MARIJUANA SMOKING - EFFECTS OF VARYING PUFF VOLUME AND BREATHHOLD DURATION

Two studies were conducted to quantify biological and behavioral effec ts resulting from exposure to controlled doses of marijuana smoke. In one study, puff volume (30, 60 and 90 mi) and in a second study, breat hhold duration (0, 10 and 20 sec) were systematically varied while hol ding constant other smoking topography parameters (number of puffs = 1 0, interpuff interval = 60 sec and inhalation volume = 25% of vital ca pacity). Each study also varied levels of Delta(9)-tetrahydro-cannabin ol marijuana cigarette content (1.75% and 3.55%). Regular marijuana us ers served as subjects (n = 7 in each experiment). Subjects smoked 10 puffs in each of six sessions; a seventh, nonsmoking session (all meas ures recorded at the same times as in active smoking sessions) served as a control. Variations in puff volume produced significant dose-rela ted changes in postsmoking plasma Delta(9)-tetrahydro-cannabinol level s, carbon monoxide boost and subjective effects (e.g., ''high''). In c ontrast, breathholding for 10 or 20 sec Versus 0 sec increased plasma Delta(9)-tetrahydro-cannabinol levels but not CO boost or subjective e ffects. Task performance measures were not reliably influenced by mari juana smoke exposure within the dosing ranges examined. These findings confirm the utility of the controlled smoking technology, support the notion that cumulative puff volume systematically influences biologic al exposure and subjective effects, but cast doubt on the common belie f that prolonged breathholding of marijuana smoke enhances classical s ubjective effects associated with its reinforcing value in humans.