and how the information is presented will always be susceptible to framing effects.

Mindsets Matter: A New Framework for Harnessing the Placebo Effect in Modern Medicine

The clinical utility of the placebo effect has long hinged on physicians deceptively administering an objective placebo treatment to their patients. However, the power of the placebo does not reside in the sham treatment itself; rather, it comes from the psychosocial forces that surround the patient and the treatment. To this end, we propose a new framework for understanding and leveraging the placebo effect in clinical care. In outlining this framework, we first present the placebo effect as a neurobiological effect that is evoked by psychological processes. Next, we argue that along with implicit learning and expectation formation, mindsets are a key psychological process involved in the placebo effect. Finally, we illustrate the critical role of the social environment and treatment context in shaping these psychological processes. In doing so, we offer a guide for how the placebo effect can be understood, harnessed, and leveraged in the practice of modern medicine.

The placebo effect on resting tremor in Parkinson's disease: an electrophysiological study

INTRODUCTION

The aim of our study was to investigate the effect of apomorphine and placebo on resting tremor in tremor-dominant Parkinson's disease (tPD) patients.

METHODS

Fifteen tPD patients were enrolled. Each patient underwent two treatments on two consecutive days: on day one the patients received a subcutaneous injection of placebo, while on day two they received apomorphine. On each day, the patients underwent three electrophysiological recording sessions: T0, T1, and T2: before, 30 min, and 60 min after the treatment respectively. Electrophysiological changes in tremor amplitude were evaluated using a triaxial accelerometer.

RESULTS

Placebo was effective in improving resting tremor in all tPD patients (p = 0.009) at T1, but not at T2. Eight out of 15 tPD patients (53.3%) responded to placebo with an at least 70% reduction in tremor amplitude compared to the basal condition (responders). By contrast, seven out of 15 tPD patients (46.7%) did not show any variation in tremor amplitude after placebo administration (non-responders). Apomorphine induced a marked reduction in tremor amplitude at 30 min and 60 min in all investigated tPD patients. Of note, the decrease in tremor amplitude in placebo responders was similar to that achieved with dopaminergic stimulation induced by apomorphine.

CONCLUSIONS

Our study demonstrates that placebo was very effective in reducing resting tremor in about half of patients with tPD. The decrease in tremor amplitude in placebo responders was similar to that induced by apomorphine. The cerebral mechanisms underlying the placebo effect on resting tremor need further investigations.

Expectancy Reduces Symptoms but not Functional Impairment Following Exercise-induced Musculoskeletal Injury

OBJECTIVES

To quantify the extent to which the participant-provider interaction influences the response to sham treatment following exercised-induced acute musculoskeletal pain.

MATERIALS AND METHODS

In total, 40 participants between the ages of 18 and 35 volunteered for the study. Participants came to the laboratory for 3 test sessions 48-hour apart (day 1, 3, and 5). During the initial session, baseline measures were assessed and participants underwent a fatigue protocol for the biceps brachii. Participants were then assigned to a positive expectation or a no-expectation condition before receiving a sham laser therapy treatment. The positive expectation group received symptom improvement priming before their sham treatment. Participants allocated to the no-expectation condition received no feedback before the sham treatment. Maximum voluntary isometric contraction; relaxed elbow angle; visual analog scale; and the QuickDash questionnaire were used as outcome measures.

RESULTS

The positive expectation group had a significant reduction in perceived pain compared with the no-expectation group at day 3 follow-up, with the mean scores being 34.65 mm (SE=4.44) compared with 49.4 mm (SE=5.79), respectively. There were no between-group differences with respect to maximum voluntary isometric contraction, QuickDash, or relaxed elbow angle outcomes. In addition, there were no significant between-group differences observed with expected pain on follow-up visits, the effect sizes were d=0.26 on day 1 for day 3 and d=0.51 on day for day 5.

DISCUSSION

Positive expectations before a sham treatment enhanced reduction in pain intensity but did not improve functional impairments following exercise-induced acute musculoskeletal injury.

