EFFECTS OF CRACK COCAINE ON PULMONARY ALVEOLAR PERMEABILITY

Background: Lung clearance of Tc-99m-labeled diethylenetriamine pentaa cetate (DTPA) is a sensitive test of altered alveolar epithelial perme ability that has been found to be increased in smokers of tobacco, as well as a small number of healthy smokers of crack cocaine, suggesting the possibility of subclinical crack-related lung injury. Study objec tive: To evaluate further whether habitual smoking of cocaine alone al ters alveolar permeability, whether crack smoking adds to or potentiat es the effects of tobacco and/or marijuana, and whether experimental c ocaine smoking acutely alters DTPA lung clearance. Design: Observation al cohort study (habitual cocaine smoking) and single-blind crossover study (experimental cocaine administration). Subjects: Fourteen habitu al smokers of cocaine alone (CS), 19 smokers of cocaine and tobacco (C TS), 3 smokers of cocaine and marijuana, 12 smokers of cocaine, tobacc o, and marijuana (CMTS), and 5 smokers of marijuana plus tobacco (MTS) . Results obtained in the crack-smoking subjects were compared with da ta previously obtained in 10 nonsmokers (NS), 9 smokers of tobacco alo ne (TS), 10 smokers of marijuana alone (MS), and 4 additional MTS. Met hods: Subjects underwent measurements of DTPA radioaerosol lung cleara nce after refraining from marijuana and/or cocaine for > 12 h and from tobacco for > 2 h. Ten of the 48 crack users were tested on two days 1 to 2 weeks apart within 2 h of experimental smoking of three physiol ogically active or inactive doses (total 98.8 +/- 15.5 or 8.5 +/- 2.5 mg, respectively) of cocaine base. Lung clearance half-times (T1/2) we re computed from time-activity curves for each lung. Results: T1/2 val ues for each lung in CS and MS were comparable to those of NS, while T S, MTS, CTS, and CMTS had significantly shorter clearance rates than N S (p < 0.01; three-way analysis of variance). No additive or interacti ve effects on T1/2 were noted among tobacco, cocaine, and/or marijuana . No acute effect of experimental cocaine smoking on T1/2 was noted. C onclusion: Whereas regular smoking of tobacco alone or with other subs tances increases alveolar epithelial permeability, habitual smoking of cocaine and/or marijuana has no measurable effect on alveolar permeab ility in the absence of tobacco nor any additive effect to that of tob acco alone.