Using a CBD product? Be sure to tell your doctor

Cannabinoid products may interfere with some prescription medications, so people who use them should add these to the list of supplements they tell their doctors about.

This interference could have serious health consequences, according to Penn State Health, which offered some additional advice as legal medical and recreational cannabis becomes more common.

"Whether it's recreational cannabis, prescribed cannabinoid or medical marijuana, it's important your doctor knows you're using it," said Kent Vrana, head of the pharmacology department at Penn State College of Medicine.

"A problem in Pennsylvania is that you can get a medical marijuana card without any involvement by your [primary care physician], meaning your doctor may have no idea you're using if you don't say something," Vrana said in a college news release.

It's possible that over-the-counter cannabidiol, better known as CBD, could benefit millions of people because of its medicinal properties without the high feeling, Penn State Health said.

Recreational marijuana contains tetrahydrocannabinol (THC), which makes users high. THC is sometimes present in CBD products.

CBD has been proven safe and effective in the treatment of seizure disorders and may be useful for treating some cancers, Vrana said, but science on the substance is still limited.

Prescription CBD is considered safe when used as directed. But other marketed products, such as oils, lotions or gummies, may not be approved by the U.S. Food and Drug Administration. They can contain potentially harmful substances.

"The trouble is, the whole industry is not regulated by the FDA," Vrana said. "It's like the Wild West out there."

Vrana, together with Paul Kocis, a clinical pharmacist at Penn State Health Milton S. Hershey Medical Center, has researched the potential for interactions between the cannabinoids and prescription medications.

The researchers later worked with computer science students from Penn State Harrisburg to launch a web-based application to increase awareness of possible drug interactions. The CANNabinoid Drug Interaction Review (CANN-DIR.psu.edu) tool can be used by anyone.

It is available in 11 languages and is used in more than 80 countries.

"Our emphasis with this tool is on patient safety," Kocis said in the release. "There really was no information about how CBD and THC might affect other medications, so we set out to fill a need that was not being met."

Drugs with which cannabinoids can interact include certain antidepressants, anticonvulsants, sedatives and narcotics.

The blood thinner warfarin (Coumadin) is a common medication that can be affected by a cannabinoid. Marijuana might cause excessive bleeding in patients taking this medication.

"A lot of people aren't aware of these potential interactions and that's why we thought it was important to provide a tool like CANN-DIR, which can be easily used by both medical professionals and patients," Kocis said. "It's about enhancing safety for everyone."

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