Administration
For a substance to be psychoactive, it must cross the blood–brain barrier so it can affect neurochemical function. Psychoactive drugs are administered in several different ways. In medicine, most psychiatric drugs, such as fluoxetine, quetiapine, and lorazepam are ingested orally in tablet or capsule form. However, certain medical psychoactives are administered via inhalation, injection, or rectal suppository/enema. Recreational drugs can be administered in several additional ways that are not common in medicine. Certain drugs, such as alcohol and caffeine, are ingested in beverage form; nicotine and cannabis are often smoked; peyote and psilocybin mushrooms are ingested in botanical form or dried; and certain crystalline drugs such as cocaine and methamphetamines are often insufflated (inhaled or "snorted"). The efficiency of each method of administration varies from drug to drug.
Read more about this topic: Psychoactive Drug