The Role of Endogenous Beta-Endorphin and Enkephalins in the Crosstalk Between Ethanol and Morphine

Background: There is clinical concern about the combined use of alcohol and opiates. Several lines of evidence support an interaction between alcohol and the endogenous opioid system. Thus, we hypothesized that ethanol, by causing the release of opioid peptides, may sensitize the system to the action of exogenous opioids such as morphine. Objectives: In this study, using the place conditioning paradigm, a model of reward, we determined whether a morphine challenge would alter the pre-established preference induced by ethanol conditioning in mice, and whether this response was mediated by the mu opioid receptor (MOP). Given that ethanol exposure stimulates the release of opioid peptides, we also assessed the role of beta-endorphin (β-END) and enkephalins (ENKs) in this response. Methods: Mice lacking MOPs, β-END, and/or ENKs, and their respective wild-type controls were tested for preconditioning place preference on day 1. Mice were then conditioned with ethanol (2 g/kg) versus saline on days 2 to 4 and then tested under a drug-free state for postconditioning place preference on day 5. On day 8, mice received a single injection of morphine (5 mg/kg) and were tested for place preference. On the test days, mice were placed in the central chamber and allowed to explore the chambers. The amount of time that mice spent in the drug-paired chamber was recorded. Results: We found that a challenge dose of morphine given on day 8 enhanced the conditioned place preference (CPP) response in mice previously conditioned with ethanol. This response was abolished in MOP-null mice, confirming the role of MOPs in this response. Although this enhanced response was not altered in mice lacking either β-END or ENKs compared to their wild-type littermates/controls, it was completely blunted in mice lacking both β-END and enkephalins. Conclusions: Together, these results suggest that these opioid peptides jointly mediate the crosstalk between the rewarding actions of morphine and ethanol.

Community alcohol sales and opioid poisoning deaths: Alcohol serving space as a harm reduction opportunity

The concurrent use of opioids and alcohol is particularly dangerous for individuals. Alcohol is commonly seen in opioid overdose death toxicology reports and, concurrent use of alcohol and opioids is often reported by individuals across a diverse range of opioid use profiles. This study investigates whether there is a community-level relationship between alcohol sales and opioid-related overdose deaths to inform the situating of harm reduction efforts in spaces most likely to reduce substance-related harms. Using an ecological design, zip code-level data for New Hampshire were combined from the US Census Bureau's American Community Survey (sociodemographics), the National Alcohol Beverage Control Association (alcohol retail sales), and the NH Office of the Chief Medical Examiner (zip code level opioid poisoning deaths) to investigate the relationship between alcohol sales and opioid-related poisoning deaths at a community level in a state with the third highest rate of opioid poisoning deaths for the year the current study represents. Using a spatial error regression model approach, opioid-related poisoning deaths were higher in zip codes with greater population density and on-premise alcohol sales and were lower in zip codes with greater off-premise alcohol sales and area disadvantage. The findings here co-locate higher levels of on-premise alcohol sales and opioid-related poisoning deaths at a community-level, mirroring individual-level findings on the danger of mixing these two substances. Results inform harm reduction approaches by identifying substance use spaces where overdose prevention messaging or policy change may be most effective.

A descriptive coronial study of heroin toxicity deaths in Australia, 2020-2022: Characteristics, toxicology and survival times

BACKGROUND AND AIMS

Mortality rates among people who use heroin are estimated to be 15 times that of the general population. The study aimed to determine (1) the case characteristics and circumstances of death of heroin-related toxicity deaths in Australia, 2020-2022; (2) their toxicological profile and major autopsy findings; (3) the proportion of cases in which blood 6-acetyl morphine (6AM) was detected, as a proxy measure of survival times; and (4) compare 6AM positive and negative cases on toxicology, circumstances of death and acute clinical presentation.

DESIGN

Retrospective study of heroin toxicity deaths in Australia, 2020-2022, retrieved from the National Coronial Information System.

SETTING

This study was conducted Australia-wide.

CASES

There were 610 cases of fatal heroin-related drug toxicity.

MEASUREMENTS

Information was collected on characteristics, manner of death, toxicology and autopsy results.

FINDINGS

The mean age was 42.6 years (range 18-73 years), 80.5% were male and 7.5% were enrolled in a drug treatment programme. The circumstances of death were as follows: unintentional drug toxicity (86.2%), combined unintentional drug toxicity/disease (11.3%) and intentional drug toxicity (2.5%). The median free morphine concentration was 0.17 mg/L (range 0.00-4.20 mg/L). Psychoactive drugs other than heroin were present in 95.2% (Confidence Interval 93.1%-96.8%), most commonly hypnosedatives (62.3%, 58.2%-66.4%) and psychostimulants (44.8%, 40.7%-49.1%). Major autopsy findings of clinical significance included acute bronchopneumonia (14.8%, 11.3%-18.8%), emphysema (16.9%, 13.2%-21.1%), cardiomegaly (30.1%, 12.7%-28.2%), coronary artery disease (27.4%, 23.0%-32.3%), coronary replacement fibrosis (13.4%, 10.1%-17.3%), hepatic cirrhosis (8.8%, 6.6%-12.2%) and renal fibrosis (10.3%, 7.3%-14.0%). In 47.0% (42.3%-51.2%), 6AM was present in blood.

CONCLUSIONS

The 'typical' heroin overdose case in Australia from 2020 to 2022 was a male who injected heroin, aged in the 40s, not enrolled in a treatment programme and had used multiple drugs. In over half of cases, there had been a sufficient survival time for 6-acetyl morphine to have been metabolised, which may indicate times in excess of 20-30 min.