Insufflation (Latin insufflatio "blowing on" or "into") is the practice of inhaling a substance. Insufflation has medical use as a route of administration for many respiratory drugs used to treat conditions in the lungs (e.g., asthma or emphysema) and paranasal sinus (e.g., allergy).
The technique is common for many recreational drugs and is also used for some entheogens. Nasal insufflation (snorting) is commonly used for many psychoactive drugs because it causes a much faster onset than orally and bioavailability is usually, but not always, higher than orally. This bioavailability occurs due to the quick absorption of molecules into the bloodstream through the soft tissue in the mucous membrane of the sinus cavity and portal circulation bypass. Some drugs have a higher rate of absorption, and are thus more effective in smaller doses, through this route. Prodrugs, drugs that are metabolized or activated by the liver (such as codeine), should not be insufflated, because they need to be metabolized by the liver to break down into the compounds that are active (drugs absorbed through the GI tract pass through the liver before entering the systemic circulation, where drugs which are insufflated are absorbed directly into the systemic circulation).
The intranasal route (administration through the nose) may allow certain drugs and other molecules to bypass the blood–brain barrier via diffusion through the olfactory epithelium and the perineural sheath or via retrograde axonal transport along olfactory and trigeminal nerves. This latter process probably implies endocytosis of the molecules. Using this route to the brain allows high concentrations of products in the olfactory bulb shortly after exposition and by diffusion to the entire brain. Therefore using this pathway allows a better bioavailability, assuming that the molecule has the right physico-chemical characteristics to get through the nose and the epithelial defences.
Inert, nontoxic gases, such as carbon dioxide, are often insufflated into a body cavity, in order to expand workroom, or reduce obstruction during minimally invasive or laparoscopic surgery.
In the 18th century, the tobacco smoke enema, an insufflation of tobacco smoke into the rectum, was a common method of reviving drowning victims.