Cognitive Impairment and Tramadol Dependence

A comparative study of the efficacy of venlafaxine and naltrexone for relapse prevention in patients with opioid use disorder attributed to tramadol

Tramadol and venlafaxine share similar pharmacological characteristics that may allow for overlapping therapeutic indications for them. The objective of this study was to compare the efficacy of venlafaxine and naltrexone in the treatment of tramadol abuse. This comparative trial included 95 patients with tramadol abuse who were detoxified for 2 weeks. Twenty-eight participants underwent the maintenance phase, while the remaining participants (n = 67) dropped out. The patients were randomized to use 50 mg/day of naltrexone or 225 mg/day of venlafaxine for 8 weeks. All participants were interviewed using SCID-I (DSM-IV-TR) criteria for diagnosing substance use and other psychiatric disorders. The proportion of relapsed patients was comparable between the naltrexone and venlafaxine groups (29.4% vs. 30.4%, P  = 0.9). However, participants in the venlafaxine group stayed in treatment longer than participants in the naltrexone group, and the difference was significant (22.9 ± 7.89 days vs. 16.9 ± 3.4 days, P = 0.01). Only psychiatric comorbidity was found to be significantly associated with retention in treatment (80% vs. 22%, P  = 0.005). Venlafaxine is as effective as naltrexone in preventing relapse in patients with tramadol abuse. Venlafaxine was more effective than naltrexone in treatment retention.

Gender disparities in neuropsychological assessment research in drug abuse populations: A systematic review

Objective: To systematically review the literature on the neurocognitive effects of drug use to determine if there are significant gender differences. Methods: In April 2023, we conducted a broad search in MEDLINE (via PubMed), PsycINFO, and Embase for original research studies that used objective neuropsychological assessment to evaluate neurocognition in persons with drug use. Data extraction was performed in a masked, duplicate fashion. Results: Our initial search returned 22,430 records, of which 273 articles were included in our analysis. We found significant underrepresentation of women as participants in the studies. Twenty-one percent of studies had exclusively male participants; when women were included, they averaged only 23% of the sample. Only 49 studies sufficiently documented an analysis of their results by gender; due to the heterogeneity in study characteristics, no conclusions about cognitive differences between women and men could be made. Conclusions: Women are significantly underrepresented in the research on cognition in drug use. Increased efforts to include more women participants and consistent analysis and reporting of data for potential gender differences will be required to close this gap in knowledge, which may lead to improved substance abuse treatment approaches for women.

Exploring the potential use of melatonin as a modulator of tramadol-induced rewarding effects in rats

Background

Melatonin is responsible for regulating the sleep-wake cycle and circadian rhythms in mammals. Tramadol, a synthetic opioid analgesic, is used to manage moderate to severe pain but has a high potential for abuse and dependence. Studies have shown that melatonin could be a potential modulator to reduce tramadol addiction.

Methods

Male Wistar rats were used to investigate the effect of melatonin on tramadol-induced place preference. The rats were divided into four groups: control, tramadol, tramadol + melatonin (single dose), and tramadol + melatonin (repeated doses). Tramadol was administered intraperitoneally at 40 mg/kg, while melatonin was administered at 50 mg/kg for both the single dose and repeated-dose groups. The study consisted of two phases: habituation and acquisition.

Results

Tramadol administration produced conditioned place preference (CPP) in rats, indicating rewarding effects. However, melatonin administration blocked tramadol-induced CPP. Surprisingly, repeated doses of melatonin were ineffective and did not reduce the expression of CPP compared to that of the single dose administration.

Conclusion

The study suggests that melatonin may be a potential therapeutic option for treating tramadol addiction. The results indicate that melatonin attenuates the expression of tramadol-induced CPP, supporting its uses as an adjunct therapy for managing tramadol addiction. However, further studies are needed to investigate its effectiveness in humans.

The toxic profile of tramadol combined with nicotine on the liver and testicles: evidence from endoplasmic reticulum stress

BACKGROUND

Tramadol is one of the most commonly abused substances in the Middle East. Furthermore, smoking is extremely common among the population.

