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Safety and Adverse Reactions/High Risk Patients

The popular notion seems to be that marijuana is harmless and this notion is increasingly reinforced by the current trend for legalizing marijuana. However this trend also creates more opportunities for pharmacists to educate patients about the risks and benefits of marijuana on their health. While there are limited randomized controlled trials using marijuana, there are observational studies and case reports which allow a health care practitioner to begin to understand the adverse effects and safety issues that medical cannabis present.


The graph below shows the relative likelihood a patient will experience the adverse effect if taking cannabis versus those patients not taking cannabis. As with all drug therapy there are contraindications and relative contraindications to therapy. Patients with unstable cardiovascular disease and history of cardiac arrhythmia should consult a cardiologist, as cannabis is known to increase heart rate and alter blood pressure. While inhalation is known to have rapid effects on the heart, it is hemodynamic changes are also noted in the package insert for FDA synthetic oral cannabis products.



Some other possible effects include:

Blurred vision  Increased appetite
Changes in blood pressure Loss of appetite
Cognitive impairment Mood alterations
Constipation Panic 
Cough Sore throat
Dry eyes Vomiting
Fatigue Increased heart rate


For good overviews of adverse effects, see these articles:


Volkow ND, Baler RD, Compton WM, Weiss SR. Adverse health effects of marijuana useN Engl J Med. 2014;370(23):2219–2227. doi:10.1056/NEJMra1402309


Bridgeman MB, Abazia DT. Medicinal Cannabis: History, Pharmacology, And Implications for the Acute Care Setting. P T. 2017;42(3):180–188.


A comment on the risk of overdose to medical cannabis provided by the Centers for Disease Control and Prevention


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