Effects of varying marijuana smoking profile on deposition of tar and absorption of CO and delta-9-THC

Abstract

We investigated the effects of previously observed differences in smoking technique for marijuana (M) versus tobacco (T) on the amount of inhaled tar, the percentage retention of inhaled tar in the lung, the pre- to postcigarette boost in blood carboxy-hemoglobin (COHb) and in serum delta-9-tetrahydrocannabinol (THC concentrations), and psychophysiologic responses to THC (increased heart rate and subjective “high”). Ten healthy, habitual smokers of M were studied on 6 separate days. On each day, subjects smoked a single M cigarette (∼900 mg, 1.24% delta-9-THC) using one of 6 different smoking profiles typical for marijuana [puff volume (PV) ∼70 ml; breathholding time, (BHT) 14–16s] or tobacco (PV ∼ ml; BHT 4–5 s) or a combination of the two techniques (PV ∼70 ml and BHT 4–5 s; or PV ∼45 ml and BHT 14–16s). Inhaled volume (1.5 liters), interpuff interval (30 s) and number of puffs (6) were all fixed, except that for the ∼45-ml PV condition, the number of puffs was increased to 10 in 2 additional sessions to standardize the total amount of cigarette consumed to that of the ∼70 ml PV condition. The longer BHT significantly increased both percent retention of tar in the lung and the pre- to postsmoking rise in blood COHb, serum THC and heart rate, independent of puff volume and number. In contrast, the larger PV had no significant influence on these variables for the same amount of cigarette consumed. The longer BHT (and not the larger PV) characteristics of M smoking contributes to the greater COHb boost and lung retention of inhaled tar during M compared to T smoking. In addition, the longer BHT appears to enhance THC absorption.