Inhalants are volatile substances producing vapors that can be taken intentionally via the pulmonary route to produce a mind-altering "buzz" or high. Inhalants are dangerous and their use represents a vast abuse problem in the United States and abroad. At greatest risk of harm from these drugs are adolescents in their early teenage years. Most inhalants are central nervous system (CNS) depressants, but they also cause adverse medical effects on almost every organ system. Both short- and long-term toxic effects occur. Short-term effects include diplopia, memory impairment, slurred speech, seizure, or death from cardiac arrhythmias. Long-term chronic effects include permanent ataxias or peripheral neuropathies, blindness, cognitive impairment, dementia, and renal toxicity.
Recreational use of inhalants in the United States increased in the 1950s and is now widespread amongst adolescents. More than 3000 abusable products containing volatile chemicals are legal and readily obtained; these include solvents, adhesives, fuels, dry-cleaning agents, cigarette lighters, permanent markers, correction fluid, and aerosols with propellants used in whipped cream, deodorants, paints, electronic cleaning sprays, and cooking sprays. These products are readily available, easy to purchase, not illegal to possess, easy to conceal, and are found in every household or garage. They offer a quick-onset high of brief duration, lessening the chances of getting caught. Prosecution of offenders tends to be minimal, and few states have laws prohibiting inhalant abuse.
The most commonly abused inhalants are the aromatic hydrocarbons, aliphatic hydrocarbons, alkyl halides, and nitrites.
Aromatic hydrocarbons, such as toluene and xylene, are the most commonly used inhalants of abuse. This is because they cause an intense euphoric rush when inhaled. They are found in markers, adhesive cements, model glues, paint thinners, and spray paints, with the highest concentration found in gold and silver spray paint.
Aliphatic hydrocarbons are volatile fuels such as propane, butane (cigarette lighter fluid), and gasoline.
Alkyl halides, 1,1,1-trichloroethane or trichloroethylene, are found in cleaning fluids, typewriter correction fluid, and compressed air for cleaning electronics.
Nitrites, such as amyl nitrites, are found in room air fresheners, video head cleaner, and leather cleaner. These agents, commonly known as "poppers" or "snappers" are used to enhance sexual activity.
Sniffing - Inhaling vapors from an open container
Huffing - Soaking a rag or sock with substance and placing it over the mouth and nose
Bagging - Spraying or pouring the substance into a paper or plastic bag and inhaling the vapors by placing the bag over the face or over the head
Dusting - Inhaling vapors directly from electronic equipment cleaning aerosols
Street names in inhalant abuse include air blast, aroma of men, bolt, bopper, bullet, discorama, dusting, glading, gluey, hardware, head cleaner, hippie crack, laughing gas, locker room, pearls, popper, quicksilver, rush, shoot the breeze, snapper, Texas shoe shine, thrust, tolly, and whiteout.
Inhalants are highly lipid soluble; they easily cross both alveolar membranes in the lungs and the blood-brain barrier to reach high concentrations in the brain. Inhalation avoids first-pass hepatic metabolism so the onset is fast. The onset is seen in a few seconds, with a peak plasma concentration 15-30 minutes after inhalation. The inhaled concentration depends on the mode of administration. Sniffing offers the lowest concentration, followed by huffing, and bagging offers the highest concentration. With a few exceptions, elimination occurs primarily through the lungs, with many inhaled compounds eliminated unchanged by exhalation. Some of the inhalants, including alkyl nitrites, aromatics, and methylene chloride, undergo significant hepatic metabolism that can produce damaging free nitrites and toxic carbon monoxide as byproducts.
The mechanism of inhalant's effects is not fully understood. Pharmacologic properties of all inhalants vary, contributing to different gas potentials, solubility in the blood, and elimination, which leads to slight differences in their actions, intoxicating effects, and abuse potential. Some authors propose the action of some is similar to the action of ethanol. They suggest the action is to stimulate the gamma-aminobutyric acid (GABA) and the glycine a1 receptors, as well as inhibit the N -methyl-D -aspartate (NMDA) receptor, leading to inhibition in the CNS. Riegel et al proposed that toluene activates dopamine release in key brain regions.  Other proposed mechanisms include induced changes in neuronal cell membranes. Nitrites, used primarily as sexual enhancers, dilate blood vessels. More research is needed to better define the mechanisms of action of all inhalants.