Nature of the placebo and nocebo effect in relation to functional neurologic disorders

Placebos have long been considered a nuisance in clinical research, for they have always been used as comparators for the validation of new treatments. By contrast, today they represent an active field of research, and, due to the involvement of many mechanisms, the study of the placebo effect can actually be viewed as a melting pot of concepts and ideas for neuroscience. There is not a single placebo effect, but many, with different mechanisms across different medical conditions and therapeutic interventions. Expectation, anxiety, and reward are all involved, as well as a variety of learning phenomena and genetic variants. The most productive models to better understand the neurobiology of the placebo effect are pain and Parkinson's disease. In these medical conditions, several neurotransmitters have been identified, such as endogenous opioids, cholecystokinin, dopamine, as well as lipidic mediators, for example, endocannabinoids and prostaglandins. Since the placebo effect is basically a psychosocial context effect, these data indicate that different social stimuli, such as words and therapeutic rituals, may change the chemistry of the patient's brain, and these effects are similar to those induced by drugs.

Contextually Aided Recovery (CARe): a scientific theory for innate healing

BACKGROUND

The chiropractic profession emerged when scientific explanations for causes of health and disease were still in infancy and the co-existence of notions such as innate healing and vitalism were perhaps admissible within such a historical context. Notwithstanding, within the scientific culture of the 21^st Century all healthcare paradigms require evidential support which in regard these early concepts are in large part, absent. Nevertheless, a large body of emerging scientific evidence supports the existence of innate healing phenomena that may explain a plethora of clinical outcomes observed during chiropractic care. However, in contrast to the notion that removing the putative subluxation constitutes the mechanism by which this healing is initiated, the evidentially supported explanation is one that invokes the impact of contextual factors inherent in the skilful care and authority of the healthcare provider. This perspective is presented here as the scientific model of Contextually Aided Recovery (CARe).

MAIN BODY

This paper contends that;Contextual effects are powerful and desirable and are triggered by contextual factors present in all therapeutic encounters including those encountered in chiropractic practice.These factors can elicit large clinical effects with substantive evidence supporting pain, immune and motor modulation.The compartmentalisation of specific and non-specific effects is a biologically and scientifically false dichotomy, erroneously invoked to de-legitimise treatment approaches that expertly construct contextual healing scenarios.The use of factors to construct contextual healing scenarios that maximise positive (placebo) and minimize negative (nocebo) effects is a skilful clinical art within the multimodal approach that describes modern chiropractic care and should be presented and defended as a legitimate component of orthodox healthcare Clinical improvement during chiropractic care, beyond any biologically specific treatment effects of manipulation and other modalities, may be largely understood considering contextual factors as described by a Contextually Aided Recovery (CARe) model.

Brain Connectivity Predicts Placebo Response across Chronic Pain Clinical Trials

Placebo response in the clinical trial setting is poorly understood and alleged to be driven by statistical confounds, and its biological underpinnings are questioned. Here we identified and validated that clinical placebo response is predictable from resting-state functional magnetic-resonance-imaging (fMRI) brain connectivity. This also led to discovering a brain region predicting active drug response and demonstrating the adverse effect of active drug interfering with placebo analgesia. Chronic knee osteoarthritis (OA) pain patients (n = 56) underwent pretreatment brain scans in two clinical trials. Study 1 (n = 17) was a 2-wk single-blinded placebo pill trial. Study 2 (n = 39) was a 3-mo double-blinded randomized trial comparing placebo pill to duloxetine. Study 3, which was conducted in additional knee OA pain patients (n = 42), was observational. fMRI-derived brain connectivity maps in study 1 were contrasted between placebo responders and nonresponders and compared to healthy controls (n = 20). Study 2 validated the primary biomarker and identified a brain region predicting drug response. In both studies, approximately half of the participants exhibited analgesia with placebo treatment. In study 1, right midfrontal gyrus connectivity best identified placebo responders. In study 2, the same measure identified placebo responders (95% correct) and predicted the magnitude of placebo's effectiveness. By subtracting away linearly modeled placebo analgesia from duloxetine response, we uncovered in 6/19 participants a tendency of duloxetine enhancing predicted placebo response, while in another 6/19, we uncovered a tendency for duloxetine to diminish it. Moreover, the approach led to discovering that right parahippocampus gyrus connectivity predicts drug analgesia after correcting for modeled placebo-related analgesia. Our evidence is consistent with clinical placebo response having biological underpinnings and shows that the method can also reveal that active treatment in some patients diminishes modeled placebo-related analgesia. Trial Registration ClinicalTrials.gov NCT02903238 ClinicalTrials.gov NCT01558700.

