Medical marijuana and its use by the immunocompromised

Those immunocompromised by AIDS or cancer chemotherapy use marijuana to allay symptoms of their disease or treatment. Some researchers believe that marijuana may further suppress the immune system. A list of immunological hazards that may be present in marijuana was collated and assessed, and clinical recommendations regarding the use of marijuana by immunocompromised individuals were made.

Databases and other sources from 1964 to 1996 were searched using keywords (e.g., cannabinoids, cannabis, hemp, marijuana). This was supplemented by a manual search of bibliographies, nonindexed books, and journals, and by consultation with experts. All reports were analyzed for antecedent sources. Data validity was assessed by source, identification methodology, and frequency of independent observations.

Substances implicated as potential immunological hazards in marijuana include endogenous constituents (cannabinoids, pyrolyzed gases, and particulates) and a longer list of exogenous contaminants, both natural (fungi and their metabolites) and synthetic (pesticides and adulterants).

Burning of marijuana creates toxins of combustion. Particulate toxins (tars) are reduced by the use of vaporizer apparati. Gas-phase toxins are filtered by water pipes, but water pipes also filter some tetrahydrocannabinol, making this strategy counterproductive. Viable fungal spores in marijuana pose the greatest hazard to immunocompromised patients, though they can be sterilized by several methods. Pesticide residues and other adulterants may be present in black-market marijuana, but are absent in sources of marijuana that are approved by the Food and Drug Administration.