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Who knows of good natural ways to control these respiratory symptoms?
Marijuana Use Linked to Bronchodilation and Respiratory Symptoms CME/CE
News Author: Laurie Barclay, MD
CME Author: Charles Vega, MD, FAAFP
Complete author affiliations and disclosures, and other CME information, are available at the end of this activity.
Release Date: February 20, 2007; Valid for credit through February 20, 2008
Credits Available
Physicians - maximum of 0.25 AMA PRA Category 1 Credit(s)™ for physicians;
Family Physicians - up to 0.25 AAFP Prescribed credit(s) for physicians;
Nurses - 0.25 nursing contact hours (None of these credits is in the area of pharmacology)
All other healthcare professionals completing continuing education credit for this activity will be issued a certificate of participation.
Physicians should only claim credit commensurate with the extent of their participation in the activity.
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February 20, 2007 — Short-term exposure to marijuana was linked to bronchodilation and long-term use increased respiratory symptoms suggestive of obstructive lung disease, such as cough and sputum production, according to the results of a review study reported in the February 12 issue of the Archives of Internal Medicine.
"The relationship between marijuana smoking and pulmonary function or respiratory complications is poorly understood; therefore, we conducted a systematic review of the impact of marijuana smoking on pulmonary function and respiratory complications," write Jeanette M. Tetrault, MD, of the West Haven Veterans Affairs Medical Center in West Haven, Connecticut, and colleagues. "Tobacco smoking is associated with numerous adverse pulmonary clinical outcomes, affecting both pulmonary function and respiratory complications."
Using the MEDLINE, PsychINFO, and EMBASE databases from January 1, 1966, to October 28, 2005, the investigators selected 34 studies meeting predefined criteria that evaluated the effect of marijuana smoking on pulmonary function and respiratory complications. Based on established criteria, 2 independent reviewers extracted data and evaluated study quality. Study results were critically appraised for clinical relevance and research methods.
Eleven of 12 challenge studies, which examined the association between short-term marijuana use and airway response, showed an association between short-term marijuana administration and bronchodilation (eg, increases of 0.15 - 0.25 L in forced expiratory volume in 1 second). There was no consistent association demonstrated between long-term marijuana smoking and measures of airflow obstruction.
All 14 studies that evaluated long-term marijuana smoking and respiratory complications noted an association with increased respiratory symptoms, including cough, phlegm, and wheeze (for cough, odds ratio, 2.00; 95% confidence interval, 1.32 - 3.01). However, the studies varied in their overall quality, including controlling for confounders such as tobacco smoking.
"Short-term exposure to marijuana is associated with bronchodilation," the authors write. "Physiologic data were inconclusive regarding an association between long-term marijuana smoking and airflow obstruction measures. Long-term marijuana smoking is associated with increased respiratory symptoms suggestive of obstructive lung disease."
Study limitations are that these findings do not directly apply to pulmonary administration of tetrahydrocannabinol via specialized delivery systems, methodologic limitations in the individual studies, lack of standardization of outcome measurements, and possible failure to identify all possible studies examining these relationships.
"Despite these limitations, this review should alert primary care physicians to the potential adverse health outcomes associated with the widespread use and abuse of and dependence on marijuana," the authors conclude. "Large prospective studies should be designed that carefully account for potential confounding factors (including detailed assessments of tobacco, substance abuse, and occupational and environmental exposures) that can affect lung health.... On the basis of currently available information, health care professionals should consider marijuana smoking in their patients who present with respiratory complications and advise their patients regarding the potential impact of this behavior on their health."
The Program of Research Integrating Substance Use in Mainstream Healthcare (PRISM), the Robert Wood Johnson Foundation, the National Institute on Drug Abuse (NIDA), and the National Institute on Alcohol Abuse and Alcoholism supported this study. Some of the authors have disclosed various financial relationships with the Veterans Affairs Office of Academic Affiliations, the Yale Mentored Clinical Scholar Program, the NIDA, the American Heart Association, the Association of Subspecialty Professors, CHEST Foundation of the American College of Chest Physicians, T. Franklin Williams Geriatric Development Research Award, K23 Mentored Patient-Oriented Career Development Award, and/or Robert Wood Johnson Foundation.
Arch Intern Med. 2007;167:221-228.
Learning Objectives for This Educational Activity
Upon completion of this activity, participants will be able to:
a.. Describe the relationship between marijuana smoking and the risk for lung cancer.
b.. Identify pulmonary complications related to marijuana smoking.
Clinical Context
While an estimated 14.6 million Americans older than 12 years use marijuana illicitly, many of the long-term health consequences of this habit are largely unknown. A previous review by Mehra and colleagues, which was published in the July 10, 2006, issue of the Archives of Internal Medicine, demonstrated that marijuana smoking was associated with increased tar exposure, increased oxidative stress, and bronchial mucosal histopathologic abnormalities compared with tobacco smokers or nonsmoking controls. However, the authors could not find a significant association between marijuana smoking and the risk for lung cancer after adjusting for the confounding use of tobacco.
Marijuana has also been associated with pulmonary symptoms, although studies investigating this issue have been heterogeneous in terms of their methodology. The current systematic review attempts to find conclusions based on the data from collected studies of the use of marijuana.
Study Highlights
a.. The study authors reviewed MEDLINE, PsychINFO, and EMBASE databases for reports of respiratory complications or pulmonary function related to marijuana smoking among adults. Studies published between 1966 and 2005 were included in the review, and all studies had at least 10 subjects.
b.. 2 reviewers evaluated study quality. The research was heterogeneous enough to disallow a meta-analysis, so the authors performed a qualitative synthesis of study data.
c.. 965 studies were identified on initial analysis, of which 34 qualified for inclusion in the current review. 12 studies used a laboratory-challenge design to determine the acute effects of marijuana smoking on pulmonary function, while 15 cross-sectional, 3 observational cohort, 3 case series, and 1 case-control study examined the long-term effects of marijuana smoking.
d.. Marijuana smoking reduced measures of airway resistance in all but one study. This effect peaked at 15 minutes and lasted up to 1 hour. Forced expiratory volume in 1 second increased by a mean of 0.15 to 0.25 L from baseline after smoking marijuana. Marijuana also reversed methacholine-induced and exercise-induced bronchospasm in 1 study.
e.. 1 study that focused on exposure to marijuana for a duration of 47 to 59 days found an increase in airway resistance at the end of the study period.
f.. Generally, airway obstruction was slightly increased with more chronic use of marijuana, although these results were not always statistically significant when adjusted for tobacco use. There were inconsistent results for the diffusing capacity of the lung for carbon monoxide among chronic marijuana users.
g.. All 14 studies examining respiratory complications found a positive relationship between these outcomes and marijuana smoking. Complications included cough, sputum production, and wheeze. This effect was dose-dependent in one study and appeared similar to the risk for respiratory symptoms associated with tobacco smoking in another study.
h.. Marijuana smoking was also associated with increased risks for bronchitis, dyspnea, hoarseness, and worsened asthma symptoms.
i.. The 3 observational cohort studies had the strongest methodology of all the research reviewed. In only one of these studies, marijuana was found to independently harm pulmonary function.
Pearls for Practice
a.. A previous review of the medical literature found that marijuana may increase markers related to an increased risk for lung cancer, but it did not independently increase the risk for lung cancer itself.
b.. The current review suggests that marijuana smoking promotes acute bronchodilation but also increases cough, wheeze, and sputum production in the long term. There were conflicting reports regarding the long-term effects of smoking marijuana on pulmonary function.
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