Placebo Use in Pain Management: A Mechanism-Based Educational Intervention Enhances Placebo Treatment Acceptability

Health care providers use treatments whose effectiveness derives partially or completely from 'nonspecific' factors, frequently referred to as placebo effects. Although the ethics of interventional placebo use continues to be debated, evidence suggests that placebos can produce clinically meaningful analgesic effects. Burgeoning evidence suggest that patients with chronic pain might be open to placebo treatments in certain contexts despite limited knowledge of their well-established psychoneurobiological underpinnings. In this investigation we sought to examine the effects of a brief, mechanism-based placebo analgesia educational intervention on aspects placebo knowledge and acceptability. Participants with chronic musculoskeletal pain completed a web-based survey in which they rated their knowledge of placebo analgesia, assessed placebo acceptability across different medical contexts, and evaluated 6 unique patient-provider treatment scenarios to assess the role of treatment effectiveness and deception on patient-provider attributions. Using a pre-post design, participants were randomized to receive either a placebo educational intervention or an active control education. Results showed that the educational intervention greatly improved perceptions of placebo knowledge, effectiveness, and acceptability, even in deceptive treatment contexts. This was the first study of its kind to show the value of an educational intervention in increasing openness to and knowledge of placebo analgesic interventions among patients with chronic musculoskeletal pain.

PERSPECTIVE

In this we article highlight how patients with chronic pain might be open to placebo interventions, particularly adjunct and/or complementary treatments, when provided education on the neurobiological and psychological mechanisms that underlie placebo effects. Study findings highlight ethically acceptable ways to potentially use placebo factors to enhance existing pain treatments and improve patient health outcomes.

The placebo effect: From concepts to genes

Despite its initial treatment as a nuisance variable, the placebo effect is now recognized as a powerful determinant of health across many different diseases and encounters. This is in light of some remarkable findings ranging from demonstrations that the placebo effect significantly modulates the response to active treatments in conditions such as pain, anxiety, Parkinson's disease, and some surgical procedures. Here, we review pioneering studies and recent advances in behavioral, neurobiological, and genetic influences on the placebo effect. Consistent with recent conceptualizations, the placebo effect is presented as the product of a general expectancy learning mechanism in which verbal, conditioned, and social cues are centrally integrated to change behaviors and outcomes. Examples of the integration of verbal and conditioned cues, such as instructed reversal of placebo effects are also incorporated into this model. We discuss neuroimaging studies that have identified key brain regions and modulatory mechanisms underlying placebo effects using well-established behavioral paradigms. Finally, we present a synthesis of recent genetics studies on the placebo effect, highlighting a promising link between genetic variants in the dopamine, opioid, serotonin, and endocannabinoid pathways and placebo responsiveness. Greater understanding of the behavioral, neurobiological, and genetic influences on the placebo effect is critical for evaluating medical interventions and may allow health professionals to tailor and personalize interventions in order to maximize treatment outcomes in clinical settings.

Genetics and the placebo effect: the placebome

Placebos are indispensable controls in randomized clinical trials (RCTs), and placebo responses significantly contribute to routine clinical outcomes. Recent neurophysiological studies reveal neurotransmitter pathways that mediate placebo effects. Evidence that genetic variations in these pathways can modify placebo effects raises the possibility of using genetic screening to identify placebo responders and thereby increase RCT efficacy and improve therapeutic care. Furthermore, the possibility of interaction between placebo and drug molecular pathways warrants consideration in RCT design. The study of genomic effects on placebo response, 'the placebome', is in its infancy. Here, we review evidence from placebo studies and RCTs to identify putative genes in the placebome, examine evidence for placebo-drug interactions, and discuss implications for RCTs and clinical care.

