Inhalants are a broad range of household and industrial chemicals whose volatile vapors or pressurized gases can be concentrated and breathed in via the nose or mouth to produce intoxication (called “getting high” in slang), in a manner not intended by the manufacturer. They are inhaled at room temperature through volatilization (in the case of gasoline or acetone) or from a pressurized container (e.g., nitrous oxide or butane), and do not include drugs that are sniffed after burning or heating. For example, amyl nitrite (poppers), nitrous oxide and toluene – a solvent widely used in contact cement, permanent markers, and certain types of glue – are considered inhalants, but smoking tobacco, cannabis, and crack are not, even though these drugs are inhaled as smoke.
Inhalants can be classified by the intended function. Most inhalant drugs that are used non-medically are ingredients in household or industrial chemical products that are not intended to be concentrated and inhaled. A small number of recreational inhalant drugs are pharmaceutical products that are used illicitly.
Another way to categorize inhalants is by their product category. There are three main product categories: solvents; gases; and medical drugs which are used illicitly.
Several medical anesthetics are used as recreational drugs, including diethyl ether (a drug that is no longer used medically, due to its high flammability and the development of safer alternatives) and nitrous oxide, which is widely used in the 2010s by dentists as an anti-anxiety drug during dental procedures. Diethyl ether has a long history of use as a recreational drug. The effects of ether intoxication are similar to those of alcohol intoxication but more potent. Also, due to NMDA antagonism, the user may experience all the psychedelic effects present in classical dissociatives such as ketamine in forms of thought loops and feeling of mind being disconnected from one’s body. Nitrous oxide is a dental anesthetic that is used as a recreational drug, either by users who have access to medical-grade gas canisters (e.g., dental hygienists or dentists) or by using the gas contained in whipped cream aerosol containers. Nitrous oxide inhalation can cause pain relief, depersonalization, derealisation, dizziness, euphoria, and some sound distortion.
Classification by effect
It is also possible to classify inhalants by the effect they have on the body. Some solvents act as depressants, causing users to feel relaxed or drowsy. Many inhalants act primarily as asphyxiant gases, with their primary effect due to oxygen deprivation. Nitrous oxide can be categorized as a dissociative drug, as it can cause visual and auditory hallucinations. Other agents may have more direct effects at receptors, as inhalants exhibit a variety of mechanisms of action. The mechanisms of action of many non-medical inhalants have not been well elucidated. Anesthetic gases used for surgery, such as nitrous oxide or enflurane, are believed to induce anesthesia primarily by acting as NMDA receptor antagonists, open-channel blockers that bind to the inside of the calcium channels on the outer surface of the neuron and provide high levels of NMDA receptor blockade for a short period of time.
This makes inhaled anesthetic gases different from 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 anesthetic gases but can also make them more dangerous than other drugs used for this purpose.