Inhalants are a broad range of drugs in the forms of gases, aerosols, or solvents which are breathed in and absorbed through the lungs. While some inhalant drugs are used for medical purposes, as in the case of nitrous oxide (a dental anaesthetic), this article focuses on the non-medical use of inhalants, as recreational drugs which are used for their intoxicating effect. Most inhalant drugs which are used non-medically are ingredients in household or industrial chemical products which are not intended to be concentrated and inhaled, including organic solvents (found in cleaning products, fast-drying glues, and nail polish removers), fuels (gasoline (petrol) and kerosene) and propellant gases such as freon and compressed hydrofluorocarbons which are used in aerosol cans such as hairspray and non-stick cooking spray. A small number of recreational inhalant drugs are pharmaceutical products which are used illicitly, such as anaesthetics (ether and nitrous oxide) and volatile anti-angina drugs (alkyl nitrites).
Inhalant users tend to be people who do not have access to other drugs or alcohol, such as children, teenagers, incarcerated or institutionalized people, and marginalized individuals. The most serious inhalant abuse occurs among children and teens who "...live on the streets completely without family ties." Inhalant users inhale vapor or aerosol propellant gases using plastic bags held over the mouth or by breathing from a solvent-soaked rag or an open container. The effects of inhalants range from an alcohol-like intoxication and euphoria to hallucinations, depending on the substance and the dosage. Some inhalant users are injured due to the harmful effects of the solvents or gases, or due to other chemicals used in the products that they are inhaling. As well, as with any recreational drug, users can be injured due to dangerous behavior while they are intoxicated, such as driving under the influence. In some cases, users have died from hypoxia (lack of oxygen), pneumonia, cardiac failure or arrest , or aspiration of vomit.
Industrial and automotive products also contain solvents and propellant gases that are used as inhalants. Solvents such as toluene are found in turpentine, gasoline, paint, spraypaint, and a range of quick-drying adhesives and cements (e.g., rubber cement and plastic cement). The solvent diethyl ether is used in an aerosol product called "automotive starting fluid", which mixes 20-60% diethyl ether with petroleum distillates such as hexane and heptane. Canisters of butane are used as camping fuel for small campstoves.
Nitrite drugs such as amyl nitrite are volatile liquids which are inhaled. While they are used medically to treat heart diseases such as angina and to treat cyanide poisoning, several nitrite drugs (nicknamed "poppers") are also used as an inhalant drug in the gay subculture and in the rave dance scene, due to their euphoric effect. While nitrite drugs are regulated by a variety of federal, state, and local regulations and legal restrictions, several nitrite products can be found in legally-available products. Amyl nitrite is available as an over-the-counter drug in some areas; butyl nitrite is sold as a room deodorizer under trade names as "RUSH" and "Locker Room"; and alkyl nitrite is an ingredient in video head cleaner or some brands of nail polish remover.
The effects of solvent intoxication can vary widely depending on the dose and what type of solvent or gas is inhaled. A person who has inhaled a small amount of rubber cement or paint thinner vapour may be impaired in a manner resembling alcohol inebriation - stimulation, a sense of euphoria and intoxication, followed by a period of depression. A person who has inhaled a larger quantity of solvents or gases, or a stronger chemical, may experience stronger effects such as distortion in perceptions of time and space, hallucinations, and emotional disturbances.
In the short term, many users experience headache, nausea and vomiting, slurred speech, loss of motor coordination, and wheezing. A characteristic "glue sniffer's rash" around the nose and mouth is sometimes seen after prolonged use. An odor of paint or solvents on clothes, skin, and breath is sometimes a sign of inhalant abuse, and paint or solvent residues can sometimes emerge in sweat.
This makes inhaled anesthetic gases different to other NMDA antagonists such as ketamine, which bind to a regulatory site on the NMDA-sensitive calcium transporter complex and provide slightly lower levels of NMDA blockade, but for a longer and much more predictable duration. This makes a deeper level of anesthesia achievable more easily using anaesthetic gases, but can also make them more dangerous than other drugs used for this purpose.
Alcohol is known to act as a GABA agonist, and it is likely that other solvents also act here to produce additional depressant effects. The solvent diethyl ether, for instance, has seen historical episodes of both inhalation and drinking, and produces effects suggestive of both NMDA and GABA mediated activity. The particular mix of NMDA antagonist vs GABA agonist properties will vary between solvents depending on molecular size or shape, and so the effects of particular solvents will differ, although all tend to share a similar profile.
Of more concern from a toxicological perspective, or from the point of view of an individual considering the recreational use of solvents, is the additional toxicity resulting from either the physical properties of the compound itself, or additional ingredients present in a product. Many solvents of abuse are fairly toxic compounds which often produce liver and brain damage after prolonged use. This is particularly detrimental with chlorinated compounds such as carbon tetrachloride or chloroform, or when products containing mixtures of many substances such as solvent-based glue or paint is inhaled. Toxicity may also result from the pharmacological properties of the drug; excess NMDA antagonism can completely block calcium influx into neurons and provoke cell death through apoptosis, although this is more likely to be a long term result of chronic solvent abuse than a consequence of short term use.