A study of promethazine hydrochloride and pentazocine intramuscular sedation along with 2 % lidocaine hydrochloride and adrenaline and comparison to placebo along with 2 % lidocaine hydrochloride and adrenaline for surgical extraction of mandibular third molar

BACKGROUND AND OBJECTIVES

The main objective is to study and compare the sedative and analgesic effects of intramuscular injection fortwin-phenergan along with local anesthetic and normal saline placebo along with local anesthetics in mandibular third molar surgery. We also assessed and compared the postoperative experience of the patient in relation to the pain intensity, time to first analgesic taken and total number of analgesics consumed over a period of 48 h in the two groups.

MATERIALS AND METHODS

Patients who came to the Department of Oral and Maxillofacial Surgery, The Regional Dental College; with complaints regarding mandibular third molar were chosen for the treatment. Patients were evaluated using Corah Dental Anxiety Scale (CDAS) and those patients having a score of CDAS 13 and above were selected. Sixty patients were selected out of which 30 patients formed group 1 and another 30 patients group 2. The patients were randomly divided with flip method into group 1 (study group) and or group 2 (controlled group).

RESULTS

Our study results showed that the operating conditions for both the groups at the end of surgery were similar without significant difference. Most of the surgical procedures were graded as excellent and good in both the groups except that difficulty was encountered in two patients from group 1 and one from group 2.

CONCLUSION

It could be concluded that particular drugs do not have much influence on the surgical procedure in our study, but it was found that patients from group 1 were more cooperative as compared to group 2 when difficulty was encountered during the surgical procedure.

Placebo and nocebo effects: a complex interplay between psychological factors and neurochemical networks

Placebo and nocebo effects have recently emerged as an interesting model to understand some of the intricate underpinnings of the mind-body interaction. A variety of psychological mechanisms, such as expectation, conditioning, anxiety modulation, and reward, have been identified, and a number of neurochemical networks have been characterized across different conditions, such as pain and motor disorders. What has emerged from the recent insights into the neurobiology of placebo and nocebo effects is that the psychosocial context around the patient and the therapy, which represents the ritual of the therapeutic act, may change the biochemistry and the neuronal circuitry of the patient's brain. Furthermore, the mechanisms activated by placebos and nocebos have been found to be the same as those activated by drugs, which suggests a cognitive/affective interference with drug action. Overall, these findings highlight the important role of therapeutic rituals in the overall therapeutic outcome, including hypnosis, which may have profound implications both in routine medical practice and in the clinical trials setting.

Placebo effects: from the neurobiological paradigm to translational implications

Today we are witnessing a new science of placebo, a complex discipline that encompasses several experimental approaches and translational implications. Modern neurobiological tools have been used to answer important questions in placebo research, such as the top-down modulation of sensory and motor systems as well as the influence of cognition, emotions, and learning on symptoms, diseases, and responses to treatments. What we have learned is that there is not one single placebo effect, but many. This review highlights the translational implications of this new knowledge, ranging from clinical trial design to medical practice to social and ethical issues.

Placebo use in pain management: The role of medical context, treatment efficacy, and deception in determining placebo acceptability

