Recent discoveries in pharmacokinetics of drugs of abuse

Controlled human dosing studies with drugs of abuse have revealed the impor tance of the chosen route of administration on the delivery of drugs to the bloodstream and to their site of action. Recently, the intranasal and smok ed routes have become favored by some populations for the administration of illicit drugs. Research studies with experienced heroin and cocaine users indicated that an intranasally administered drug generally provided lower b lood concentrations of drug and a slower onset of action compared to the in travenous route; however, intranasal doses are easily manipulated by the us er and adequate bioavailability and desired drug effects can be achieved. I n addition, the trauma of needle use is avoided and disease exposure is red uced by this route. For marijuana, the smoked route of administration has a lways been the preferred route. In recent studies with smoked marijuana, it was revealed that single puffs of marijuana smoke produced detectable bloo d concentrations of tetrahydrocannabinol, the active ingredient of marijuan a. Continued smoking produced rapid increases in blood concentrations with peak concentrations and effects occurring before or near the end of smoking , demonstrating the rapidity and efficacy of the smoking route for marijuan a. The smoked route has also become popular with cocaine and heroin users. This route provided equivalent peak blood concentrations and time of onset of drug effects as the intravenous route. In addition, arterial boli drug c oncentrations reaching the brain are likely to be higher following the smok ed route compared to the intravenous route. Overall, these studies demonstr ated that the smoked and intranasal routes are highly efficacious for the d elivery of illicit drugs and produce a similar profile of drug action to th e intravenous route of administration. (C) 1998 Elsevier Science Ireland Lt d. All rights reserved.