Volatile substance misuse : clinical considerations, neuropsychopharmacology and potential role of pharmacotherapy in management

Non-endemic skeletal fluorosis: Causes and associated secondary hyperparathyroidism (case report and literature review)

Skeletal fluorosis (SF) is endemic primarily in regions with fluoride (F)-contaminated well water, but can reflect other types of chronic F exposure. Calcium (Ca) and vitamin D (D) deficiency can exacerbate SF. A 51-year-old man with years of musculoskeletal pain and opiate use was hypocalcemic with secondary hyperparathyroidism upon manifesting recurrent long bone fractures. He smoked cigarettes, drank large amounts of cola beverage, and consumed little dietary Ca. Then, after 5 months of Ca and D₃ supplementation, serum 25(OH)D was 21 ng/mL (Nl, 30-100), corrected serum Ca had normalized from 7.8 to 9.4 mg/dL (Nl, 8.5-10.1), alkaline phosphatase (ALP) had decreased from 1080 to 539 U/L (Nl, 46-116), yet parathyroid hormone (PTH) had increased from 133 to 327 pg/mL (Nl, 8.7-77.1). Radiographs revealed generalized osteosclerosis and a cystic lesion in a proximal femur. DXA BMD Z-scores were +7.4 and +0.4 at the lumbar spine and "1/3" radius, respectively. Bone scintigraphy showed increased uptake in two ribs, periarticular areas, and proximal left femur at the site of a subsequent atraumatic fracture. Elevated serum collagen type I C-telopeptide 2513 pg/mL (Nl, 87-345) and osteocalcin >300 ng/mL (Nl, 9-38) indicated rapid bone turnover. Negative studies included hepatitis C Ab, prostate-specific antigen, serum and urine electrophoresis, and Ion Torrent mutation analysis for dense or high-turnover skeletal diseases. After discovering markedly elevated F concentrations in his plasma [4.84 mg/L (Nl, 0.02-0.08)] and spot urine [42.6 mg/L (Nl, 0.2-3.2)], a two-year history emerged of "huffing" computer cleaner containing difluoroethane. Non-decalcified histology of a subsequent right femur fracture showed increased osteoblasts and osteoclasts and excessive osteoid. A 24-hour urine collection contained 27 mg/L F (Nl, 0.2-3.2) and <2 mg/dL Ca. Then, 19 months after "huffing" cessation and improved Ca and D₃ intake, yet with persisting bone pain, serum PTH was normal (52 pg/mL) and serum ALP and urine F had decreased to 248 U/L and 3.3 mg/L, respectively. Our experience combined with 15 publications in PubMed concerning unusual causes of non-endemic SF where the F source became known (19 cases in all) revealed: 11 instances from high consumption of black tea and/or F-containing toothpaste, 1 due to geophagia of F-rich soil, and 7 due to "recreational" inhalation of F-containing vapors. Circulating PTH measured in 14 was substantially elevated in 2 (including ours) and mildly increased in 2. The severity of SF in the cases reviewed seemed to reflect cumulative F exposure, renal function, and Ca and D status. Several factors appeared to influence our patient's skeletal disease: i) direct anabolic effects of toxic amounts of F on his skeleton, ii) secondary hyperparathyroidism from degradation-resistant fluorapatite bone crystals and low dietary Ca, and iii) impaired mineralization of excessive osteoid due to hypocalcemia.

The Neuroscience of Drug Reward and Addiction

Drug consumption is driven by a drug's pharmacological effects, which are experienced as rewarding, and is influenced by genetic, developmental, and psychosocial factors that mediate drug accessibility, norms, and social support systems or lack thereof. The reinforcing effects of drugs mostly depend on dopamine signaling in the nucleus accumbens, and chronic drug exposure triggers glutamatergic-mediated neuroadaptations in dopamine striato-thalamo-cortical (predominantly in prefrontal cortical regions including orbitofrontal cortex and anterior cingulate cortex) and limbic pathways (amygdala and hippocampus) that, in vulnerable individuals, can result in addiction. In parallel, changes in the extended amygdala result in negative emotional states that perpetuate drug taking as an attempt to temporarily alleviate them. Counterintuitively, in the addicted person, the actual drug consumption is associated with an attenuated dopamine increase in brain reward regions, which might contribute to drug-taking behavior to compensate for the difference between the magnitude of the expected reward triggered by the conditioning to drug cues and the actual experience of it. Combined, these effects result in an enhanced motivation to "seek the drug" (energized by dopamine increases triggered by drug cues) and an impaired prefrontal top-down self-regulation that favors compulsive drug-taking against the backdrop of negative emotionality and an enhanced interoceptive awareness of "drug hunger." Treatment interventions intended to reverse these neuroadaptations show promise as therapeutic approaches for addiction.