Placebo effects can act as powerful pain relievers. Although the ethics of therapeutic placebo use are highly controversial, recent evidence suggests that medical providers frequently utilize placebo treatments and patients may be open to these interventions in certain contexts. This investigation used a patient-centered approach to answer essential questions about placebo treatment acceptability. People with chronic musculoskeletal pain completed a placebo survey in which they rated their knowledge of placebo and its efficacy for alleviating pain, evaluated the acceptability of placebo analgesic interventions across several unique medical contexts, and responded to 6 different patient-physician treatment scenarios to assess the role of deception and placebo effectiveness on mood and provider trust. Results showed that participants had limited knowledge of placebo and its efficacy for alleviating pain. Placebo acceptability was highly dependent on the context of the intervention, as placebo treatments were considered acceptable when used as complementary/adjunct treatments and when no other established treatments were available. Also, an analgesic placebo response mitigated the negative consequences of deception by improving provider trust and decreasing negative mood. These findings suggest that, contrary to popular belief, patients may be rather pragmatic in their appraisals of placebo treatment acceptability, and may consider a variety of treatments/contexts as ethically permissible for managing their pain. This is the first study of its kind to quantify perceptions of placebo analgesia knowledge and efficacy among individuals with chronic pain, and to assess the role of different medical contexts in treatment acceptability.

Pain and the context

Pain is a sensory and emotional experience that is substantially modulated by psychological, social and contextual factors. Research now indicates that the influence of these factors is even more powerful than expected and involves the therapeutic response to analgesic drugs as well as the pain experience itself, which in some circumstances can even be a form of reward. Different experimental approaches and models, both in the laboratory and in the clinical setting, have been used to better characterize and understand the complex neurobiology of pain modulation. These approaches include placebo analgesia, nocebo hyperalgesia, hidden administration of analgesics, and the manipulation of the pain-reward relationship. Overall, these studies show that different neurochemical systems are activated in different positive and negative contexts. Moreover, pain can activate reward mechanisms when experienced within contexts that have special positive meaning. Because routine medical practice usually takes place in contexts that use different rituals, these neurobiological insights might have profound clinical implications.

Placebo and the new physiology of the doctor-patient relationship

Modern medicine has progressed in parallel with the advancement of biochemistry, anatomy, and physiology. By using the tools of modern medicine, the physician today can treat and prevent a number of diseases through pharmacology, genetics, and physical interventions. Besides this materia medica, the patient's mind, cognitions, and emotions play a central part as well in any therapeutic outcome, as investigated by disciplines such as psychoneuroendocrinoimmunology. This review describes recent findings that give scientific evidence to the old tenet that patients must be both cured and cared for. In fact, we are today in a good position to investigate complex psychological factors, like placebo effects and the doctor-patient relationship, by using a physiological and neuroscientific approach. These intricate psychological factors can be approached through biochemistry, anatomy, and physiology, thus eliminating the old dichotomy between biology and psychology. This is both a biomedical and a philosophical enterprise that is changing the way we approach and interpret medicine and human biology. In the first case, curing the disease only is not sufficient, and care of the patient is of tantamount importance. In the second case, the philosophical debate about the mind-body interaction can find some important answers in the study of placebo effects. Therefore, maybe paradoxically, the placebo effect and the doctor-patient relationship can be approached by using the same biochemical, cellular and physiological tools of the materia medica, which represents an epochal transition from general concepts such as suggestibility and power of mind to a true physiology of the doctor-patient interaction.

Analgesic placebo treatment perceptions: acceptability, efficacy, and knowledge

Current evidence supports the efficacy of placebo analgesia and illustrates that patients may be open to placebo use despite uncertainty regarding its mechanisms. Debate persists, however, concerning the ethics of placebo treatments. The purpose of the present web-based study was to expand upon the empirical literature on placebo analgesia ethics and acceptability. Participants (n = 100) provided their definition of a placebo and responded to 24 questions addressing placebo analgesia perceived knowledge, acceptability, effectiveness, and likelihood of placebo use among different health care providers. Results support previous research on the effects of placebo on negative mood and health care provider attributions, with findings illustrating that negative consequences of administration were largely mitigated by a beneficial treatment outcome. Results showed that participants conceptualized placebo as predominately inert and were mixed regarding interpretations of placebo effectiveness. Though acceptability ratings were dependent on the context of placebo administration, participants endorsing even moderate placebo acceptability were more open to placebo interventions and reported overall more positive treatment outcomes. Participants believed that placebos were used differentially among health care providers. Additional studies are needed to determine if placebo education can beneficially impact perceptions of placebo analgesia knowledge, acceptability, and treatment effectiveness.

