Entourage Effects: Cannabis & Other Medications
For seniors and adults, perhaps the most important thing to understand about medical cannabis is that it’s very safe. While the psychoactive effects (present in cannabis that is rich in THC, but absent in CBD extracts) can be intense for someone not acclimated to them, deaths due to that drug alone do not happen. A person would have to consume the equivalent of one-third of their own bodyweight of cannabis for the dose to be lethal; this is about 50,000 times more than what it takes for intoxication. 
Still, cannabis does have a range of physiological effects, and seniors and adults considering this option should be aware of the way this substance can interact with other pharmaceutical or non-pharmaceutical drugs. Both the psychoactive, THC-rich strains or extracts and CBD can influence how other drugs in the body work, and vice-versa. This combination of cannabis with other drugs—known as an “entourage effect”—can be harmful, so if you’re taking prescribed medications or other substances, you should inform your doctor that you’re trying this kind of medicine. Furthermore, when you see a cannabis medical professional, have a list of what you’re currently taking on hand.
Though there are individual differences, there are a number of well-known interactions to be mindful of, including:
Blood Pressure Medications: For high blood pressure, your doctor may prescribe medications like beta blockers or diuretics to manage the condition. Some studies have noted that THC has been linked with short-term spikes in blood pressure—an effect that reduces as tolerance grows—while others found that, especially if you factor in other chemicals in the cannabis plant, the long-term effects may actually lower it.  Monitor your blood pressure levels carefully and talk to your PCP or cannabis provider if you’re seeing changes.
Opioids: A growing body of evidence suggests that use of cannabis can reduce the amount needed of opioid painkillers.  Given the dangerous and potentially lethal side-effects of opioids, this is very promising. Again, it’s important to keep your PCP and cannabis provider informed on what you’re taking.
Alcohol: Cannabis and alcohol taken together can significantly increase the level of intoxication. As such, especially in the early going, it’s a good idea to abstain from that glass of wine when taking cannabis.
Warfarin: This blood-thinning medication is prescribed to prevent blood clots. Cannabis slows down metabolism of this drug, leaving it in the system for longer. This can increase the amount of time it takes for blood to clot and can lead to bruising and internal bleeding. If you’re trying cannabis, make sure your INR levels are carefully monitored.
CBD & Drugs: CBD can affect liver metabolism, which influences the efficacy of a range of drugs, including some antibiotics, some antihypertensives, benzodiazepines, certain immunosuppressants, antihistamines, and some antipsychotics among many others.  Make sure to keep your PCP and cannabis provider in the loop.
Ultimately, it’s a good idea to treat cannabis as you would any other pharmaceutical and non-pharmaceutical drug. In the same way that you’d want to be careful when starting to take a new medication, care needs to be taken when incorporating cannabis into your own wellness regimen.
Schaffer Library of Drug Policy. Estimated Lethal Dose of Cannabis. Retrieved 24 January 2020, from http://druglibrary.org/schaffer/library/mj_overdose.htm
Bujara, S. (2018). Nonpsychotic Cannabinoids in Hypertension: Benefits and Harms – The Cardiology Advisor. Retrieved 24 January 2020, from https://www.thecardiologyadvisor.com/home/topics/hypertension/nonpsychotic-cannabinoids-in-hypertension-benefits-and-harms/
Grinspoon, P. (2018). Access to medical marijuana reduces opioid prescriptions – Harvard Health Blog. Retrieved 24 January 2020, from https://www.health.harvard.edu/blog/access-to-medical-marijuana-reduces-opioid-prescriptions-2018050914509
Chang, B. (2018). Cannabidiol and Serum Antiepileptic Drug Levels: The ABCs of CBD with AEDs. Epilepsy Currents, 18(1), 33-34. doi: 10.5698/1535-75220.127.116.11
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