Inhalant abuse is common among adolescents; more than 2 million children aged 12-17 years are reported to have used inhalants at least once in their lifetime. According to the 2010 National Survey on Drug Use and Health (NSDUH), 793,000 people aged 12 or older had used inhalants for the first time in the last 12 months, 68.4% of those were younger than 18 years. The most recent report by Monitoring the Future Study (MTF), a survey funded by the National Institute of Drug Abuse (NIDA) that monitors drug abuse in adolescents from grades 8-12, reported that inhalant abuse remains highest among eighth graders and prevalence for all age groups has remained relatively stable over the past few years. Inhalant abuse remains highest among eighth graders, with 7% reporting use in the last 12 months. All age cohorts (8, 10, and 12 y) have shown consistent decline since 2007.
In the United States, inhalant abuse usually precedes tobacco and alcohol experimentation. Although most teenagers outgrow inhalant use, many progress to "harder" drugs, including marijuana and cocaine.
Inhalant abuse is less common (though not rare) in adults. Those especially at risk are doctors, nurses, factory workers, dentists, shoemakers, hair stylists, painters, and dry-cleaning workers; all with ready access to chemicals or anesthetics. Besides the chemical high offered by these drugs, some adults seek an additional aphrodisiac effect reported to occur with some of these chemicals. Nitrite inhalant use, for example, is prevalent amongst homosexual males. In one survey, 69% of homosexual males sampled had experience with nitrite inhalants.
These drugs have no social or geographic boundaries, but children abusing inhalants tend to be of lower socioeconomic class, poor performers in school with high rates of absenteeism, and from broken homes.
Across the globe, inhalant abuse is rampant among children in both industrial nations and developing countries. Countries with particularly high abuse rates include Great Britain, Singapore, and Brazil.
Inhalant abuse is associated with significant morbidity and mortality. The debilitating and potentially lethal effects of inhalants can occur even with the first use. Although inhalant deaths are underreported in the United States, the 2005 report of the National Inhalant Prevention Coalition (NIPC) reports 100-125 deaths annually as a result of inhalant abuse.  Another study by Alper et al found that toluene was associated with an increased QT interval in abusers with a history of unexplained syncope.  Additional medical conditions associated with inhalant abuse include acute, severe acute cardiomyopathy(toluene),  vision loss (methanol),  severe angioedema (dusters),  and acute or chronic myocardial ischemia (butane). 
Asphyxiation can result from the displacement of oxygen in the lungs by prolonged or repeated inhalations. Suffocation can occur if a plastic bag is placed over the head when inhaling the fumes and the user becomes unconscious. Death can also occur because of complications of the intoxication suchas choking on aspirated gastric contents, fire-related injuries from inhalant combustion, or fatal injuries suffered as a result of high-risk behaviors.
A common cause of death in inhalant abusers is called sudden sniffing death syndrome (SSDS). Although the exact mechanism is unknown, the inhalant is believed to sensitize the myocardium to circulating catecholamines. This causes an exaggerated response to epinephrine released during a sudden alarm or increased physical activity that leads to a fatal arrhythmia. Death usually occurs while the user is running, attempting to flee, experiencing a particularly frightful hallucination, or during sexual activity. The co-ingestion of a sympathomimetic agent, such as cocaine or even therapeutic Ritalin, may increase the risk of the fatal arrhythmia. Sudden sniffing death is particularly associated with the abuse of toluene, butyl nitrate, butane, propane, and chemicals in aerosols.
Inhalant abuse rates are higher in Whites, although use is also high among Hispanic and Native American children.
In the past, abuse was more prevalent in males, but over the past 2 decades, abuse has increased in females and the prevalence is now nearly equal in the youth population. Inhalant abuse still tends to be higher in adult males.
The typical abusers of inhalants are aged 10-15 years, although use in children as young as 7 and 8 years has been reported. The average age of initial use of these chemicals was around 10 years in one study, which preceded the average initiation into cigarettes by 1.5 years and narcotics by almost 4 years. Experimentation typically occurs in late childhood and is short lived. Chronic abuse is usually seen in older adolescents, although it has also been reported as late as the fifth and sixth decades of life.
Inhalant use leads to an earlier initiation of other drug use, including cigarettes and alcohol, and is associated with a higher lifetime prevalence of substance use disorders.
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