METHODS

An experimental study was performed on Sprague-Dawley rats to explore the effects of both nicotine and tramadol on the liver and testes. The tramadol was administered at 10 and 20 mg/kg, respectively, while the nicotine was administered at 125 mg/kg. Histological examination and androgen receptor ELISA assay showed mild effects on the liver and proofed safety on the testis. Western blot analysis of BIP (immunoglobulin heavy-chain binding protein) and CHOP (CCAAT-enhancer-binding protein homologous protein) revealed that fewer problems were induced by adding nicotine to tramadol. Autophagy marker LCIII and apoptosis marker caspase-8 showed similar effects to CHOP and BIP on liver samples. The real-time PCR of BIP expression showed similar but not identical results.

CONCLUSIONS

The results showed mild endoplasmic reticulum stress, autophagy, and apoptosis in the liver samples. Histological examination revealed stable spermatogenesis with average androgen receptor blood levels in the different groups.

Side effects based network construction and drug repositioning of ropinirole as a potential molecule for Alzheimer's disease: an in-silico, in-vitro, and in-vivo study

Alzheimer's disease (AD) is the leading cause of dementia in older adults. Drug repositioning is a process of finding new therapeutic applications for existing drugs. One of the methods in drug repositioning is to use the side-effect profile of a drug to identify a new therapeutic indication. The drugs with similar side-effects may act on similar biological targets and could affect the same biochemical process. In this study, we explored the Food and Drug Administration-approved drugs using PROMISCUOUS database to find those that have adverse effects profile comparable with the ligands being studied or used to treat AD. Here, we found that the ropinirole, a dopamine receptor agonist, shared a maximum number of side-effects with the drugs proven beneficial for treating AD. Furthermore, molecular modelling demonstrated that ropinirole exhibited strong binding affinity (-9.313 kcal/mol) and best ligand efficiency (0.49) with sigma-1 receptor. Here, we observed that the quaternary amino group of ropinirole is essential for binding with sigma-1 receptor. Molecular dynamic simulation indicated that the movement of the carboxy-terminal helices (α4/α5) could play a major role in the receptor's physiological functions. The neurotoxicity induced by Aβ25-35 in SH-SY5Y cells was reduced by ropinirole at concentrations 10, 30, and 50 µM. The effect on spatial learning and memory was examined in mice with Aβ25-35 induced memory deficit using the radial arm maze. Ropinirole (10 and 20 mg/kg) significantly improved the short and long-term memories in the radial arm maze test. Our results suggest that ropinirole has the potential to be repositioned for AD treatment.Communicated by Ramaswamy H. Sarma.

Self-perceived care needs and quality of life in people with cognitive impairment during routine care at home: cross-sectional results of the interventional study

BACKGROUND

Cognitive impairment (CI) is one of the most common disabling symptoms in the elderly, and people with CI face a variety of unmet care needs. There is limited evidence on the relationship between unmet needs and quality of life (QoL) of people with CI. The aim of this study is to analyse the current situation of unmet needs and QoL among people with CI, and to explore the correlation between QoL and unmet needs.

METHODS

The analyses use baseline data of the intervention trial, which recruited 378 participants to complete the questionnaire including the Camberwell Assessment of Need for the Elderly (CANE), and the Medical Outcomes Study 36-item Short-Form (SF-36). The SF-36 was further gathered into physical component summary (PCS) and mental component summary (MCS). Multiple linear regression analysis was conducted to explore the correlations between unmet care needs and PCS and MCS of SF-36.

RESULTS

The mean score of each of the eight domains of SF-36 was significantly lower than the Chinese population norm. The incidence of unmet needs ranged from 0 to 65.1%. Multiple linear regression results showed that living in rural areas (Beta=-0.16, P < 0.001), having unmet physical needs (Beta=-0.35, P < 0.001), and unmet psychological needs (Beta=-0.24, P < 0.001) were associated with lower PCS scores, whereas duration of CI > 2 years (Beta=-0.21, P < 0.001), unmet environmental needs (Beta=-0.20, P < 0.001), and unmet psychological needs (Beta=-0.15, P < 0.001) were associated with lower MCS scores.

CONCLUSION

The main results support the important view that lower QoL scores are associated with unmet needs in people with CI, depending on the domain. Given that the more unmet needs can further worsen QoL, it is recommended that more strategies should be taken, especially for those with unmet care needs, so as to improve their QoL.

