Many substances, whether they be pharmaceutical prescriptions or even fruits like grapefruit, have the potential to interact with other medicines that you’re already taking. While CBD is largely safe on its own, it does also pose a risk of interacting with other medications. The aftereffects of such interactions can be risky, so it’s imperative to know how CBD can mingle with your medications.
Enzyme Induction vs. Enzyme Inhibition
Before we delve into the nitty-gritty of the drug interactions of CBD, let’s learn a few related terminologies — namely, enzyme induction and enzyme inhibition.
Virtually all medications and supplements (including CBD) taken via mouth are processed and broken down in your liver. Moreover, these pills can excite or inhibit your liver’s enzyme systems.
A substance that “induces” the liver enzyme systems accelerates the rate at which another compound is metabolized (broken down). This lowers the levels of that pill or compound in your system, dulling its therapeutic benefits and other effects.
Likewise, a compound that reaches your liver to “inhibit” the activity of the enzymes therein will slow down the breakdown of the targeted substance (pill). The levels of that targeted substance will eventually rise — sometimes to toxic levels — adding to its effects (both unpleasant and favorable).
CBD Can Worsen Medicine’s Side Effects
If you’ve ever been told by your physician not to eat grapefruit with a certain medicine, chances are that taking CBD with that same medicine might not be ideal too.
Wondering why that’s so?
Both these products have a potential to inhibit a certain set of liver enzyme systems called cytochrome P450. These liver enzymes are a major family of proteins involved in processing and breaking down other medications. CBD is unique in that it can act on the cytochrome P450 (CYP) enzymes while these enzymes act on and process CBD too. That is, CBD is metabolized by the CYP enzymes as well as it strongly deactivates them.
By displacing other chemicals (medicines) from binding to the cytochrome P450, CBD inhibits the enzymes from metabolizing other compounds. In fact, CBD is the strongest deactivator of the liver enzymes amongst all the cannabinoids. This means that you need to be extremely cautious about what’s going in your system along with CBD.
The CYP liver enzymes metabolize about a quarter of all the pills, including but not limited to:
- Warfarin (a blood thinner, the combination can cause serious bleeding)
- Certain blood pressure-lowering medications
- Benzodiazepines used to address anxiety in the short-term (combination can cause excessive sedation)
- Medications used to treat seizures (a 2017 study conducted at the University of Alabama showed sizeable interaction between CBD and certain antiepileptics. The authors emphasized the importance of monitoring the levels of these drugs as well as the liver function tests during treatment with CBD).
- Antidepressants
- Antipsychotics
- Viagra
When inhibited, the enzymes can no longer carry out their function. Using CBD with these medications may thus amp up their blood levels, putting you at risk of serious side effects.
So, be sure to tell your doctor when planning to take CBD while being on some pharmaceutical or herbal product. If need be, your healthcare provider may need to work with the dose of that pill to avoid any unexpected, toxic side effects.
CBD Can Make Other Meds Less Effective
While CBD blocks the liver enzymes in the short term, it tends to induce them with repeated use. These enzymes, in turn, speed up the breakdown of the meds metabolized by them, making them less effective. If this is the case, your doctor might need to increase the dose of the meds that interact with CBD in this way, allowing them to work effectively.
Medicines Can Add to CBD’s Effects
A few antibiotics and meds used to treat fungal infections also put the brakes on the liver enzymes involved in processing CBD. The reduced metabolic rate slows down the breakdown of CBD, the levels of which then double in your system. Eventually, the effects of CBD are enhanced.
Certain Medications Can Make CBD Less Effective
If you really want to reap the full benefits of the cannabinoid, be sure to talk to your doctor if any of your meds will interact with CBD. Just like a few medicines can enhance CBD’s effects, some can also interfere with its desired health benefits. These medicines are the ones that induce liver enzymes and speed up CBD’s metabolism. So, more CBD is broken down with a little amount reaching your circulation. And you won’t be able to achieve the desired health benefit from CBD.
Medications used to treat seizures (antiepileptics) top this list. Other common ones in this category include:
- Rifampin (an antibiotic)
- John’s Wort (an herbal antidepressant)
- Antiviral meds, especially those designed for HIV
Does CBD Interact With Other Meds at Lower Serving Sizes?
There’s no clear cut-off dose below which CBD doesn’t interact with other meds. In a 2013 report, a 40 mg dose of Sativex (a whole plant CBD-rich extract) didn’t show any interactions with CYP enzymes. However, in a clinical trial carried out later, a 25mg serving of CBD curbed the metabolism of an anti-epileptic.
CBD and Anti-Cancer Meds
Many consumers have been turning to medical cannabis and CBD to relieve the side effects of anti-cancer treatments. However, many people aren’t aware that CBD — just like grapefruit — can inhibit the metabolism of chemotherapy drugs too. And why not? After all, many of these chemotherapy agents require CYP enzymes for their inactivation. This implies that using CBD along with these agents (without adjusting their dose) can cause their levels to skyrocket, giving rise to potentially dangerous side effects.
Caution Never Hurts
CBD is generally a safe and effective product. However, because its effects aren’t yet well-known and more studies need to be done, it’s better to be cautious when using CBD with medications. Doing a little research and checking with your doctor will help you make an educated, safe decision about incorporating CBD into your life.
To your knowledge does CBD have any negative side effects with cholesterol medicines??
Hi George! That's something that would be best to speak with a doctor about.