CBD and Medication Interactions: A Primer for Safe Use
DOES CBD REACT WITH OTHER MEDICATIONS?
When we take any medication or substance, our bodies have a system in place to move the substance safely out. First, the liver adds an oxygen molecule to the chemical, which makes it more water soluble. Then the kidneys can flush the chemical out of our system. It’s a very efficient way to keep our blood clean and remove toxins. The liver adds that oxygen molecule using an enzyme that is part of the system called cytochrome P-450.
The liver makes the cytochrome P-450 enzymes when it is healthy. A liver that is struggling may have difficulty is doing its job of cleaning the chemicals out of our system. Some drugs put a strain on that enzyme system. Others act as an inhibitor, and either use up all the available enzymes, or shut down production. CBD acts as a potent competitive inhibitor of cytochrome P-450 enzymes.
What this means in practical terms is that the drugs that we take aren’t removed from the blood stream the way we expect them to be when we are using CBD. Modern medication dosing is based on the understanding that a normal liver will get rid of the drug in so many hours. The dosing is based on that healthy liver and healthy cytochrome P-450. That’s why some medications have to be taken twice a day, for example- the liver has cleaned them out quickly. When the production of the enzymes are inhibited, the drugs stay in the system longer. The levels of the drug may get too high.
Most of the time, this does not present a problem. Medication dosing can be taken at a different time of day than the CBD, for instance. But for some drugs, the dosing and the amount of the drug in the system is critical to the medication working properly. Drugs that can accumulate to dangerous levels are of particular concern when taken with CBD. These are anti-seizure medications and warfarin. The recommendation is to take a standardized dose of CBD at the same time daily, and have both the drug levels of the medication and liver enzyme levels checked to ensure safety.
Some heart medications used for arrhythmias and blood pressure may also build up higher levels in the blood when taken with CBD. Your doctor may suggest lowering the dose of medications after doing home blood pressure monitoring, or may just recommend doing blood pressure monitoring at home to make sure no side effects are occurring. For anyone taking CBD and any blood pressure or heart medication, taking the blood pressure daily, at the same time, and bringing that log into the doctor’s office is a practical safety measure.
Antidepressant, antipsychotics, and benzodiazepine anxiety medications are mostly metabolized by cytochrome P-450. The levels of these drugs can get too high when CBD is on board. It is important to notice any side effects of too high a dose, particularly lightheadedness or falling. But these are not drugs a person should take themselves off of without medical supervision. If a person wants to move from prescription drugs for mental health to holistic treatments for anxiety, which can include CBD, the transition must be done under medical supervision. There can be life-threatening consequences of stopping these medications too rapidly.
For more information on safe drug interactions with CBD and cytochrome P-450 inhibitors, Project CBD has an excellent introductory article on the kinetics of CBD. The Flockhart Table is a complete list of drugs metabolized by cytochrome P-450.