Effect of Marijuana on Respiratory Function - 2018 WSAAI update

This is a Twitter summary from the 2018 WSAAI meeting. This summary was compiled from the tweets posted by @MatthewBowdish, an allergist/immunologist, who attended the 2018 Western Society of Allergy, Asthma and Immunology (WSAAI) meeting. The tweets were labeled #WSAAI. The text was edited and modified by me.

Rohit Katial: The Effect of Marijuana on Respiratory Function. Used the abbreviation "MJ" for marijuana.

Medicinal use of MJ dates back 5000 years with referenced in the original Hebrew version of Exodus. Ancient Egyptians used MJ to treat glaucoma as well as general inflammation. MJ has been used by a variety of cultures (Chinese, Ancient Indians, Hindus, Ancient Greeks, Romans, Arabians) over human history.

MJ remains illegal under federal law in the US, but 20 states now permit the sale of MJ for medicinal use.

Currently, 2 FDA medications on market, dronabinol and nabilone, which are synthetic cannabinoids used to treat nausea or neuropathic pain.

Other drugs in clinical testing include cannabidiol or CBD for short for childhood seizures and nabiximols for cancer pain.

In 2012, Colorado became 1st state to legalize MJ for recreational use. As of 1/1/17, 21 states and the District of Columbia will have decriminalized MJ and eliminated prohibition for possession of small amount, while 8 states will have legalized use of MJ for adult recreation.

Epidemiology of drug use in the US: https://twitter.com/MatthewBowdish/status/955938067545649152

Daily or near-daily MJ use among adults is much lower than daily or near-daily alcohol or tobacco use.

THC levels in blood rise rapidly during smoking, vaporization provides similar effects as smoking while reducing exposure to the byproducts of combustion and possible carcinogens. Plasma doses after oral doses were low and irregular, indicating slow and erratic absorption. Most data on MJ pharmacokinetics based on older studies when MJ was much less potent.

Herbal cannabis smoke contains the same constituents as tobacco smoke, including carbon monoxide, bronchial irritants, tumor initiators (mutagens), tumor promoters, and carcinogens. Mainly due to the way cannabis joints are smoked, with deep and prolonged inhalation and no filter, cannabis has a higher combustion temperature than tobacco.

Pulmonary inflammatory effects of MJ smoking: https://twitter.com/MatthewBowdish/status/955941422930173952

THC & Host Defense: https://twitter.com/MatthewBowdish/status/955941782725967873

Immunologic sequelae of MJ smoking may contribute to epidemiologic report linking MJ use to opportunistic infections and respiratory tract cancer.

There is association of MJ smoking with chronic respiratory symptoms including cough, sputum production, wheeze and breathlessness. Summary of reports on the association of MJ smoking with respiratory symptoms: https://twitter.com/MatthewBowdish/status/955942889787342848

Habitual MJ smoking is NOT associated with COPD. MJ smoking is also not associated with macroscopic emphysema, but there is some association with air trapping. Also, no impact with the typical decrease in lung function that we see with ageing, at least compared with tobacco smoking. MJ and Lung Function: https://twitter.com/MatthewBowdish/status/955943721266114560

Lung biopsies from young MJ smokers show inflammation, metaplasia and cellular atypia in 40-80% Barsky et all JNCI 90:1198. But despite abnormal histology, case-control studies suggest no association between habitual MJ smoking and lung cancer - however, these are short duration studies.

Summary of MJ and lung function: https://twitter.com/MatthewBowdish/status/955944770240589825

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