Demonstration of naturalistic methods for cocaine smoking by human volunteers.

Five, healthy, adult, male research volunteers participated in up to four daily laboratory sessions while residing on a Clinical Research Unit. Two subjects were tested twice. Fifty milligrams of cocaine base was smoked one, two or four times each session with a 14-min interval between doses. Two subjects smoked cocaine placed in 'smoke-free' cigarettes, while the remaining subjects smoked cocaine placed in a modified tobacco pipe. Significant and biologically relevant cocaine venous blood levels were engendered most consistently using the modified tobacco pipe. Large, transient increases in heart rate, blood pressure and self-reported 'stimulated' scores were observed during single dosing sessions. During multiple dose sessions, cardiovascular activity either increased, returning to near baseline levels between doses, or were sustained, while reported 'stimulated' scores peaked after the first dose and were lower following subsequent doses. Both cardiovascular and subjective effects were greater on the ascending limb than on the descending limb of the cocaine blood level curve suggesting acute tolerance. Although preliminary, these results demonstrate the usefulness of this relatively simple procedure requiring subjects to smoke in the manner they are accustomed, and suggest the importance of further research in this area.