CBD and drug interactions
Research to date shows that CBD is generally safe and has few, if any, minor side effects. But there’s one big caveat: CBD does have the potential to interact with some medications. The concern has to do with how the body metabolises certain substances.
Drug metabolism and CYP450 enzymes
When you take a medication or other substance, your body has to metabolise it, or break it down. Drug metabolism happens throughout the body, such as in the gut, but the liver does a big part of the job, too.
A family of enzymes called cytochrome P450 (CYP450) does the important work of converting foreign substances so they can easily be eliminated from the body.
But some medications or substances affect CYP450, either by slowing or speeding up drug metabolism. That change in metabolism rate can alter how your body processes the medications or supplements you take — hence a drug interaction.
Why does CYP450 matter when it comes to CBD and medications?
The CYP450 family of enzymes is responsible for metabolising several cannabinoids, including CBD, research shows. Specifically, CYP3A4, an important enzyme within the CYP450 family, does the task. But during this process, CBD also interferes with CYP3A4.
The CYP3A4 enzyme is in charge of metabolising about 60 percent of clinically prescribed medications. But if CBD is inhibiting CYP3A4, it can’t work as effectively to break down the medications in your system.
The reverse can happen, too. Many medications inhibit CYP3A4. If you then take CBD while on these medications, your body can’t work to process the CBD as effectively.
If your body is breaking down your medication too quickly, it’s going to leave your system sooner than it should. This might mean that you’re not getting the full effects of the medication, for as long as you need them. Imagine you’re taking an antibiotic. Even though you’ve taken the correct amount, you might not have enough in your system to fight off the infection. On the other hand, if your body isn’t breaking down the drug quickly enough, you might still have high levels in your system by the time you take your next dose. That could intensify any side effects and potentially put you at risk of harm.
Types of medications that might interfere with CBD
Warfarin, a popular blood thinner, had the potential to cause significant medication interactions with CBD.
Amiodarone, a cardiac rhythm medicine.
Levothyroxine, a thyroid medicine.
Clobazam, lamotrigine, and valproate, among other seizure drugs.
Look for the grapefruit warning
Although studies are still ongoing to determine potential interactions between CBD and specific medications, there’s one rule of thumb that can help consumers in the meantime: Avoid CBD if your medications have a grapefruit warning on the label.
This warning indicates that people taking the medication should avoid consuming grapefruit or grapefruit juice.
Consuming grapefruit while on one of these medications can lead to a higher concentration of the medication in the bloodstream and adverse side effects or even an overdose.
More than 85 drugs interact with grapefruit and some closely related citrus juices. Seville oranges (often used to make orange marmalade), pomelos, and tangelos (a cross between tangerines and grapefruit) might have the same effect as grapefruit juice. That’s because chemicals in grapefruit known as furanocoumarins inhibit CYP3A4, in a similar fashion as CBD. The result is a slowed metabolisation of medications.
According to the NHS, the following drugs are predicted to interact with grapefruit (and therefore possibly CBD)
Drugs used to treat cancer (crizotinib, dasatinib, erlotinib, everolimus, lapatinib, nilotinib, pazopanib, sunitinib, vandetanib, vemurafenib)
Drugs used to treat or prevent infections (erythromycin, halofantrine, maraviroc, primaquine, quinine, rilpivirine)
Drugs used to treat high cholesterol (atorvastatin, lovastatin, simvastatin)
Drugs used to treat heart and blood vessel conditions (amiodarone, apixaban, clopidogrel, dronedarone, eplerenone, felodipine, nifedipine, quinidine, rivaroxaban, ticagrelor)
Drugs affecting the central nervous system (oral alfentanil, buspirone, dextromethorphan, oral fentanyl, oral ketamine, lurasidone, oxycodone, pimozide, quetiapine, triazolam, ziprasidone)
Drugs used to treat nausea (domperidone)
Immunosuppressants (cyclosporine, everolimus, sirolimus, tacrolimus)
Drugs used to treat urinary tract conditions (darifenacin, fesoterodine, solifenacin, silodosin, tamsulosin)
When you understand how CBD affects drug metabolism, it’s easy to see how mixing it with certain drugs could cause some unwanted and potentially harmful effects. This is why we always recommend speaking to your doctor first.
Your doctor will be able to review your medications and check how they interact with CBD. That doesn’t necessarily mean that you can’t take CBD gummies or other CBD products. In many cases, it might just mean your dosage needs to be adjusted to make sure it’s accurate and safe.