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Marijuana and Health (1982) / Chapter Skim
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EFFECTS OF MARIJUANA ON THE RESPIRATORY AND CARDIOVASCULAR SYSTEMS
Pages 57-79

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From page 57...
... Different effects would be expected from tobacco and marijuana smoking because of the striking differences in the way in which the two substances are smoked: marijuana smoke usually is drawn deeply into the lungs by one or a few deliberately deep breaths, whereas tobacco smoking is generally more automatic, repetitive, and variable in pattern. Moreover, because marijuana is a "street drug," it not only is inconsistent in its content but also is subject to contamination.
From page 58...
... . In contrast, heavy marijuana smoking, i.e., at least 4 days per week for 6 to 8 weeks did cause mild airway obstruction (Tashkin et al., l976)
From page 59...
... The clinical significance of these abnormalities is uncertain. The marijuana smoked and the impairment in pulmonary function, coupled with the observation that reversibility of function was incomplete l week after marijuana smoking had stopped, suggests that heavy marijuana smoking over a much longer period could lead to clinically significant and less readily reversible impairment of pulmonary function.
From page 60...
... , where marijuana usage is heavy, chronic bronchitis is frequent. However, marijuana smoking is usually associated with tobacco smoking, which confounds interpretation of the effects of marijuana alone.
From page 61...
... The study of a respiratory disease in hashish or marijuana smokers is difficult because the great majority also smoke tobacco cigarettes. Also, the illegality of marijuana smoking prevents people from volunteering information and cooperating in experimental studies.
From page 62...
... Carcinoma of the Lung The effect of marijuana as a carcinogen for lung, airways, and upper respiratory organs has not been systematically explored. Evaluating the carcinogenicity of marijuana is difficult, because most marijuana smokers also are tobacco cigarette smokers and because such carcinogenicity could have a long period of latency; studies of tobacco carcinogenesis indicate that 20 to 30 years of exposure must occur before tumors appear in the lung.
From page 63...
... . Exposure of human lung cells in culture to freshly generated marijuana smoke for up to 2 months resulted in increased mitotic indices, stimulation of ONA synthesis, and an increase in the population of cells with four times the DNA content of control cells or those exposed to tobacco smoke (Leuchtenberger et al., l973a,b)
From page 64...
... Summary: Respiratory System Lung Function and Defense Mechanisms The most important question about the effects of marijuana on the health of the respiratory system is whether acute or chronic marijuana smoking cause detectable structural or functional impairment of the lungs. Mild but measurable airway obstruction, affecting both large and small airways, can be shown to exist after 6 to 8 weeks of smoking marijuana daily, averaging five marijuana cigarettes a day; this decrement in function is reversible, but does not return to normal within one week of abstaining from smoking.
From page 65...
... No reliable data are available concerning the incidence of carcinoma of the lungs and upper respiratory passages in long-term users of cannabis. But a variety of experimental studies has sounded the alert that marijuana smoking -- just as tobacco smoking -- may be carcinogenic and that a combination of tobacco and marijuana smoke may have greater neoplastic potential than either one alone.
From page 66...
... . Human blood pressure usually increases moderately on acute administration of A-9-THC, but in monkeys and dogs acute administration is followed by a decrease in systemic arterial pressure.
From page 67...
... As the blood pressure falls, the heart rate slows from the high levels caused by initial marijuana administration. The decrease in blood pressure can be accentuated if the subject assumes an upright posture.
From page 68...
... to healthy young males elicits, in association with the increase in heart rate, changes in the ventricular contraction periods (an increase in ejection time and shortening of the preinjection period) , while systemic arterial pressure is unaffected (Weiss et al., l972; Kanakis et al., l976)
From page 69...
... . However, during chronic administration of A-9-THC, no change occurs in the reflex decrease in heart rate caused by infusion of a dose of the vasoconstrictor phenylephrine sufficient to increase the blood pressure (Benowitz and Jones, l975; Benowitz et al., l979)
From page 70...
... Also, in patients with coronary artery disease a large increase in heart rate can induce angina (pain) and even ischemic damage from insufficient oxygen as a result of an obstructed blood vessel.
From page 71...
... Although data are lacking on the magnitude of change in blood pressure caused by A-9-THC in hypertensives, it seems reasonable to assume that hypertensives smoking marijuana might have a greater increase in blood pressure than normals do. The increase in plasma volume and sodium retention that are associated with chronic exposure to A-9-THC could increase blood pressure in hypertensives and the mechanisms responsible for these changes very likely would interfere with the action of a number of antihypertensive medications.
From page 72...
... Evidence abounds that marijuana increases the work of the heart, usually by increasing heart rate, and in some persons by increasing blood pressure. This increase in workload poses a threat to patients with hypertension, cerebrovascular disease, and coronary atherosclerosis.
From page 73...
... Studies also are indicated to obtain new data about the effects of marijuana on: ' persons with hypertension, coronary artery disease, and cerebrovascular disease; * increases in systemic arterial pressure in low- and high-renin hypertension and the interactions between A-9-THC and several classes of antihypertensive medications; *
From page 74...
... and Bartova, A Effects of cannabinol derivatives on blood pressure, body weight, pituitary-adrenal function, and mitochondrial respiration in the rat, pp.
From page 75...
... Preservation of pulmonary function in regular, heavy, long-term marijuana smokers.
From page 76...
... Leuchtenberger, C., Leuchtengerger, R., Ritter, U., and Inui, N Effects of marijuana and tobacco smoke on DNA and chromosomal complement in human lung explants.
From page 77...
... Mechanism of increased specific airway conductance with marijuana smoking in healthy young men.
From page 78...
... Subacute effects of heavy marijuana smoking pulmonary function in healthy young males.
From page 79...
... The effects of smoked marijuana on metabolism and respiratory control.


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