Penn State researchers have developed an online resource to improve patient safety and help health care providers reduce the number of unintended interactions between marijuana and prescribed medications.

Called the CANNabinoid Drug Interaction Review (CANN-DIR), the free resource at was developed at the Penn State College of Medicine, an approved medical marijuana academic clinical research center.

The web application assesses cannabinoid products such as THC, CBD — or combination — against a database of prescription and over-the-counter medications.

“The adverse effects are not just limited to drowsiness,” Paul Kocis, a clinical pharmacist at Penn State Health Milton S. Hershey Medical Center, said of the interactions with cannabinoids.

The application is not intended to be diagnostic.

Users can select the cannabinoid product and other medications a patient is taking, then CANN-DIR provides information on whether the THC or CBD could affect the way prescribed drugs are metabolized.

Take Warfarin, for example.

Warfarin is an anticoagulant used to treat and prevent blood clots. Cannabinoid products could impact how the body metabolizes Warfarin. A small difference in the active ingredient could reduce its effectiveness or lead to an adverse event, such as bleeding.

“Turns out a lot can happen,” said Kent Vrana, project leader and professor and chair of the Department of Pharmacology.

Vrana added, “It’ll tell you if there’s a potential problem.”

Officials believe that this web application could be an important resource to those using marijuana for recreational or medicinal purposes.

Pennsylvania legalized medical marijuana in 2016, which became available to patients two years later for more than a dozen ailments. More than 740,000 patients and caregivers are registered in the state’s Medical Marijuana Program, according to information presented at the March 22 Medical Marijuana Advisory Board meeting.

“I don’t know that there is any similar app on the market,” said Hyuntae Na, an assistant professor at the School of Science, Engineering and Technology, who oversaw the Penn State seniors that worked on the project last spring.

Another group of computer science students are working on an updated version intended to be more user friendly for patients and caregivers.