Cannabidiol is a safe, non-intoxicating, and non-addictive cannabis compound with significant therapeutic attributes, but CBD-drug interactions may be problematic in some cases.Cannabidiol is a safe, non-intoxicating, and non-addictive cannabis compound with significant therapeutic attributes, but CBD-drug interactions may be problematic in some cases.
With cannabidiol (CBD) poised to become widely available in pharmaceutical, nutraceutical, and herbal preparations, medical scientists are taking a closer look at CBD-drug interactions.
CBD and other plant cannabinoids can potentially interact with many pharmaceuticals by inhibiting the activity of cytochrome P450, a family of liver enzymes. This key enzyme group metabolizes most of the drugs we consume, including more than 60 percent of marketed meds.
At sufficient dosages, CBD will temporarily deactivate cytochrome P450 enzymes, thereby altering how we metabolize a wide range of compounds, including tetrahydrocannabinol (THC), which causes the high that cannabis is famous for.
THC metabolites contribute significantly to the effects of cannabis consumption. Eleven-hydroxy-THC (11-OH-THC), for example, is a THC metabolite that activates the CB1 cannabinoid receptor in the brain and induces a high more potently than THC itself. This means that the body’s metabolism of THC can make it more potent.
Different routes of cannabinoid administration have different effects. Inhaled THC enters capillaries in the lungs, passes into general circulation through the pulmonary arteries, and quickly crosses the blood-brain barrier. When ingested orally, however, THC is absorbed in the small intestine and then carried to the liver, where it is metabolized by subclasses of cytochrome P450 (abbreviated CYP), specifically the CYP2C and CYP3A enzymes.
These liver enzymes also metabolize CBD, converting it into 7-OH-CBD and 6-OH-CBD. But there has been relatively little research into the properties of these CBD metabolites.
The way CBD interacts with cytochrome P450 is pivotal; in essence, they deactivate each other. Preclinical research shows that CBD is metabolized by cytochrome P450 enzymes while functioning as a “competitive inhibitor” of the same liver enzymes. By occupying the site of enzymatic activity, CBD displaces its chemical competitors and prevents cytochrome P450 from metabolizing other compounds.
The extent to which cannabidiol behaves as a competitive inhibitor of cytochrome P450 depends on how tightly CBD binds to the active site of the metabolic enzyme before and after oxidation. This can change greatly, depending on how—and how much—CBD is administered, the unique attributes of the individual taking this medication, and whether isolated CBD or a whole plant remedy is used.
If the dosage of cannabidiol is low enough, it will have no noticeable effect on CYP activity, but CBD may still exert other effects. There is no clearly established cut-off dose, below which CBD does not interact with other drugs. A 2013 report on a clinical trial using GW Pharmaceutical’s Sativex, a whole plant CBD-rich sublingual spray, found no interactions with CYP enzymes when approximately 40mg of CBD were administered. A subsequent clinical trial, however, found that 25mg of orally administered CBD significantly blocked the metabolism of an anti-epileptic drug.
Any pharmaceutical, nutraceutical or green rush scheme to exploit the therapeutic potential of CBD must reckon with the fact that cannabidiol can both inactivate and enhance various cytochrome P450 enzymes in the liver—and this can potentially impact a wide range of medications. Drug interactions are especially important to consider when using life-saving or sense-saving drugs, drugs with narrow therapeutic windows, or medications with major adverse side effects. In particular, those who utilize high doses of CBD concentrates and isolates should keep this in mind when mixing remedies.