Marijuana and CBD May Cause Adverse Drug Interactions, Research Shows

Although they're now widely used, medical cannabis and medicinal cannabidiol (CBD) may cause adverse interactions with certain prescription medications, recent research suggests. A 2020 review article published in the journal Medical Cannabis and Cannabinoids lists 57 prescription medications that are potentially impacted by the use of cannabinoids, whether those are taken medicinally or recreationally.

These findings should inform the way people choose to consume these therapeutic substances depending on what they've been prescribed.

Drug Interactions with Cannabinoids

As CBD and cannabis products become increasingly available, there's a higher likelihood of an unintended interaction, the researchers write, not just with prescriptions but potentially with other herbal remedies or over-the-counter medications. Even cigarette smoking could be an issue, they note, because it may change how cannabinoids are metabolized.

Symptoms of interactions can run the gamut, and the research suggests the most common may be:

• Dizziness
• Confusion
• Cardiac side effects like rapid heartbeat and high blood pressure
• Gastrointestinal problems
• Daytime sleepiness
• Respiratory issues

More Research Needed

CBD, in particular, has prompted a breadth of claims about its benefits, including improved sleep, lowered anxiety, better workout recovery, lower pain levels, and increased focus. These potential benefits have driven some initial research, but it’s still pretty early in the CBD era before it becomes a must-have for everyone, according to Jordan Tishler, MD, professor at Harvard Medical School and president of the Association of Cannabis Specialists.

“There's a lot of promise and excitement about CBD oil,” he says. “But we have a great deal of research ahead to go beyond anecdotal evidence and preliminary research. And in terms of issues like quality, it’s the Wild West out there right now, since it’s unregulated. But for those with issues that could be helped, CBD provides an option worth trying.”

One significant area of necessary research is why CBD, as well as medical marijuana, may work well for some people and not others. With that information, it would be easier to determine potential drug interactions and side effects.

But unlike medications that work on other systems in the body, such as the cardiovascular or respiratory system, it's tricky because the main mechanism involves the body's endocannabinoid system, which doesn't operate in a straightforward way. Instead, endocannabinoids, the cannabis-like molecules produced by the body, work to regulate the other systems to maintain bodily homeostasis.

Your Body on CBD

Tishler says a good analogy for how the endocannabinoid system works is to think of a car manufactured today, which contains a computer controlling nearly every operation, from fuel delivery to GPS to assessing tire pressure.

That automotive brain is constantly tracking each system and can make small adjustments for efficiency, and your endocannabinoid system does the same, Tishler says. Neurotransmitters are located throughout the body and provide check-in updates that are regulated continually.

“Endocannabinoid receptors are in every system, from your lungs, kidneys, and bone marrow to your immune response, reproductive health, and pain modulation,” he says. “It affects pretty much everything in the body you can name.”

Alternative Avenues for Research

Another research direction that's likely to be pursued in the near future is the efficacy of different formulations, both with medical marijuana and CBD. With the latter, for example, the breadth of products is stunning, from topical creams and tinctures to an inhalable form for vaping, food options like gummies, and even a CBD-infused water.

Although medical marijuana is more limited in format, it still comes in forms like pills, extracts, liquids, topicals, and dry leaves for smoking.

There is not yet sufficient evidence about what’s considered the most effective, but anecdotally, it seems that there is an individualized response. For example, a medical marijuana or CBD tincture may do nothing for you, while an extract works like a charm, but it could be the other way around for someone else.

To get even more granular, one brand may not provide any relief of symptoms, while another does, even though they could contain the same amount of active ingredients.

Talk to Your Doctor

While researchers determine the many paths to follow for these products, there is an action people who use them should take: Keep track of what's being used, when it's taken, and any potential effects.

That applies not just to CBD and medical marijuana, but also any type of remedy. There can be interactions with medicinal herbs, and some supplements like St. John's wort and goldenseal can be particularly problematic.

"You need to let your doctor know what you're taking, right down to vitamin formulations," says Abigail Schildcrout, MD, an internal medicine specialist who runs a consulting firm, Practical Medical Insights, for patients trying to get more effective medical care. "Keeping track of everything before an appointment and having that information available will not only save time, but could also show a pattern of reactions that indicates there may be issue."