"Next to ingesting a drug, the simplest was of receiving its effects is to inhale it in some form of gaseous or vaporous state. [...] The psychoactive effect of an inhaled drug is even faster than a drug delivered through intravenous injection" ( Levinthal, 50-51).
The act of administering a drug or combination of drugs by nasal or oral respiration. Also, the act of drawing air or other substances into the lungs. Nicotine in tobacco smoke enters the body by inhalation.
Exposure to contaminants in the ambient air occurs principally via inhalation. If they are in gaseous form (as opposed to being adsorbed onto particles), inhaled contaminants can enter the general circulation directly, without being processed in the liver first, as are contaminants that are absorbed from the gastrointestinal tract.