As with any dietary supplement, it is important to understand that any ingested substance has the potential to interact with other medications. In the case of CBD, we know that CBD can affect the Cytochrome P450 enzyme system in the liver, and this has potential implications for people taking other medications.
The Cytochrome P450 (CYPs) enzymes are found in the body where they play a key role in breaking down various chemicals. While CYPs are found in virtually every cell in the body, the ones in the liver play an especially important role is metabolizing medications taken orally. The Human Genome Project has identified 57 different human genes that code for the various CYP enzymes.
As you are probably aware, all medications (prescription or over-the-counter) come with dosage instructions (for example, 2 tablets every four hours). Drugs taken orally aren’t effective for an unlimited amount of time because the CYP enzymes are responsible for metabolizing them (i.e. breaking them down). Research allows scientists to determine how long as particular medication is effective by studying its rate of breakdown. It’s important to follow the instructions that come with any medication to avoid the risk of overdose.
Some substances (like grapefruit juice) are known to inhibit the CYP enzymes. If these enzymes are inhibited, then they don’t break down medications at their normal rate. That means that a medication may be at an effective dose in the body for a longer-than-normal period of time. If a person were unaware of this fact and kept taking that medication at regular intervals, the medication could build up in the body and put that person at risk for overdose. This is why people are usually told to avoid eating grapefruit or drinking grapefruit juice while taking prescription medications.
CBD is metabolized primarily by CYP2C19 and CYP3A4 – although there is evidence that 7 of the 14 human CYP enzyme families may be involved in the breakdown of CBD. While CBD is being metabolized by these enzymes, the enzymes are unavailable for breaking down other medications. Therefore, CBD is said to inhibit or inactivate the CYP enzymes, particularly those of the 3A and 2C subfamilies.
The inhibition of the CYP3A4 enzyme by CBD is the most concerning, because it is the enzyme that breaks down the largest number of commonly used medical drugs. Therefore, you should consult your doctor to make sure that it is safe for you to use CBD.
CBD administered at a dose of 130 mg/kg (much higher than typical clinical doses) completely inactivated CYP2C and CYP3A enzymes, while repeated doses of 8-25 mg/kg per day showed a marked decline in the ability to CYP3A4 to metabolize its other substrates. There is also some evidence that long-term use of CBD could change the expression of gene expression of CYP enzymes, altering the level of these enzymes in the body.
The bottom line is that you should consult with a medical professional before supplementing with CBD. If you are worried about your CYP450 system, a physician can test the metabolism of any medications you take to make sure you are breaking them down as you should be.
You should also keep in mind that CBD’s strong anti-inflammatory potential comes from its ability to suppress the normal immune response. This suppression of immune activity could have potential negative consequences for your defenses against infectious agents like bacteria or viruses. But on the bright side, CBD does increase one part of the immune response – the number of natural killer cells – which help your body with its non-specific defenses and its surveillance against cancer cells.
The positive and negative consequences from CBD supplementation depend in large part on the dosage and frequency of CBD consumption. Always consult with your medical doctor about any questions you have about using CBD oil as part of your health and wellness plan.