Tramadol and Codeine Stacking/Boosting Dose Exposure Induced Neurotoxic Behaviors, Oxidative Stress, Mitochondrial Dysfunction, and Neurotoxic Genes in Adolescent Mice

In spite of the increasing epidemic of pharmaceutical opioids (codeine and tramadol) misuse and abuse among the adolescents, little is known about the neurotoxic consequences of the widespread practice of tramadol and codeine abuse involving increasing multiple doses across days, referred to as stacking and boosting. Hence, in this study, we replicated stacking and boosting doses of tramadol, codeine alone, or in combination on spontaneous motor activity and cognitive function in adolescent mice and adduced a plausible mechanism of possible neurotoxicity. Ninety-six adolescent mice were randomly distributed into 4 groups (n = 24 per group) and treated thrice daily for 9 days with vehicle, tramadol (20, 40, or 80 mg/kg), codeine (40, 80, or 160 mg/kg), or their combinations. Exposure of mice to tramadol induced hyperactivity and stereotypic behavior while codeine exposure caused hypoactivity and nootropic effect but tramadol-codeine cocktail led to marked reduction in spontaneous motor activity and cognitive function. In addition, tramadol, codeine, and their cocktail caused marked induction of nitroso-oxidative stress and inhibition of mitochondrial complex I activity in the prefrontal cortex (PFC) and midbrain (MB). Real-time PCR expression profiling of genes encoding neurotoxicity (RT) showed that tramadol exposure upregulate 57 and downregulate 16 neurotoxic genes, codeine upregulate 45 and downregulate 25 neurotoxic genes while tramadol-codeine cocktail upregulate 52 and downregulate 20 neurotoxic genes in the PFC. Findings from this study demonstrate that the exposure of adolescents mice to multiple and increasing doses of tramadol, codeine, or their cocktail lead to spontaneous motor coordination deficits indicative of neurotoxicity through induction of oxidative stress, inhibition of mitochondrial complex I activity and upregulation of neurotoxicity encoding genes in mice.

Green Assessment of Chromatographic Methods Used for the Analysis of Four Methamphetamine Combinations with Commonly Abused Drugs

Numerous agents with anxiolytic or stimulant effects have the potential to be overused, and their misuse is associated with serious side effects. In Saudi Arabia, the estimated percentage of Saudis who abuse drugs is around 7–8% and the age range is 12–22 years. Methamphetamine, captagon, tramadol, heroin, and cannabis/cannabinoids have been proven to be the most commonly abused drugs in Saudi Arabia, with methamphetamine being at the top of the list. The present study focuses on the chromatographic analytical methods used for the analysis of methamphetamine in combination with commonly abused drugs, aiming to point out the greenest among them. These mixtures have been chosen as they are analyzed periodically and frequently in criminal evidence and forensic medicine. Therefore, the chances of hazards for analysts and the environment are high if the mixtures are not handled appropriately. This study aims to compare 23 chromatographic methods used for the analysis of methamphetamine mixtures in four major combinations, and to assess their greenness by using three greenness assessment tools, namely, NEMI, ESA and AGREE, to recommend the greenest analytical method. The NEMI results were proven to have low discriminating abilities and, accordingly, the comparisons are based on ESA and AGREE scores. The analysis results show that the safest methods with the most eco-friendly results (based on ESA and AGREE) are the GC-MS method proposed by Mohammed et al. to analyze methamphetamine and captagon mixtures (ESA = 79 and AGREE = 0.57), the UHPLC–MS-MS method proposed by Busardò et al. to analyze methamphetamine and cannabis/cannabinoid mixtures (ESA = 78 and AGREE = 0.57), the LC-MS method proposed by Herrin et al. to analyze methamphetamine and tramadol mixtures (ESA = 81 and AGREE = 0.56), and the LC-MS method proposed by Postigo-et al to analyze methamphetamine and heroin mixtures (ESA = 76 and AGREE = 0.58).

Does tramadol dependence impair cognitive functions?