PERSPECTIVE

This study presents an examination of analgesic placebo treatment perceived acceptability, efficacy, and knowledge among lay individuals. Our findings highlight the importance of assessing placebo conceptualizations and treatment perceptions in evaluating placebo ethics-a highly relevant finding that informs the clinical use of placebo components in managing pain.

Placebo-induced analgesia in an operant pain model in rats

Analgesia is particularly susceptible to placebo responses. Recent studies in humans have provided important insights into the neurobiology underlying placebo-induced analgesia. However, human studies provide incomplete mechanistic explanations of placebo analgesia because of limited capacity to use cellular, molecular, and genetic manipulations. To address this shortcoming, this article describes the development of a rat model of conditioned analgesia in an operant pain assay. Specifically, rats were conditioned to associate a placebo manipulation with the analgesic effect of 1mg/kg morphine (subcutaneously) on facial thermal pain. We found that conditioned (placebo) responding bore 3 of the hallmarks of placebo-induced analgesia: (1) strong interanimal variability in the response, (2) suppression by the opiate antagonist naloxone (5mg/kg subcutaneously), and (3) a positive predictive relationship between the unconditioned analgesic effect and the conditioned (placebo) effect. Because of the operant nature of the assay and the use of only a mild noxious thermal stimulus, we suggest that these results provide evidence of placebo-induced analgesia in a preclinical model that utilizes an affective behavioral end point. This finding may provide opportunities for invasive preclinical studies allowing greater understanding of placebo-induced analgesia, thus paving the way for avenues to harness its benefits.

Novel study designs to investigate the placebo response

Background

Investigating the size and mechanisms of the placebo response in clinical trials have relied on experimental procedures that simulate the double-blind randomized placebo-controlled design. However, as the conventional design is thought to elucidate drug rather than placebo actions, different methodological procedures are needed for the placebo response.

Methods

We reviewed the respective literature for trials designs that may be used to elucidate the size of the placebo response and the mechanisms associated with it.

Results

In general, this can be done by either manipulation the information provided to the subjects, or by manipulation the timing of the drug applied. Two examples of each strategy are discussed: the "balanced placebo design" (BDP) and the "balanced cross-over design" (BCD) and their variants are based on false information, while the "hidden treatment" (HT) and the ""delayed response test" (DRT) are based on manipulating the time of drug action. Since most such approaches include deception or incomplete information of the subjects they are suitable for patient only with authorized deception.

Conclusion

Both manipulating the information provided to subjects (BDP, DCD) or manipulating the timing of drug application (HT, DRT) allows overcoming some of the restrictions of conventional drug trials in the assessment of the placebo response, but they are feasible mostly in healthy subjects for ethical reasons.

How placebos change the patient's brain

Although placebos have long been considered a nuisance in clinical research, today they represent an active and productive field of research and, because of the involvement of many mechanisms, the study of the placebo effect can actually be viewed as a melting pot of concepts and ideas for neuroscience. Indeed, there exists not a single but many placebo effects, with different mechanisms and in different systems, medical conditions, and therapeutic interventions. For example, brain mechanisms of expectation, anxiety, and reward are all involved, as well as a variety of learning phenomena, such as Pavlovian conditioning, cognitive, and social learning. There is also some experimental evidence of different genetic variants in placebo responsiveness. The most productive models to better understand the neurobiology of the placebo effect are pain and Parkinson's disease. In these medical conditions, the neural networks that are involved have been identified: that is, the opioidergic-cholecystokinergic-dopaminergic modulatory network in pain and part of the basal ganglia circuitry in Parkinson's disease. Important clinical implications emerge from these recent advances in placebo research. First, as the placebo effect is basically a psychosocial context effect, these data indicate that different social stimuli, such as words and rituals of the therapeutic act, may change the chemistry and circuitry of the patient's brain. Second, the mechanisms that are activated by placebos are the same as those activated by drugs, which suggests a cognitive/affective interference with drug action. Third, if prefrontal functioning is impaired, placebo responses are reduced or totally lacking, as occurs in dementia of the Alzheimer's type.

