Inhalation studies with drugs of abuse.

In recent years, smoking or inhalation of drugs has become a popular route of administration among drug users. Various drugs of different classes have been abused by inhalation or smoking, including phencyclidine (PCP), cocaine, heroin, methamphetamine, and marijuana. This increased popu-larity of smoking drugs has resulted from the fast onset of drug action and fears related to contracting acquired immunodeficiency syndrome (AIDS) or other infectious diseases from intravenous (IV) injections. In particular, heroin smoking has increased dramatically; approximately 74 percent of the heroin addicts in India use this method of administration, and it is also popular in the United States (Griffiths et al. 1994). The shift toward smoking heroin has also been associated with an increased availability of illicit heroin on the streets, which has declined in price and increased in purity (Huizer 1987). Consequently, there is an increased risk of overdose.