The aim of this study is to assess the effect of tramadol use on cognitive functions, especially executive functions. Thirty tramadol use disorder patients were recruited from those admitted to the toxicology departments of Menoufia University Hospitals for detoxification. Thirty controls were recruited from employees working at the faculty of medicine, Menoufia University. Both patients and controls underwent a demographic sheet and computerized cognitive battery. Patients also completed another sheet about substance use history. Urine screening for drugs was performed on all patients prior to admission. No differences regarding age, education or marital status were found between patients and controls. Tramadol-dependent patients showed cognitive impairment in the form of impaired visual-spatial memory and executive functions in comparison to controls. After detoxification, patients showed improvement regarding executive functions but not visual-spatial memory. Tramadol impairs cognitive functions in tramadol-dependent patients.

Spectral Power Density analysis of the resting-state as a marker of the central effects of opioid use in fibromyalgia

Spectral power density (SPD) indexed by electroencephalogram (EEG) recordings has recently gained attention in elucidating neural mechanisms of chronic pain syndromes and medication use. We compared SPD variations between 15 fibromyalgia (FM) women in use of opioid in the last three months (73.33% used tramadol) with 32 non-users. EEG data were obtained with Eyes Open (EO) and Eyes Closed (EC) resting state. SPD peak amplitudes between EO-EC were smaller in opioid users in central theta, central beta, and parietal beta, and at parietal delta. However, these variations were positive for opioid users. Multivariate analyses of variance (ANOVAs) revealed that EO-EC variations in parietal delta were negatively correlated with the disability due to pain, and central and parietal beta activity variations were positively correlated with worse sleep quality. These clinical variables explained from 12.5 to 17.2% of SPD variance. In addition, central beta showed 67% sensitivity / 72% specificity and parietal beta showed 73% sensitivity/62% specificity in discriminating opioid users from non-users. These findings suggest oscillations in EEG might be a sensitive surrogate marker to screen FM opioid users and a promising tool to understand the effects of opioid use and how these effects relate to functional and sleep-related symptoms.

Prevalence, correlates, and consequences of attention-deficit/hyperactivity disorder in a clinical sample of adults with tramadol use in Egypt

BACKGROUND AND OBJECTIVES

Many studies investigated the association between attention-deficit/hyperactivity disorder (ADHD) and substance use disorders (SUDs) but none focused on the association between ADHD and nonmedical prescription opioids such as tramadol. The objective of this study was to assess the prevalence, correlates, and consequences of co-occurrence of ADHD and tramadol use among adults.

METHODS

This study included 122 Egyptian adults with opioid use disorders attributed to tramadol (N = 122). Participants were recruited from the psychiatric outpatient clinic and inpatient unit of Zagazig University Hospital, Egypt. ADHD and SUDs were assessed by using the Adult ADHD Self-Report Scale (ASRS-v 1.1) and SCID-I criteria of DSM-5, respectively. All participants were screened for drugs by urinalysis.

RESULTS

Forty percent of the participants used tramadol alone, whereas the remaining used it with other substances, such as alcohol (51.6%) and cannabis (48.4%). Thirty-eight cases (31%) had adult ADHD and most of them had inattentive or mixed types. Adults with tramadol use and ADHD were more likely to have a younger age of onset of tramadol use, use a higher dose of tramadol, and use it for a longer duration than those with tramadol use without ADHD.

CONCLUSIONS AND DISCUSSION

ADHD in adults with tramadol use is common and is associated with early-onset, high dose, and long duration of tramadol use.

SCIENTIFIC SIGNIFICANCE

This is the first study to investigate the co-occurrence of ADHD and tramadol misuse among adults.

Effects of chronic tramadol administration on cognitive flexibility in mice

RATIONALE

Tramadol is widely used for pain relief especially in seniors. However, long-term use of tramadol has serious adverse effects, including cognitive impairment. Besides its memory effects, already demonstrated in animals, a recent clinical report suggests that tramadol could also affect executive function in seniors. Several studies have hypothesized that the anti-muscarinic properties of tramadol could be responsible for the deleterious effects of tramadol on cognition.

OBJECTIVES

We aimed at investigating the effects of chronic administration of tramadol on cognitive flexibility in adult male mice, as assessed by a visual discrimination reversal task using a touchscreen device. The effects of tramadol were further compared to those of scopolamine, a reference muscarinic antagonist.