All in the mind? Pain, placebo effect, and ergogenic effect of caffeine in sports performance

The ergogenic effects of caffeine on performance are well documented. These effects are more evident in endurance and short-duration, sustained-effort events than in interactive or stop-go sports. Experimentally-induced placebo effects of caffeine on sports performance have also been observed in a number of recent studies. In the present paper it is argued that, given the nature of the sports in which caffeine effects are observed, the well documented hypoalgesic effects of caffeine, and the fact that pain is highly placebo-responsive, a reduction in perceived pain might be the common factor in both the biologic and placebo ergogenic effects of caffeine on sports performance. This idea is supported by evidence from medicine that suggests placebo effects are often associated with mechanisms similar or identical to those of the substance the subject believes they have ingested. Research findings from both biomedicine and sports medicine that attest to the interaction of biologic and psychologic factors in caffeine and pain responses are briefly reviewed. In conclusion, it is recommended that researchers investigate the pain hypothesis. Furthermore, researchers should consider psychosocial factors that might modulate the pain response as variables of interest in future caffeine and performance research.

Acupuncture, psyche and the placebo response

With growing use of acupuncture treatment in various clinical conditions, the question has been posed whether the reported effects reflect specific mechanisms of acupuncture or whether they represent placebo responses, as they often are similar in effect size and resemble similarities to placebo analgesia and its mechanisms. We reviewed the available literature for different placebos (sham procedures) used to control the acupuncture effects, for moderators and potential biases in respective clinical trials, and for central and peripheral mechanisms involved that would allow differentiation of placebo effects from acupuncture and sham acupuncture effects. While the evidence is still limited, it seems that biological differences exist between a placebo response, e.g. in placebo analgesia, and analgesic response during acupunture that does not occur with sham acupuncture. It seems advisable that clinical trials should include potential biomarkers of acupuncture, e.g. measures of the autonomic nervous system function to verify that acupuncture and sham acupuncture are different despite similar clinical effects.

Placebo effect of an inert gel on experimentally induced leg muscle pain

Purpose

This study examined the therapeutic effects of an inert placebo gel on experimentally induced muscle pain in a sports therapy setting. It aimed to investigate the degree to which conditioned analgesia, coupled with an expectation of intervention, was a factor in subsequent analgesia.

Methods

Participants were sixteen male and eight female sports therapy students at a UK University. With institutional ethics board approval and following informed consent procedures, each was exposed to pain stimulus in the lower leg in five conditions, ie, conditioning, prebaseline, experimental (two placebo gel applications), and postbaseline. In conditioning trials, participants identified a level of pain stimulus equivalent to a perceived pain rating of 6/10. An inert placebo gel was then applied to the site with the explicit instruction that it was an analgesic. Participants were re-exposed to the pain stimulus, the level of which, without their knowledge, had been decreased, creating the impression of an analgesic effect resulting from the gel. In experimental conditions, the placebo gel was applied and the level of pain stimulus required to elicit a pain rating of 6/10 recorded.

Results

Following application of the placebo gel, the level of pain stimulus required to elicit a pain rating of 6/10 increased by 8.2%. Application of the placebo gel significantly decreased participant’s perceptions of muscle pain (P = 0.001).

Conclusion

Subjects’ experience and expectation of pain reduction may be major factors in the therapeutic process. These factors should be considered in the sports therapeutic environment.

Progress in genetic studies of pain and analgesia

Interindividual variability in pain sensitivity and the response to analgesic manipulations remains a considerable clinical challenge as well as an area of intense scientific investigation. Techniques in this field have matured rapidly so that much relevant data have emerged only in the past few years. Our increasing understanding of the genetic mediation of these biological phenomena have nonetheless revealed their surprising complexity. This review provides a comprehensive picture and critical analysis of the field and its prospects.