Marijuana and Health (1982) / Chapter Skim
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CHEMISTRY AND PHARMACOLOGY OF MARIJUANA
CHEMISTRY AND PHARMACOLOGY OF MARIJUANA
Pages 12-33
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From page 12... ...
. In the mid-l960s, the isolation and synthesis of the main psychoactive component of cannabis and related cannabinoids, together with a rapid increase in the use of marijuana by middle class North American students, stimulated scientific activity (Waller et al., l976; Waller et al., in press)
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A single cannabinoid, A-9-THC, produces almost all the characteristic specific pharmacological effects of the complex, crude cannabis mixtures. A number of synthetic cannabinoids have pharmacological effects similar to A-9-THC.
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l4 TABLE l Chemical Constituents of Cannabis Preparations l. Cannabinoids: 6l known a.
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Toxic substances, such as carbon monoxide, hydrogen cyanide, and nitrosamines occur in similar concentrations in tobacco and marijuana smoke; so do the amounts of the particulate material known collectively as "tars." It is not easy to compare the toxicity of a given number of marijuana cigarettes to a given number of tobacco cigarettes. There are general similarities in the composition of the smoke, but the variations in composition of both tobacco and marijuana cigarettes and differences in smoking techniques make simple extrapolations of risks of tobacco versus marijuana smoking not valid.
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£ Crude marijuana extract£ Illicit hashish oilS. Research harvests!
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Mainstream smoke I . Gas phase Carbon monoxide, vol.
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As with all cannabis preparations, the A-9-THC content of hashish varies enormously, but the upper limits of A-9-THC content are usually much higher than for marijuana: 7 percent or higher and even higher for hashish oil (Table 2)
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From page 19... ...
A readily available enzyme immunoassay will detect cannabis metabolites in the urine for as long as a week after the smoking of a single marijuana cigarette. Thus, a positive urine test by this method is not necessarily indicative of use within the previous few hours and does not provide evidence of recent intoxication as a breath test does for alcohol.
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. High blood levels fall rapidly for the first 30 minutes, as the A-9-THC distributes to tissues with high blood flow.
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Although smoking avoids many of the absorption problems discussed above, a host of other variables affecting dose are introduced, such as the size and packing of the cannabis cigarettes, the way the smoke is inhaled, the number of puffs and the interval between puffs, the temperature produced in the burning cigarette, and whether a cigarette is shared. Because of the progressive concentration of cannabis constituents in the cigarette butt, the last few puffs yield considerably more A-9-THC and particulate matter than do the earlier puffs.
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From page 22... ...
. Because only trace amounts of cannabinoid metabolites are present in urine of these passive inhalers, it is unlikely that the low levels of the absorbed cannabinoids from the ambient air account for the so-called "contact high." Experiencing subjective cannabis effects in the presence of cannabis smokers could be explained by psychologic factors in addition to any pharmacologic ones.
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From page 23... ...
There may be fairly rapid and complete metabolism of free A-9-THC followed by slow release and metabolism of sequestered A-9-THC and retained metabolites. Because no direct measurements of cannabinoid levels have been made in tissue samples from human cannabis users and the data are limited in experimental animals, one can only infer from blood levels what metabolites are accumulating and where.
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From page 24... ...
Marijuana cigarettes containing more than 20 mg of A-9-THC seem to be a large dose, and those with l0 mg produce effects generally considered the result of a small dose. When volunteers were allowed to select their own self-determined smoked doses in controlled experiments, some smoked only one or two 20-mg cigarettes daily, while other similar volunteers smoked six to ten or more cigarettes per day.
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From page 25... ...
Comparisons of A-9-THC blood levels in human beings and in several species suggest roughly similar intensity of effects at similar blood levels in the various species (Rosenkrantz and Fleishman, l979)
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. The spores pass easily through contaminated marijuana cigarettes and when smoked are presumed to enter the body.
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Drug interactions also can occur by means of functional mechanisms. These can be additive, resulting in enhancement or prolongation of behavioral and psychological effects by cannabis when combined with other central nervous system depressant drugs, such as alcohol and barbiturates.
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The long persistence of cannabinoid metabolites in the body may have delayed effects or health implications not yet recognized, because, even with relatively infrequent use, there is chronic exposure to biologically unknown materials. In this respect, cannabis differs fundamentally from such drugs as alcohol, nicotine, and caffeine, which are rapidly metabolized and eliminated from the entire body.
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' Characterization of the toxicological significance of common cannabis contaminants such as paraquat and other chemicals, fungi, and bacteria should be continued.
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XLIX. Gas chromatographic determination of hydrogen cyanide and cyanogen in tobacco smoke.
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From page 31... ...
and Leuchtenberger, R Cytological and cytochemical studies of the effects of fresh marihuana cigarette smoke on growth and DNA metabolism of human lung cultures, pp.
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From page 32... ...
In Report of an Addiction Research Foundation/World Health Organization (ARF/WHO) Scientific Meeting on Adverse Health of Behavioral Consequences of Marijuana Use.
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From page 33... ...
Marijuana intoxication by passive inhalation: Documentation by detection of urinary metabolites.
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