RESULTS

We found that, during the early phase of the reversal task, when cognitive flexibility is most in demand, both tramadol-treated mice (20 mg/kg, s.c., twice a day) and scopolamine-treated mice (0.5 mg/kg, s.c., twice a day) needed more correction trials and showed a higher perseveration index than saline-treated mice. Therefore, tramadol affects cognitive flexibility, and its anticholinergic properties could be at least partly involved in these deficits.

CONCLUSIONS

In view of these deleterious cognitive effects of tramadol, physicians should be cautious when prescribing this analgesic, especially in seniors who are more vulnerable to adverse drug events and in which alternative prescription should be preferred whenever possible.

Free Testosterone and Prolactin Levels and Sperm Morphology and Function Among Male Patients With Tramadol Abuse: A Case-Control Study

BACKGROUND/PURPOSE

Tramadol abuse has become a crisis in Egypt and many other Middle Eastern countries. Tramadol abuse is associated with sexual dysfunction and male infertility, according to recent animal and human studies. The objective of this study was to compare tramadol abuse patients and healthy controls regarding free testosterone and prolactin levels and semen analysis.

METHODS

Sixty patients with opiate use disorders attributed to tramadol (OUD-T) based on Diagnostic and Statistical Manual of Mental Disorders (Fifth Edition) diagnostic criteria and 30 healthy controls were included in the study. Sociodemographic and clinical data and urine, blood, and semen samples were collected from patients and controls for assessment.

RESULTS

Compared with controls, OUD-T patients had higher prolactin and lower free testosterone levels. Patients with OUD-T were more likely to have lower sperm count and higher abnormal motility and forms of sperms compared with controls.

CONCLUSIONS

Patients with OUD-T were found to be more likely to have lower free testosterone levels and lower sperm counts and vitality, and higher prolactin levels and sperm abnormal forms compared with controls.

Opioid Use and Driving Performance

INTRODUCTION

The USA is in an opioid epidemic, with an increased number of individuals taking psychoactive drugs while executing the tasks of everyday life, including operating a motor vehicle. The pharmacology of opioids has been widely studied, but the effects of opioids on psychomotor function, driving performance, and the risk of motor vehicle collision remain less clear. Clinicians are faced with the challenge of controlling patient pain while also reconciling conflicting messages from the literature about how safe it is for their patients taking opioids to engage in potentially dangerous routine tasks.

DISCUSSION

This review assesses the current literature regarding opioids as they relate to neurocognitive function, driving performance, and accident risk. Manuscripts are categorized by study context and subject matter: controlled experimental administration, illicit use, prescription use, retrospective forensic toxicology, and polydrug consumption.

CONCLUSION

Illicit use, initiation of therapy, and opioid use in combination with other psychoactive medications are contexts most clearly associated with impairment of driving-related functions and/or operation of a motor vehicle. Clinicians should counsel patients on the risk of impairment when initiating therapy, when co-prescribing opioids and other psychoactive drugs, or when a patient is suspected of having an opioid use disorder.

Cognitive impairment in patients diagnosed with tramadol dependence compared to healthy controls

Cognitive impairment is one of the consequences of substance use. We aimed to estimate the prevalence and correlates of cognitive impairment among patients with tramadol dependence in comparison with healthy controls. The sample consisted of 30 patients with tramadol dependence and 30 healthy controls. Cognitive functions were assessed using Benton Visual Retention Test- revised, Trail Making Test A and B and Wechsler Memory Scale. Patients were also subjected to the Structured Clinical Interview for diagnostic and statistical manual of mental disorders-fourth edition (DSM-IV) Axis I Disorder, the Structured Clinical Interview for DSM-IV Axis II Disorders and the Addiction Severity Index. Results showed that tramadol-dependence patients performed significantly worse than controls regarding cognitive functions, mainly manifested in impaired visual memory, visual reconstruction ability and processing, delayed memory, attention and processing speed, and visual, auditory, immediate, delayed and working memory. We found a nonsignificant negative correlation between cognitive performance and the age of patients or duration of tramadol use. Patients with tramadol dependence were more likely to have cognitive impairment than controls. This may have important clinical implications in determining the right academic and vocational programs for these individuals and adding skills training (e.g. problem solving) to their standard psychosocial treatment.