The impact of subsidized low aromatic fuel (LAF) on petrol (gasoline) sniffing in remote Australian indigenous communities

Background

Since 2005, the Australian Government has subsidized the production and distribution of Low Aromatic Fuel (LAF) as a deterrent against petrol (gasoline) sniffing in remote Indigenous communities. LAF is used in place of unleaded petrol as a fuel for vehicles and other engines. This paper reports findings from an independent evaluation of the LAF rollout.

Methods

Forty one Indigenous communities were surveyed between 2010 and 2014, with each community being visited twice at a two yearly interval. Quantitative data on prevalence of petrol sniffing were collected, as well as qualitative data on the acceptability of LAF, evidence of substitution for inhaled petrol with other drugs, and programs such as recreational, training and employment opportunities. Prevalence rates of sniffing per 1000 population for each survey year and community were calculated by dividing the total number of sniffers by the population aged 5–39 years and multiplying by 1000.

Results

Between 2011–12 and 2013–14, the total estimated number of people sniffing petrol declined from 289 to 204, a fall of 29.4%. At both times, the median petrol sniffing prevalence rate was lower in communities with LAF than in communities without LAF. In 17 of the 41 communities, comparable data were available over a longer period, commencing in 2005–06. Fifteen of these communities stocked LAF over the entire period. In these communities, the median rate of petrol sniffing declined by 96%, from 141.6 per 1000 population in 2005–06 to 5.5 in 2013–14 (p < 0.05). LAF was widely accepted, although acceptance was often qualified by a belief that LAF harmed engines. Anecdotal reports suggest that the fall in petrol sniffing may have been offset by increased use of cannabis and other drugs, but the relationship is not one of simple cause-and-effect, with evidence that an increase in cannabis use in communities commenced before the LAF rollout began. Provision of services in communities has improved in recent years, but many programs continue to be inadequately resourced.

Conclusions

The rollout of LAF appears to have contributed to reducing petrol sniffing and associated harms in Australian Indigenous communities.

Laboratory approach for diagnosis of toluene-based inhalant abuse in a clinical setting

The steady increase of inhalant abuse is a great challenge for analytical toxicologists. This review describes an overview of inhalant abuse including the extent of the problem, types of products abused, modes of administration, pharmacology and effects of inhalants, the role of laboratory, interpretation of laboratory results and clinical considerations. Regular laboratory screening for inhalant abuse as well as other substance abuse and health risk behaviors must be a part of standard clinical care.

Adolescent inhalant use prevention, assessment, and treatment: A literature synthesis

Inhalant use refers to the use of substances such as gases, glues, and aerosols in order to achieve intoxication, while inhalant use disorder (IUD) encompasses both DSM-IV-TR criteria for inhalant abuse and dependence. Inhalant use among adolescents is an international public health concern considering the severe medical and cognitive consequences and biopsychosocial correlates. In this paper, we summarize the current state of the literature on inhalant use among adolescents focusing on social context, prevention, assessment, and treatment strategies. Psychoeducation, skills training, and environmental supply reduction are helpful strategies for preventing adolescent inhalant use, while parent and adolescent self-report as well as physician report of medical signs and symptoms can aid in assessment and diagnosis. Although research has only begun to explore the treatment of inhalant use, preliminary findings suggest that a multimodal approach involving individual counselling (i.e., CBT brief intervention), family therapy, and activity and engagement programs is the first-line treatment, with residential treatment programs indicated for more severe presentations. The limited nature of treatments developed specifically for inhalant use combined with high prevalence rates and potential for significant impairment within the adolescent population indicate the need for further research. Research should focus on understanding the social context of use, establishing the efficacy of current adolescent substance use treatments adapted for inhalant use, and exploring long-term outcomes.