Precise statistics on deaths caused by inhalant abuse are difficult to determine, as it is considered a dramatically under-reported cause of death due to the common result of a cause-of-death determination being attributed to the side-effects of inhalant abuse, such as a blood vessel rupture in the brain or a heart attack, rather than to the abuse itself. Inhalant use or abuse was mentioned on 144 death certificates in Texas during the period 1988-1998 and was reported in 39 deaths in Virginia between 1987 and 1996 from acute voluntary exposure to abused inhalants.
Hypoxia can occur when inhalant users are huffing from a plastic bag over their face, which means that they are not breathing enough fresh air. Also, since many solvents are highly flammable (e.g., gasoline, paint thinner), some users have suffered burn injuries and deaths due to fires. Female inhalant users who are pregnant may have adverse effects on the fetus and the baby may be smaller when it is born, and may need additional health care. There is some evidence of birth defects and disabilities in babies born to women who sniffed solvents such as gasoline. Driving while using solvents presents the same dangers as other types of impaired driving, because many solvents cause an alcohol-type intoxication.
Nitrous oxide gas can cause death by asphyxiation if a user inhales directly from a large tank using a mask or tube. Normally with recreational use, users get oxygen because they continue to breathe after inhaling the nitrous oxide from a bag or balloon. In a medical or dental setting, nitrous oxide is normally administered in combination with oxygen. With recreational use, if a mask is attached directly to the tank, then the user gets pure nitrous oxide with no way to take in any oxygen. The rapidly-expanding gas causes very cold temperatures which can freeze the lips and throat if the gas is inhaled directly from a tank or "whippit" aerosol container. Releasing the gas into a balloon first allows the gas to expand and warm before it is inhaled. Use of nitrous oxide does not damage the brain or liver, but it can cause vitamin B12 depletion.
Inhalant drugs are often used by children, teenagers, incarcerated or institutionalized people, and impoverished people, because these solvents and gases are ingredients in hundreds of legally-available, inexpensive products, such as deodorant sprays, hair spray, and aerosol air fresheners. However, most users tend to be "...adolescents (between the ages of 13 and 17) In some countries, chronic, heavy inhalant use is concentrated in marginalized, impoverished communities. Young people who become chronic,heavy inhalant abusers are also more likely to be those who are isolated from their families and community. The article Epidemiology of Inhalant Abuse: An International Perspective notes that "[t]he most serious form of obsession with inhalant use probably occurs in countries other than the United States where young children live on the streets completely without family ties. These groups almost always use inhalants at very high levels (Leal et al. 1978). This isolation can make it harder to keep in touch with the sniffer and encourage him or her to stop sniffing."
The article also states that "...high [inhalant use] rates among barrio Hispanics almost undoubtedly are related to the poverty, lack of opportunity, and social dysfunction that occur in barrios", and states that the "...same general tendency appears for Native-American youth", because "...Indian reservations are among the most disadvantaged environments in the United States; there are high rates of unemployment, little opportunity, and high rates of alcoholism and other health problems." There are a wide range of social problems associated with inhalant use such as feelings of distress, anxiety and grief for the community; violence and damage to property, violent crime, stresses on the juvenile justice system, and stresses on youth agencies and support services.
Chloroform was used as an anaesthetic, but it fell into disuse due to its high toxicity and narrow dose margin. Nitrous oxide and diethyl ether were adopted by the medical mainstream and became the standard anesthetics in use for many years. Other gases such as cyclopropane were also used for anesthesia. Non-flammable gases such as halothane replaced flammable anaesthetics such as ether. Halothane is now rarely used in humans due to problems with liver damage and a rare condition called malignant hyperthermia, but it is still widely used in veterinary medicine.
Modern anesthetics such as isoflurane and sevoflurane have been developed for medical use which lack both the flammability of ether and the toxicity of halothane, and research in the area is ongoing. Nitrous oxide is still widely used as a dental anaesthetic, to reduce patient anxiety during dental work and minor dental surgery. Other medical anesthetics and inhaled medicinal drugs include xenon, enflurane, isoflurane, sevoflurane, desflurane, methoxyflurane, salbutamol, and fluticasone.
In Canada, native children in the isolated Northern Labrador community of Davis Inlet were the focus of national concern in 1993 when many were found to be sniffing gasoline. The federal Canadian and provincial Newfoundland and Labrador governments intervened on a number of occasions, sending many children away for treatment. Despite being moved to the new community of Natuashish in 2002, serious inhalant abuse problems have continued. Similar problems were also reported in Sheshatshiu in 2000. In Mexico, the inhaling of a mixture of gasoline and/or industrial solvents, known locally as "Activo" or "Chemo", has risen in popularity among the homeless and among the street children of Mexico City in recent years. The mixture is poured onto a handkerchief and inhaled while held in one's fist.