Cognitive Impairment among People Who Use Heroin and Fentanyl: Findings from the Miami Adult Studies on HIV (MASH) Cohort

Background: Cognitive impairment is common in people living with HIV (PLWH). Opioid drugs exert direct and indirect effects on cognitive processes, which may contribute to cognitive dysfunction among PLWH. This study was designed to determine if opioid use is associated with cognitive impairment and whether the effect differs between PLWH and HIV-uninfected adults. Other neuropsychiatric symptoms, such as depression and apathy, were also examined. We conducted a cross-sectional analysis of 265 PLWH and 284 HIV-uninfected participants from the Miami Adult Studies on HIV (MASH) cohort. The Mini-Mental State Examination (MMSE) was used to assess cognitive impairment. Substance use was self-reported. Overall, 26.8% of PLWH and 15.1% of HIV-uninfected used opioids. Cognitive impairment was more frequent among people who used heroin and/or fentanyl than those who misused prescription opioids (31.6% vs. 10.5%, p = .005). The use of heroin/fentanyl was associated with increased odds for cognitive impairment (adjusted OR: 2.21, 95% CI 1.05-4.64, p = .036). Among PLWH only, the misuse of opioids was associated with a higher frequency of neuropsychiatric symptoms such as depression and apathy. A higher risk for cognitive impairment was seen among people who used heroin and fentanyl. PLWH who misuse opioids may be at an increased risk for neuropathology, but elucidation of mechanisms for opioid-induced cognitive deficits is needed.

Acute toxicity related to misuse (nonmedical use) of tramadol: Experience of the European Drug Emergencies Network Plus

Following the development of the tramadol crisis currently affecting countries in the Middle East, and Africa, there has been increasing international interest in the regulation of tramadol. This study investigates the misuse of tramadol in patients presenting to emergency departments across Europe. Data from 32 emergency departments in 21 countries were extracted from the Euro-DEN Plus database for the 4-year period from 1 January 2014 to 31 December 2017. Of the reported 24,957 emergency department presentations, tramadol misuse was reported in 105 (0.4% presentations). Tramadol misuse was most common in Bratislava (Slovakia; n = 11, 7.5% of all presentations to this centre), Riga (Latvia; n = 4, 4.9%) and Munich (Germany; n = 17, 2.9%). On arrival, 14 (13.3%) of presentations were in coma/Glasgow coma score ≤ 8 and 9 of these had a respiratory rate <12 breaths/min. These presentations potentially pose a significant burden on emergency departments with a large proportion requiring admission to hospital for ongoing care.

Population Size Estimation of Tramadol Misusers in Urban Population in Iran: Synthesis of Methods and Results

Background

Estimating the population who use drugs is essential for planning, monitoring, and evaluation of substance use prevention and treatment. This study aims to estimate the population who misuse tramadol in urban population in Iran.

Methods

We used the wisdom of the experts (WOTE) and network scale-up (NSU) methods to calculate the population of tramadol misusers in 10 provincial capitals of Iran, in 2016. The WOTE was conducted among pharmacists in drugstores and the personnel of traditional medicinal herbs stores. They guessed the best estimation of tramadol misusers population in their cities. The NSU method was conducted among the general population and participants were questioned about ever and daily, non-medical use of tramadol during last 12 months in their network. The median of the methods was used to calculate the proportion of the adult population (15-49 years old).

Findings

The population size of tramadol misusers in studied cities was 83300 [95% uncertainty limits (UL): 47960-256220]. This corresponded to 6.6 per 1000 (95% UL: 3.88-20.30) of the 15-49-year-old population. The projected number of tramadol misusers for all 31 provincial capitals was 118290 (95% UL: 68100-363130840) and 212440 (95% UL: 122310-653410) for all urban areas. NSU also estimated the number of people who misuse tramadol on daily basis. These numbers were 52000 (95% UL: 19940-176570) for studied cities, 73840 (95% UL: 28320-250740) for all 31 provincial capital cities, and 132610 (95% UL: 50860-450310) for all urban areas in Iran.

Conclusion

This study presents information on high prevalence of tramadol misuse in urban population. We need national control measures and demand reduction programs to control tramadol misuse.

