As more people explore the medical benefits of cannabis, there’s a growing corresponding need to be clear about possible side effects and interactions with other medications. This is especially true for seniors.
CAMH, Canada’s largest mental health and addictions teaching hospital and research centre, points out: “Although adults aged 65 and older make up about 13% of Canada’s population, they consume 20 to 40% of all prescription drugs and 25% of all over-the-counter drugs.”
Seniors are more likely to take more than one medication at a time, putting them at risk of drug interactions that may cause new health challenges. As people age, they also become more sensitive to the effects of medications.
The chances of experiencing adverse effects using medical cannabis with other prescription and over-the-counter drugs increase when people self-medicate¬ – that is, when they use combinations of medications without consulting doctors, pharmacists or other qualified healthcare professionals about possible interactions.
A recent survey has found that only 37% of Canadians using cannabis for medical purposes have a medical document from a healthcare practitioner. In other words, they are self-medicating and not getting professional help, putting them at greater risk of drug interactions and side effects.
“It is essential for Canadians to have access to support from health care professionals to help them navigate medical cannabis safely and effectively,” says Max Monahan-Ellison, Medical Cannabis Canada board member and survey lead.
Known Cannabis Interactions with Other Medications
The March 2020 issue of the Canadian Medical Association Journal (CMAJ) offer an article on “Drug Interactions with Cannabinoids.” Cannabinoids are active ingredients found in cannabis. The journal warns that in some cases:
- Cannabinoids can affect levels of other drugs
- Smoking marijuana can increase the clearance of some drugs
- Additive effects can occur with other drugs
- There are potential “red flag” interactions
The actual descriptions of these issues are aimed at medical professions. To learn more about possible cannabis interactions with other drugs, most of us are better served to start with a resource such as WebMD, which breaks down its information into Major Interaction, Moderate Interaction and Minor Interaction.
Under Major Interaction, it covers, for example, sedative medications such as barbiturates: “Marijuana might cause sleepiness and drowsiness. Medications that cause sleepiness are called sedatives. Taking marijuana along with sedative medications might cause too much sleepiness.”
Under Moderate Interaction, one of the drugs it covers is the antidepressant fluoxetine (Prozac). It warns: “Taking marijuana with fluoxetine (Prozac) might cause you to feel irritated, nervous, jittery, and excited. Doctors call this hypomania.”
Or it points out: “Disulfiram (Antabuse) might interact with marijuana. Taking marijuana along with Disulfiram can cause agitation, trouble sleeping, and irritability.”
Under Minor Interaction, WebMD writes, “Using marijuana might increase the effects of warfarin (Coumadin). Smoking marijuana while taking warfarin (Coumadin) might increase the chance of bruising and bleeding.” Warfarin is used to treat blood clots.
Searching for Cannabis Interactions by Drug Name
Drugs.com, a massive resource on drug and health issues aimed at consumers and medical professionals, claims that a total 377 drugs are known to interact with cannabis. Twenty-four are major interactions and the rest are moderate interactions.
The site allows visitors to search for drugs by name to see if there are possible interactions, or to choose from a list most frequently checked interactions. Ibuprofen users, for example, will be happy to hear: “No interactions were found between cannabis and ibuprofen.” But the site adds a common caveat: “This does not necessarily mean no interactions exist. Always consult your healthcare provider.”
If you use Zoloft (sertraline) for depression, panic attacks, obsessive-compulsive disorder, post-traumatic stress disorder, social anxiety disorder (social phobia), and other conditions, the warning is that used with cannabis:
“[It] may increase side effects such as dizziness, drowsiness, confusion, and difficulty concentrating. Some people, especially the elderly, may also experience impairment in thinking, judgment, and motor coordination. You should avoid or limit the use of alcohol while being treated with these medications. Also avoid activities requiring mental alertness such as driving or operating hazardous machinery until you know how the medications affect you.”
CBD and Drug Interactions
Since CBD (cannabidiol), a compound found in cannabis and hemp, is often used to ease symptoms of anxiety, insomnia and chronic pain, it’s worth checking out Healthline’s page on CBD’s interactions with other medications.
It points out that while research so far has shown that CBD is generally safe with few side effects, it “does have the potential to interact with some medications. The concern has to do with how the body metabolizes certain substances.”
For example, cannabis interferes with CYP3A4, an enzyme that takes care of metabolizing about 60% of clinically prescribed medications. Not only might cannabis stop CYP3A4 from metabolizing drugs properly, the reverse may also be true: The enzyme can stop the body from metabolizing CBD correctly.
If your body is slow in metabolizing a medication, then you may have more of that medication in your system that is intended, possibly exaggerating its effects and triggering unwanted side effects.
CBD interactions and side effects to watch out for include:
- Changes in appetite
- Changes in weight
- Decreases in medication effectiveness
Always Consult Healthcare Professionals
It is good for people to arm themselves with the right information about possible interactions between cannabis and other prescription and over-the-counter medications. They can become more active participants in their own care and know what questions to ask doctors, pharmacists and other healthcare professionals.
But consulting with healthcare professionals is the key. Too much is at stake for people to self-medicate, combining different drugs and playing with doses.
If you come to a Shoppers Drug Mart retail location, one of our pharmacists would be happy to talk to you about possible interactions between cannabis and other medications, answering any questions you may have to ensure your combination of drugs is safe and effective.