In the US, Ether was used as a recreational drug during the 1930s Prohibition era, when alcohol was made illegal. Ether was either sniffed or drunk, and in some towns replaced alcohol entirely. However, the risk of death from excessive sedation or overdose is greater than that with alcohol, and ether drinking is associated with damage to the stomach and gastrointestinal tract. Use of glue, paint and gasoline became more common after the 1950s. Abuse of aerosol sprays became more common in the 1980s as older propellants such as CFCs were phased out and replaced by more environmentally friendly compounds such as propane and butane. Most inhalant solvents and gases are not regulated under illegal drug laws such as the United States' Controlled Substances Act. However, many US states and Canadian cities have placed restrictions on the sale of some solvent-containing products to minors, particularly for products widely associated with "sniffing", such as model cement. The practice of inhaling such substances is sometimes colloquially referred to as huffing, sniffing (or "glue-sniffing"), dusting, or chroming.
A 1983 survey of 4,165 secondary students in New South Wales showed that solvents and aerosols ranked just after analgesics (e.g., codeine pills) and alcohol for drugs that were abused. This 1983 study did not find any common usage patterns or social class factors. The causes of death for inhalant users in Australia included pneumonia, cardiac failure/arrest, aspiration of vomit, and burns. In 1985, there were 14 communities in Central Australia reporting young people sniffing. In July 1997, it was estimated that there were around 200 young people sniffing gasoline across 10 communities in Central Australia. Approximately 40 were classified as 'chronic' sniffers. There have been reports of young Aboriginal people sniffing gasoline in the urban areas around Darwin and Alice Springs. Substitution of gasoline by non-sniffable Opal fuel (which is much less likely to cause a "high") has made a difference in some communities.
A number of 1970s punk rock and 1980s hardcore punk songs refer to inhalant use. The Ramones, an influential early US punk band, referred to inhalant use in several of their songs. The song "Now I Want to Sniff Some Glue" describes adolescent ennui and the song "Carbona not Glue" states that "My brain is stuck from shooting glue". An influential punk fanzine about the subculture and music took its name ("Sniffin' Glue") from the Ramones song. The 1980s punk band Dead Milkmen wrote a song, "Life is Shit" from their album "Beelzebubba" about two friends hallucinating after sniffing glue. Pop punk band Sum 41 wrote a song "Fat Lip", which refers to a character who does not "... make sense from all the gas you be huffing..."
Inhalants are also referred to by bands from other genres, including several grunge bands--an early 1990s genre which was influenced by punk rock. The 1990s grunge band Nirvana, which was influenced by punk music, penned a song "Dumb", in which Kurt Cobain sings "my heart is broke/But I have some glue/ help me inhale /And mend it with you". L7, an all-female grunge band, penned a song entitled "Scrap" about a skinhead who inhales spray paint fumes until his mind "starts to gel". The Beck song "Fume" from his "Fresh Meat and Old Slabs" release is about inhaling nitrous oxide. Another Beck song, "Cold Ass Fashion," contains the line, "O.G. - Original Gluesniffer!" The band Primus's 1998 song "Lacquer Head" is about adolescents who use inhalants to get high. Hip hop performer Eminem wrote a song, "Bad Meets Evil" which refers to breathing "...ether in three lethal amounts" . "The Brian Jonestown Massacre" a retro-rock band from the 1990s has a song entitled "Hyperventilation" which is about sniffing model airplane cement.
A number of films have depicted or referred to the use of solvent inhalants. In the 1980 comedy film Airplane!, the character of McCroskey (played by Lloyd Bridges) refers to his inhalant use when he states that "I picked the wrong week to stop sniffing glue." In the 1996 film Citizen Ruth, the character Ruth, a homeless drifter, is depicted inhaling patio sealant from a paper bag in an alleyway. In the movie Love Liza, the main character, played by Philip Seymour Hoffman, develops an addiction to inhaling gasoline vapor. Harmony Korine's 1997 film Gummo depicts adolescent boys inhaling contact cement for a "high". Edet Belzberg's 2001 documentary Children Underground chronicles the lives of Romanian street children addicted to inhaling paint.
Films have also depicted the use of gas-based or aerosol inhalants. In the David Lynch film Blue Velvet, the bizarre and manipulative character played by Dennis Hopper uses a mask to inhale an unknown gas. In Little Shop of Horrors, Steve Martin's character dies from nitrous oxide inhalation. In The Cider House Rules, Michael Caine's character is addicted to inhaling ether vapours. In the film thirteen, the main character, a teen, uses a can of aerosol computer cleaner to get high. The 1999 independent film Boys Don't Cry depicts two young, low-income rural women inhaling aerosol computer cleaner (Canned Air). In the movie Shooter, Mark Wahlberg inhales nitrous oxide gas from a number of Whip-It! whipped cream canisters until he becomes unconscious. The film Fear and Loathing in Las Vegas describes how the two main characters inhale diethyl ether and Amyl Nitrite.