Acute tramadol enhances brain activity associated with reward anticipation in the nucleus accumbens

BACKGROUND

Tramadol is an analgesic with monoamine reuptake inhibition and μ-opioid receptor activation. Although tramadol has been widely used for treatment of various pain conditions, there is controversy over the risk of abuse potential. We examined the effects of tramadol on the reward system in humans using functional magnetic resonance imaging (fMRI) to assess the potential of tramadol for drug abuse or dependence.

METHODS

A randomized, double-blind, placebo-controlled, crossover study was conducted for 19 healthy adults under tramadol or placebo. In association with subjective mood questionnaires, monetary incentive delay (MID) task was performed to assess the neural response to reward anticipation during fMRI. Subjective mood measures and blood oxygenation level-dependent (BOLD) signal during gain and loss anticipation were compared between tramadol and placebo.

RESULTS

Tramadol significantly reduced anxiety (Z = - 2.513, p = 0.012) and enhanced vigor (Z = - 2.725, p = 0.006) compared with placebo. By Mood Rating Scale, tramadol provoked contented (Z = - 2.316, p = 0.021), relaxed (Z = - 2.236, p = 0.025), and amicable feelings (Z = - 2.015, p = 0.044) as well as increased alertness (Z = - 1.972, p = 0.049) and contentedness domains (Z = - 2.174, p = 0.030) compared with placebo. Several brain regions including nucleus accumbens (NAc) were activated during gain anticipation in the MID task under both tramadol and placebo. Tramadol increased the %BOLD signal change in NAc at +¥500 cue significantly more than the placebo (Z = - 2.295, p = 0.022).

CONCLUSION

Tramadol enhances the reward system and thereby may have abuse potential or precipitate drug abuse in human.

Cross state-dependency of learning between tramadol and MK-801 in the mouse dorsal hippocampus: involvement of nitric oxide (NO) signaling pathway

RATIONALE

Tramadol, an atypical μ-opioid receptor agonist, as a psychoactive drug, is frequently abused by human beings. Understanding the neurobiological mechanisms of drug-associated learning and memory formation may help prevent drug addiction and relapse. Previous study revealed that dorsal hippocampus (CA1) plays a crucial role in the retrieval of tramadol-associated memory and that its role depends on the expression of CA1 N-methyl-D-aspartate (NMDA) receptors (Jafari-Sabet et al. Can J Physiol Pharmacol 96:45-50, 2018).

OBJECTIVE

To clarify the exact mechanisms involved, the activation of CA1 nitric oxide (NO) signaling pathway by L-arginine (a nitric oxide precursor) on the interaction between tramadol and MK-801 in memory retrieval was examined. The dorsal hippocampal CA1 regions of adult male NMRI mice were bilaterally cannulated and a single-trial step-down inhibitory avoidance apparatus was used for the assessment of memory retrieval.

RESULTS

Post-training and/or pre-test microinjection of tramadol (0.5 and 1 μg/mouse) and/or a non-competitive NMDA receptor antagonist, MK-801 (0.25 and 0.5 μg/mouse), induced amnesia which were reversed when the same doses of the drugs were administered 24 h later in a pre-test session, suggesting tramadol state-dependent learning (SDL) and MK-801 SDL. The amnesia induced by post-training microinjection of tramadol (1 μg/mouse) was reversed by pre-test microinjection of MK-801 (0.25 and 0.5 μg/mouse). Pre-test microinjection of MK-801 (0.125 and 0.25 μg/mouse) with an ineffective dose of tramadol (0.25 μg/mouse) potentiated tramadol SDL. The amnesia induced by post-training microinjection of MK-801 (0.5 μg/mouse) was reversed by pre-test microinjection of tramadol (0.5 and 1 μg/mouse). Pre-test microinjection of tramadol (0.25 and 0.5 μg/mouse) with an ineffective dose of MK-801 (0.125 μg/mouse) potentiated MK-801 SDL. Pre-test microinjection of ineffective doses of L-arginine (0.125, 025, and 0.5 μg/mouse) improved amnesia induced by the co-administration of tramadol and MK-801. Pre-test microinjection of L-arginine (0.125, 025, and 0.5 μg/mouse) could not reverse amnesia induced by post-training microinjection of tramadol while same doses of L-arginine improved MK-801 response on tramadol SDL.

CONCLUSION

The results strongly propose that activation of CA1 NO signaling pathway has a pivotal role in cross SDL among tramadol and MK-801.