Acute reversible neurologic deficits due to ethyl chloride sniffing: a case report and review of literature

Ethyl chloride (CH3CH2Cl) or chloroethane is a colorless volatile halogenated hydrocarbon gas found in many commercially available solvents, and it may be used as an inhalant of abuse. Neurologic toxicity has been reported, as well as deaths. We present a case of a 47-year-old HIV-positive man who presented with acute reversible neurologic deficits secondary to inhalational exposure to ethyl chloride. Laboratory studies and neuroimaging are nondiagnostic in ethyl chloride-induced neurotoxicity and thus requires a high index of clinical suspicion. The mainstay of treatment is supportive with withdrawal of the offending agent and observation for resolution of neurologic symptoms.

Patterns of substance use, delinquency, and risk factors among adolescent inhalant users

BACKGROUND

Despite insidious effects, use of inhalant substances by adolescents remains an understudied phenomenon.

OBJECTIVE

This research was designed to identify patterns of past year substance use and delinquency among adolescent inhalant users.

METHOD

The study used a sample of adolescent inhalant users (ages ranged from 12-17 years, n = 7,476) taken from a pooled sample of the 2002 through 2012 National Survey of Drug Use and Health (NSDUH). Three-step latent class analyses were conducted with past year substance use and delinquency behaviors as class indicators. Demographic and social covariates were included in the analyses.

RESULTS

Analyses yielded a six-class solution comprised of classes of users characterized by low substance use/low delinquency, high substance use/low delinquency, low substance use/fighting, cigarettes/alcohol/marijuana, high substance use/high delinquency, and cigarettes/alcohol/ marijuana/opioids/moderate delinquency.

CONCLUSIONS

Findings provide insight into the taxonomy of adolescent inhalant user heterogeneity, and may inform future efforts at detection and prevention of inhalant use by suggesting warning signs of co-occurring externalizing behaviors and possible indications of underlying internalized issues.

Effects of the abused inhalant toluene on the mesolimbic dopamine system

Toluene is a representative member of a class of inhaled solvents that are voluntarily used by adolescents and adults for their euphorigenic effects. Research into the mechanisms of action of inhaled solvents has lagged behind that of other drugs of abuse despite mounting evidence that these compounds exert profound neurobehavioral and neurotoxicological effects. Results from studies carried out by the authors and others suggest that the neural effects of inhalants arise from their interaction with a discrete set of ion channels that regulate brain activity. Of particular interest is how these interactions allow toluene and other solvents to engage portions of an addiction neurocircuitry that includes midbrain and cortical structures. In this review, we focus on the current state of knowledge regarding toluene's action on midbrain dopamine neurons, a key brain region involved in the initial assessment of natural and drug-induced rewards. Findings from recent studies in the authors' laboratory show that brief exposures of adolescent rats to toluene vapor induce profound changes in markers of glutamatergic plasticity in VTA DA neurons. These changes are restricted to VTA DA neurons that project to limbic structures and are prevented by transient activation of the medial prefrontal cortex prior to toluene exposure. Together, these data provide the first evidence linking the voluntary inhalation of solvents to changes in reward -sensitive dopamine neurons.

Exposure to household painting and floor treatments, and parental occupational paint exposure and risk of childhood brain tumors: results from an Australian case-control study

PURPOSE

Childhood brain tumors (CBT) are the leading cause of cancer death in children, yet their etiology remains largely unknown. This study investigated whether household exposure to paints and floor treatments and parental occupational painting were associated with CBT risk in a population-based case-control study conducted between 2005 and 2010.

METHODS

Cases were identified through all ten Australian pediatric oncology centers, and controls via nationwide random-digit dialing, frequency matched to cases on age, sex, and state of residence. Data were obtained from parents in mailed questionnaires and telephone interviews. Information on domestic painting and floor treatments, and parental occupational exposure to paint, in key periods relating to the index pregnancy and childhood was obtained for 306 cases and 950 controls. Data were analyzed using unconditional logistic regression, adjusting for frequency matching variables and potential confounders.

RESULTS

Overall, we found little evidence that parental, fetal, or childhood exposure to home painting or floor treatments was associated with risk of CBT. There was, though, some evidence of a positive association between childhood exposure to indoor painting and risk of high-grade glioma [odds ratio (OR) 3.31, 95 % confidence interval (CI) 1.29, 8.52] based on very small numbers. The OR for the association between CBT and paternal occupational exposure to paint any time before the pregnancy was 1.32 (95 % CI 0.90, 1.92), which is consistent with the results of other studies.

CONCLUSIONS

Overall, we found little evidence of associations between household exposure to paint and the risk of CBT in any of the time periods investigated.