No doubt there’s a lot of buzz surrounding the potential benefits of medical marijuana. Most recently, emerging research suggests it may be a safer yet still helpfully potent substitute for opioids to treat pain — though more study is needed.
But just as research continues into the possible benefits of using marijuana for treatment, questions remain about how cannabis might interact with prescribed or over-the-counter medications a person may also be taking.
Though some states have legalized the use of marijuana for medical purposes, as well as for recreation to varying degrees, the federal government has not. “Part of the challenge with understanding how marijuana interacts with other products — either prescribed or over the counter — is that there’s such tight restrictions on the way marijuana is scheduled” by the Drug Enforcement Administration, says Dr. Timothy Brennan, an addiction medicine physician and director of the Addiction institute at Mount Sinai West and Mount Sinai St. Luke’s hospitals in New York City. So even while many people may use marijuana, tight federal restrictions limit researchers’ ability to study cannabis as approved medications are typically studied, including evaluating whether it can safely be taken with medications.
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“There’s not a lot of research in this area,” says Dr. Greg Carter, a clinical professor of biomedical sciences at the Elson S. Floyd College of Medicine at Washington State University in Spokane. Carter has done research in the area of medical uses of cannabis for more than 20 years.
Marijuana use for medical purposes and recreation is legal in Washington.
In addition to researching medical marijuana, Carter recommends it to some patients to treat issues like pain. “I go through all the potential side effects, and what the expected effects are of the cannabis. I treat it just like any other drug,” he notes. “And I would say in 20 years of doing this, I haven’t had any significant drug-drug interactions.”
But that’s not to say marijuana couldn’t interact harmfully with other drugs — or lessen a medication’s effectiveness.
“I think for any other drug that is potentially sedating or has some of the same effects as cannabis, it can enhance those effects. That’s not necessarily a drug-drug interaction in the way physicians think of it, but it can enhance the central nervous system depressing effect of other medications,” Carter says. “So if a patient comes to me and they’re on something like Valium, I would try to get them off of Valium if I was going to recommend cannabis.”
Experts emphasize that anyone using marijuana — for medical or recreational purposes — should discuss not only any potential health concerns but possible drug-drug interactions, too with his or her health provider. Sarah Melton, a clinical pharmacist and professor of pharmacy practice at East Tennessee State University, says it’s a good idea to talk to the pharmacist about that as well.
A psychiatric pharmacist, Melton fills prescriptions for patients taking a number of drugs, from antidepressants to benzodiazepines, that produce effects which she says may be altered by marijuana use. Though specific marijuana-medication interactions haven’t been studied, she says they can be theorized based on how the body processes, or metabolizes, marijuana along with how medications are metabolized. This includes the psychoactive ingredient THC and what’s called cannabidiol, or CBD, found in cannabis, though not in synthetic medications that contain only THC, such as dronabinol and nabilone.
Marijuana use isn’t legal in Tennessee. “We don’t really have medical marijuana quite yet, except for the CBD oil for seizures, but I’d say 50 percent of my patients that have mental health issues smoke marijuana every day,” Melton says. “So it’s really important for me to ask about that.” She talks about this routinely with those filling prescriptions, just as she asks about whether they smoke cigarettes or drink alcohol.
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Melton says one example of medicine that could interact dangerously with marijuana is benzodiazepines — like Valium or Xanax or Klonapin; a class of drugs primarily used to treat anxiety, these can be prescribed for other things as well like managing insomnia. CBD in marijuana (or CBD oil) can inhibit an enzyme the liver uses to metabolize medicine like benzodiazepines, she says, so that levels of the medication in the body go up. “So [that] can actually increase the blood levels of those benzodiazepines and cause more sedation” and even lead to problems like overdosing on the medication, Melton says.
CBD can slow down metabolization of cholesterol medications like Lipitor, too, Melton says, adding that’s important because some people have bad reactions to cholesterol medicines like pain in their muscles. “So that could actually make those reactions worse,” she says.
Conversely, she says marijuana use may reduce the effectiveness of other medications including antidepressants like Cymbalta, or duloxetine. “What I’ve noticed just in clinical practice — and there’s no data out there that says this is true yet, because nobody’s done the studies — but I have noticed that patients that smoke a lot of marijuana and that are on something like Cymbalta, they need higher doses to really get a good effect; and that’s because the marijuana is speeding up the metabolism of that antidepressant,” Melton says. That’s in addition to worries about marijuana’s psychoactive effects compounding mental health issues, she notes, as well as other health concerns.
The dearth of data on marijuana-medication interactions certainly concerns Brennan. “There really haven’t been any rigorous studies out there that allow us to weigh in one way or the other on the way cannabis interacts with other product,” he says.
On the other hand, many patients find relief using the marijuana in medical settings.
“In my patient population, I’ve had good success getting people on lower doses and sometimes off opioids completely with the use of medicinal cannabis,” Carter says; and there are other uses for medical marijuana, too. “Cannabis can help relieve pain. It can also relax muscles, help with sleep, improve appetite, reduce inflammation,” he says. “So it does a lot of things that opioids don’t do. Plus, it’s safer. You cannot overdose on cannabis.”
[See: 4 Opioid Drugs Parents Should Have on Their Radar.]
Taking into account both the potential promise of marijuana to treat what ails, and the limitations of cannabis research to date — including in regards to possible drug-drug interactions — experts agree on at least one thing: To reduce the chances of a potentially harmful marijuana-medication interaction, patients should disclose to their health providers if they’re using marijuana (if that provider didn’t recommend it, or doesn’t already know they’re using marijuana). “Make sure their health care provider knows they’re using cannabis,” Carter says. “That’s most important thing.”
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How Does Marijuana Interact With Medications? originally appeared on usnews.com
