CBD and the Grapefruit Rule

CBD and the Grapefruit Rule
CBD and the grapefruit rule | CBD4Beginners - all about the UK CBD market

Have you ever heard how people should follow the ‘grapefruit rule’ when taking CBD? What does that even mean? The rule refers to CBD’s interaction with a liver enzyme in a similar way to grapefruit. If a medication asks you to avoid grapefruit while taking it, chances are you shouldn’t be taking CBD with it either.

CBD and grapefruit

CBD is a popular component produced from industrial hemp. Many people take it because they believe it may help them with depression, chronic pain, anxiety, inflammation, and more. CBD has gained prominence because of its perceived therapeutic benefits without the psychoactive effects associated with THC. It is non-addictive and non-psychotropic and generally well-tolerated by the human body. So, where does the grapefruit rule come in?

When taking CBD orally, for example when you take CBD gummies, pills, capsules, oils, or tinctures, you are ingesting CBD. This is carried to the liver and metabolized there before it enters the bloodstream. An aspect that some CBD consumers sometimes ignore is that it interacts with certain medications, akin to the well-known “grapefruit rule.”

This rule, typically associated with grapefruit, also applies to CBD due to its effect on the cytochrome P450 enzyme system in the liver. In a nutshell, if your GP has asked you to avoid grapefruit because of the medication you’re on, you may need to avoid CBD as well because they both get metabolized by the same liver enzyme.

Let’s take a look at how CBD is carried into the liver and metabolized and what that means for people on medication.

The cytochrome P450 enzyme

The cytochrome P450 enzyme is central to medication metabolism. It affects how substances are broken down and processed in the body. Many common medications are broken down and processed by this enzyme before they reach the bloodstream, including statins and antidepressants. In fact, a whopping 50% of all drugs are metabolized by the cytochrome P450 enzyme.

So, what’s the problem with grapefruit? Grapefruit is known to inhibit these enzymes. Grapefruit contains some chemicals called furanocoumarins. These inhibit the breakdown and processing of some drugs. As a result, the body experiences higher concentrations of these drugs in the bloodstream, which can dangerously boost both their efficacy and toxicity and increase the chances of side effects.

Pharmacological companies have carefully studied and researched the dosage for their medications. They have taken into account how long it takes for the liver to metabolize them and how much ends up in the bloodstream in the end (aka their bioavailability). When grapefruit comes in and skews the time it takes for the body to metabolize the medication, the drug stays in the intestines for much longer than it’s supposed to. This can cause toxicity.

Does CBD act the same way as grapefruit?

Oral CBD ends up in the liver, where it acts in the same way as grapefruit. When it interacts and engages the cytochrome P450 system, it can affect the metabolism of various medications. 

CBD often engages the cytochrome P450 before any other medication has an opportunity to do so. It acts as a competitive inhibitor, which means that the liver needs to process CBD first before moving on to other compounds. As a result, medication can linger in the intestine and other parts of the body for longer than drug companies estimated when determining the right dosage.

CBD and grapefruit affect both enzymes and transporters

Interestingly, some medications are either metabolized by enzymes or transporters. When the enzyme is blocked because it has been hijacked by CBD, too much medication lingers in the body before it accesses the liver. In the case of blocked transporters, grapefruit — and CBD — can block their effectiveness and too little medication ultimately reaches the bloodstream.

Not everyone will be affected, though, as some people have higher levels of CYP450 than others. When they take CBD, there is still plenty of CYP450 left to metabolize their medication. 

CBD, CYP450, and competing medication

Just like grapefruit, CBD can affect how quickly and in what way the liver metabolizes certain medications before they enter the bloodstream. When CBD inhibits these enzymes, it can increase the levels of drugs such as anticoagulants, antihistamines, and certain antiepileptic medications, among others. This interaction can cause unexpected side effects or even toxicity. 

Many medications are affected by this interaction, including some blood thinners, some anti-histamines, some corticosteroids, some anti-anxiety drugs, some high blood pressure drugs as well as some cholesterol drugs.

