Retrospectively assessed subjective effects of initial opioid use differ between opioid misusers with opioid use disorder (OUD) and those who never progressed to OUD: Data from a pilot and a replication sample

Polymorphisms in the A118G SNP of the OPRM1 gene produce different experiences of opioids: A human laboratory phenotype-genotype assessment

Allelic variations in the A118G SNP of the OPRM1 gene change opioid signaling; however, evaluations of how allelic differences may influence opioid effects are lacking. This human laboratory paradigm examined whether the AA versus AG/GG genotypes determined opioid response profiles. Individuals with limited opioid exposure (N = 100) completed a five-day within-subject, double-blind, placebo-controlled, residential study. Participants were admitted (Day 1), received 4 mg hydromorphone (Day 2) and 0 mg, 2 mg and 8 mg hydromorphone in randomized order (Days 3-5) and completed self-reported visual analog scale (VAS) ratings and Likert scales, observed VAS, and physiological responses at baseline and for 6.5 h post-dose. Outcomes were analysed as peak/nadir effects over time as a function of genotype (available for N = 96 individuals; AG/GG = 13.5%, AA = 86.4%). Participants with AG/GG rated low and moderate doses of hydromorphone as significantly more positive (e.g., Good Effects VAS, coasting, drive, friendly, talkative, stimulation) with fewer negative effects (e.g., itchy skin, nausea, sleepiness), and were also observed as being more talkative and energetic relative to persons with AA. Persons with AG/GG were less physiologically reactive as determined by diastolic blood pressure and heart rate, but had more changes in core temperature compared with those with AA. Persons with AA also demonstrated more prototypic agonist effects across doses; persons with AG/GG showed limited response to 2 mg and 4 mg. Data suggest persons with AG/GG genotype experienced more pleasant and fewer unpleasant responses to hydromorphone relative to persons with AA. Future studies should replicate these laboratory findings in clinical populations to support a precision medicine approach to opioid prescribing.

Can initial experiences with drugs predict future drug abuse risks?

Initial experiences with drugs may influence an individual's motivations for continued use. This study evaluated the relationship between subjective effects elicited by an individual's first use of alcohol or cannabis, Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition (DSM-5) alcohol use disorder (AUD) or cannabis use disorder (CUD) severity, and behavioral economic demand for alcohol or cannabis. Self-reports of initial subjective effects associated with drugs were analyzed for N = 463 participants whose first substance use was either alcohol or cannabis. The likelihood that a particular subjective effect at the time of first use was associated with current AUD/CUD was assessed using ordinal logistic regression with subjective effects as predictors of DSM-5 severity. Behavioral economic demand was assessed using a hypothetical purchase task in which participants indicated their hypothetical consumption of alcohol or cannabis as a function of price. Significant associations were observed for initial subjective effects elicited by alcohol or cannabis and increased DSM-5 severity: (alcohol) relief (OR = 2.52 [95% CI 1.51-4.25], p = .0005) and (cannabis) energetic (OR = 2.31 [95% CI 3.27-55.5], p = .0004). The mean (± SEM) P_max value for the alcohol subgroup endorsing relief ($96.22 ± $26.48) was significantly greater than the P_max value for the alcohol subgroup not endorsing relief ($33.81 ± $12.93), t(237) = 2.276, p = .0237. These results suggest that the initial subjective effects associated with a given substance may predict the development and/or severity of substance misuse and substance use disorders (SUDs). These findings are consistent with anecdotal reports that persons with SUD feel energized by the use of substances whereas persons without SUD do not report experiencing such subjective effects upon first use. (PsycInfo Database Record (c) 2023 APA, all rights reserved).

Can the Type of Subjective Response to First Opioid Exposure Predict the Risk of Opioid Use Disorder? A Scoping Review

BACKGROUND

Effective identification of individuals at increased risk for developing opioid use disorder (OUD) could reduce the overdose fatalities and mitigate the harm of the opioid epidemic. Early evidence has linked certain subjective experiences during the first substance exposure to subsequent substance misuse. This is consistent with anecdotal evidence that "first response" to opioids may distinguish those who later develop OUD from those who do not, further suggesting individual differences in neural activity and responses to specific substances.

OBJECTIVE

The objective of this scoping review was to evaluate the evidence on the relationship between the subjective first response to opioids and the risk of developing OUD.

