Medication-enhanced behavior therapy for alcohol use disorder: Naltrexone, Alcoholics Anonymous Facilitation, and OPRM1 genetic variation

Tryptophan and Substance Abuse: Mechanisms and Impact

Addiction, the continuous misuse of addictive material, causes long-term dysfunction in the neurological system. It substantially affects the control strength of reward, memory, and motivation. Addictive substances (alcohol, marijuana, caffeine, heroin, methamphetamine (METH), and nicotine) are highly active central nervous stimulants. Addiction leads to severe health issues, including cardiovascular diseases, serious infections, and pulmonary/dental diseases. Drug dependence may result in unfavorable cognitive impairments that can continue during abstinence and negatively influence recovery performance. Although addiction is a critical global health challenge with numerous consequences and complications, currently, there are no efficient options for treating drug addiction, particularly METH. Currently, novel treatment approaches such as psychological contingency management, cognitive behavioral therapy, and motivational enhancement strategies are of great interest. Herein, we evaluate the devastating impacts of different addictive substances/drugs on users' mental health and the role of tryptophan in alleviating unfavorable side effects. The tryptophan metabolites in the mammalian brain and their potential to treat compulsive abuse of addictive substances are investigated by assessing the functional effects of addictive substances on tryptophan. Future perspectives on developing promising modalities to treat addiction and the role of tryptophan and its metabolites to alleviate drug dependency are discussed.

Midazolam, methamphetamine, morphine and nicotine intake in high‐drinking‐in‐the‐dark mice

The high-drinking-in-the-dark (HDID) lines of mice were selectively bred for achieving high blood alcohol levels in the drinking-in-the-dark (DID) task and have served as a unique genetic risk model for binge-like alcohol intake. However, little is known about their willingness to consume other addictive drugs. Here, we examined (a) whether the HDID-1 and HDID-2 lines of mice would voluntarily consume midazolam, methamphetamine, morphine and nicotine in a DID test and (b) whether the HDID lines differ from their founders, heterogeneous stock/Northport (HS/NPT), in consumption levels of these drugs at the concentrations tested. Separate groups of HDID-1, HDID-2 and HS/NPT mice were given 4 days of access to each drug, using the single-bottle, limited-access DID paradigm. Male and female mice of both HDID lines consumed all four offered drugs. We observed no genotype differences in 40 μg/ml methamphetamine intake, but significant differences in nicotine, midazolam and morphine intake. Both HDID lines drank significantly more (150 μg/ml) midazolam than their founders, providing strong support for a shared genetic contribution to binge ethanol and midazolam intake. HDID-2 mice, but not HDID-1 mice, consumed more morphine (700 μg/ml) and more nicotine across a range of concentrations than HS/NPT mice. These results demonstrate that the HDID mice can be utilized for tests of voluntary drug consumption other than ethanol and highlight potentially important differences between HDID lines in risk for elevated drug intake.

Exploring the Role of Alcohol Metabolizing Genotypes in a 12-Week Clinical Trial of Naltrexone for Alcohol Use Disorder

Background: The efficacy of naltrexone in the treatment of alcohol use disorder (AUD) has been associated with a set of variables not directly related with the expression of opioid receptors. All the variables have been found to be highly associated with AUD itself or more severe clinical levels of AUD. Objectives: Given the high association between alcohol metabolizing enzymes (AME) and the outcome of AUD, the present study aims to investigate the role of AME genotype variants in the treatment of AUD with naltrexone. Methods: We carried out a 12-week longitudinal clinical trial based on the treatment of AUD patients with naltrexone (N = 101), stratified by different alcohol metabolization genotypes. Genotyping was performed after the inclusion of the patients in the study, based on the individual presence of single nucleotide polymorphisms (SNPs) in the ADH (alcohol dehydrogenase)1B (ADH1B*2 and ADH1B*3), ADH1C (ADHC*1) and ALDH (aldehyde dehydrogenase) 2 (ALDH2*2) genes. The outcome of alcohol use has been monitored employing the timeline follow-back during the treatment. Results: The ADH1C*1 (Ile350Val, rs698) and ALDH2*2 (Glu504Lys, rs671) polymorphisms were associated with a better response to naltrexone treatment, whereas the ADH1B*3 (Arg370Cys, rs2066702) allelic variant showed a negative outcome. Conclusions: The present study explores a genomic setting for the treatment of AUD with naltrexone. According to our findings, the association between ADH1C*1 and ALDH2*2 variants and better outcomes suggests a successful treatment, whereas the ADH1B*3 mutated allele might lead to an unsuccessful treatment. Further studies should be performed to investigate the relationship between alcohol metabolizing genotypes, the family history of alcohol use disorders and the effect of naltrexone on the outcomes. Genotyping may be a valuable tool for precision-medicine and individualized approach, especially in the context of alcohol use disorders. The small number of subjects was the main limitation of the present study.