For example, patients on blood thinners like warfarin might experience elevated levels of the medication and an increased risk of bleeding complications. Antidepressants are also affected by the grapefruit and CBD rule. Too much or too little of the medication might enter the bloodstream and cause ups and downs in mental health.

Tips on the grapefruit rule

You can take a few practical steps to maximize the benefits of CBD in your wellness routine without impacting how other medications you are taking are working in your body.

Here are some user-friendly guidelines:

Consult with your GP

The interaction between CBD and the cytochrome P450 system doesn’t mean you should avoid CBD altogether, but it does mean you should be mindful and consult with your GP.  Talk to them before integrating CBD into your health routine, especially if you are already taking some prescribed medications and even some over-the-counter medications.

Your GP will be able to monitor drug levels and adjust dosages as necessary to mitigate any adverse effects. Also, if you are aware of this interaction, you can understand the potential risks and benefits of CBD and make more informed use of this compound. 

It’s all about striking a balance — enjoying the benefits of CBD while making sure it doesn’t adversely affect your health. Many people successfully include CBD into their lives with positive results and find their overall well-being improved. As always, being cautious and well-prepared is the best way to move forward.

Start with a low dose

If you and your GP decide that CBD is safe for you to use, start with a low dose. A low dose will require fewer resources from your liver and won’t engage the CYP450 enzyme as massively as one large dose.

Gradually increase it as needed while monitoring for any unusual effects or side effects. Keep track of your other health issues; if the CYP450 isn’t metabolizing your other medication properly, you will witness the effects on your body.

Monitor for side effects

Be aware of any changes in how you feel after starting CBD, especially if you notice increased side effects from your medications. Symptoms to watch for can include dizziness or excessive drowsiness. If you notice any sign of significant side effects, consult with your GP.

Regular blood tests

If you’re on medications that require blood level monitoring (such as blood thinners or certain anti-seizure drugs), regular blood tests can confirm that drug levels remain within a safe range. Your GP can adjust dosages if necessary.

Space out timing

Sometimes, taking CBD at a different time than your other medications can help minimize potential interactions. It usually takes four hours for any substance to be metabolized by the liver. If you can space out your existing medication away from CBD, then you give time to your liver to build the CYP450 enzyme so that it can safely metabolize CBD without affecting the breakdown of your other medication. Ask your GP if this might be an option for you.

Micro-dose CBD

Some people choose to micro-dose CBD. Instead of taking one large dose per day, they divide it into smaller ones which they take more frequently throughout the day. Smaller CBD doses will activate lower levels of the CYP450 enzymes while still leaving enough for other medications to be metabolized.

Learn about CBD

The best way to protect yourself, besides talking to a GP, is to stay informed about which medications you are taking and how they interact with the cytochrome P450 enzyme system. Common ones include blood thinners, heart medications, and certain anti-anxiety drugs. There are online resources and databases where you can check potential interactions.

Choose high-quality CBD products

As with most things in life, choose high-quality, third-party-tested CBD products to ensure that you’re getting a pure and consistent dose. Products that are accurately labelled can help you manage your intake more effectively. The CBD market is less regulated than the medicinal one, so it’s up to you to check which CBD brand you choose. Choose wisely!

CBD and the grapefruit rule

CBD and grapefruit act in a similar way in the body: they reach the liver quickly and engage the CYP450 system before other medications. That leaves little room for other medications to be properly metabolized and carried to the bloodstream.

This doesn’t mean that you should forego CBD altogether. Reach out to your GP and discuss how you feel that CBD could help you with your well-being routine. Space your existing medication away from your CBD consumption and opt for a low dose. 

Whenever possible, choose organic CBD products. Check with the manufacturer to confirm that they test their products and check the Certificate of Analysis, often found online, for the CBD content, the existence of harmful chemicals or heavy metals, and the content of other cannabinoids. To get the purest, safest CBD products, check our reviews for the best UK CBD oil brands and the best UK CBD stores!

Nicholas C. Rossis

Nicholas Rossis, PhD is a specialized, NSF-trained writer who has written hundreds of posts on CBD and nutritional supplements. His work combines critical acclaim with the analysis of the latest news, studies, research, and legal developments in the world of CBD, providing readers with valuable data and insights.

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