METHODS

Ovid MEDLINE search (through 1/29/2021), followed by the search for articles published by the first/senior authors (PubMed) and references citing (Web of Science Citing Reference) identified eligible publications, was focused on studies involving humans, published in English, and describing the initial subjective response to opioid exposure and its association with OUD development or its risk. Systematic data extraction was completed for each eligible study.

RESULTS

3,364 title/abstracts and 48 full-text articles were reviewed. Four articles, describing six studies (526 adult participants) were eligible and included. These studies were methodologically heterogeneous, including 2 randomized controlled trials, and 1 case-control, and 3 cross-sectional studies, with small sample sizes, precluding data pooling and meta-analysis. Results suggested that individuals with OUD or at elevated risk for OUD (determined by the validated OUD risk assessment surveys) were more likely to report their "first opioid response" as euphoric compared to their counterparts.

CONCLUSIONS

Limited evidence suggests that subjectively-reported euphoric response to first opioid exposure could predict the OUD risk. Prospective studies are needed to evaluate the utility of assessing first response (e.g., via brief point-of-care screening surveys) for informing clinical decisions when prescribing opioids.

Dopamine Supersensitivity: A Novel Hypothesis of Opioid-Induced Neurobiological Mechanisms Underlying Opioid-Stimulant Co-use and Opioid Relapse

Emergent harms presented by the co-use of opioids and methamphetamine highlight the broader public health challenge of preventing and treating opioid and stimulant co-use. Development of effective therapeutics requires an understanding of the physiological mechanisms that may be driving co-use patterns, specifically the underlying neurobiology of co-use and how they may facilitate (or be leveraged to prevent) continued use patterns. This narrative review summarizes largely preclinical data that demonstrate clinically-meaningful relationships between the dopamine and opioid systems with direct implications for opioid and stimulant co-use. Synthesized conclusions of this body of research include evidence that changes in the dopamine system occur only once physical dependence to opioids develops, that the chronicity of opioid exposure is associated with the severity of changes, and that withdrawal leaves the organism in a state of substantive dopamine deficit that persists long after the somatic or observed signs of opioid withdrawal appear to have resolved. Evidence also suggests that dopamine supersensitivity develops soon after opioid abstinence and results in increased response to dopamine agonists that increases in magnitude as the abstinence period continues and is evident several weeks into protracted withdrawal. Mechanistically, this supersensitivity appears to be mediated by changes in the sensitivity, not quantity, of dopamine D2 receptors. Here we propose a neural circuit mechanism unique to withdrawal from opioid use with implications for increased stimulant sensitivity in previously stimulant-naïve or inexperienced populations. These hypothesized effects collectively delineate a mechanism by which stimulants would be uniquely reinforcing to persons with opioid physical dependence, would contribute to the acute opioid withdrawal syndrome, and could manifest subjectively as craving and/or motivation to use that could prompt opioid relapse during acute and protracted withdrawal. Preclinical research is needed to directly test these hypothesized mechanisms. Human laboratory and clinical trial research is needed to explore these clinical predictions and to advance the goal of developing treatments for opioid-stimulant co-use and/or opioid relapse prevention and withdrawal remediation.

Early Life Stress and Risks for Opioid Misuse: Review of Data Supporting Neurobiological Underpinnings

A robust body of research has shown that traumatic experiences occurring during critical developmental periods of childhood when neuronal plasticity is high increase risks for a spectrum of physical and mental health problems in adulthood, including substance use disorders. However, until recently, relatively few studies had specifically examined the relationships between early life stress (ELS) and opioid use disorder (OUD). Associations with opioid use initiation, injection drug use, overdose, and poor treatment outcome have now been demonstrated. In rodents, ELS has also been shown to increase the euphoric and decrease antinociceptive effects of opioids, but little is known about these processes in humans or about the neurobiological mechanisms that may underlie these relationships. This review aims to establish a theoretical model that highlights the mechanisms by which ELS may alter opioid sensitivity, thereby contributing to future risks for OUD. Alterations induced by ELS in mesocorticolimbic brain circuits, and endogenous opioid and dopamine neurotransmitter systems are described. The limited but provocative evidence linking these alterations with opioid sensitivity and risks for OUD is presented. Overall, the findings suggest that better understanding of these mechanisms holds promise for reducing vulnerability, improving prevention strategies, and prescribing guidelines for high-risk individuals.