CBD and Drug Interactions

CBD and Drug Interactions

It’s very important that you understand the effects CBD has on other medications so that you can decrease the chance of experiencing any problems.
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jen keehn

Written by Jen Keehn

Updated January 28, 2021

Dr. El-Hajj

Medically Reviewed by Dr. Sandra El-Hajj


With every passing year surfaces new health trends aiming at making people healthier. Among the numerous crazes out there comes CBD. I am sure you have heard repetitively about the benefits of adding CBD to your supplement regimen.

But did you know that CBD can interact with other drugs you are taking? 

CBD can have both a positive and a negative interaction with other drugs. So, to be safe, it’s very important to understand the possible effects that CBD has on other medications to minimize the chance of experiencing any problems.

If you want the summarized version of CBD-drug interactions, you can check our article CBD Drug Interactions: Easy Guide. This article provides a more in-depth look at such an effects. 

Drugs and Your Liver

Illustration Of Drugs And Human Liver

Have you ever noticed that it can take up to an hour to feel the effect of a medication you took? The reason behind such a wait is that the medication needs to go into your digestive system, get metabolized and absorbed by your gut and bloodstream to reach the liver too. 

Our liver is an organ that is located in the abdomen, on the upper hand size. It weighs around three pounds and has so many functions including cleansing the blood from potential toxins. When you two drugs that interact negatively together, you are creating a build up of medications that will disrupt the proper functions of the liver1.

The liver has special enzymes called the cytochrome P450, which have the function of breaking drugs down into smaller bits called metabolites. In their small form, our cells can absorb them better or eliminate them properly. 

So, the liver would break down any medication, supplement or herbal pills that we take orally. Under normal circumstances, the process is efficient does not cause any harm. Most medications are tested carefully before being approved for personal use2.

According to the American Academy of Family Physicians, these liver enzymes are responsible for breaking down about 90% of the drugs we’re taking. Some of these drugs[ii] include NSAIDs, beta blockers, angiotensin II blockers, antiarrhythmics, calcium channel blockers, anti-cholesterol drugs, proton pump inhibitors, antibiotics, HIV antivirals, anti-epileptics, anti-diabetics, antipsychotics, antidepressants, anti-anxiety medications, antihistamines, and anesthetics3These are commonly used drugs.

So, knowing the CBD interaction with the liver P450 and if you are planning to include CBD in your medication regimen, there's a high chance that CBD is going to affect other drugs you’re currently taking. Such an interaction may lead to harmful side effects. So, we advise you to always speak with your doctor before taking CBD.

CBD and the Cytochrome P450 Enzymes

Just like many other drugs, CBD is broken down by the cytochrome P450 enzymes. This cannabis constituent also has a special effect on these enzymes: when it attaches to the them, it inhibits the enzyme preventing the break down of other drugs. This effect can be both advantageous and problematic for the CBD user. 

The Disadvantages of Using CBD with Other Drugs

CBD's action on the P450 enzymes causes other medications you may be taking to stay in your blood for longer than normal. They bioaccumulate at large doses.

Here's how it works

CBD inhibits the P450 enzymes and prevents them from doing their normal job: breaking down any medications you may be taking.

When these do not get broken down, they accumulate in your system, too large to be absorbed. So, one of the negative effects of CBD when you are on other pills is to let your body accumulate large amounts of unprocessed and unwelcomed pills.

This can be problematic for the CBD user. Take for example an anticoagulant drug called warfarin. This drug makes the blood thinner so blood clots won’t form and block the blood vessels causing a stroke or heart attack4.

A patient was hospitalized and diagnosed with gastrointestinal bleeding. He remained about a week in the hospital, then was sent home. A couple of weeks later, he was admitted with persistent bleeding of the nose and easy bruising. Doctors investigated to figure out what was happening in his system. What they discovered was that the patient was smoking cannabis to manage his depression. After nine months of stopping smoking, the patient did not encounter any bleeding while on his warfarin medications5.

Man Lights A Joint

So what does this show? 

While we don't know the exact cannabinoid profile of the cannabis the patient was using, the cannabis may have increased the anticoagulant effect of warfarin in thinning his blood, which thus led to his bleeding problems! Marijuana inhibited the metabolism of the blood thinner by displacing it from regular protein-binding sites.

Consider another example: a group of children who were taking antiepileptic drugs like clobazam and norclobazam were also given CBD. While CBD significantly helped reduce the number of seizures they were having, blood tests also revealed a higher concentration of the antiepileptic drugs in the children’s blood! The reason why the seizures were more recurrent was simple. The antiepileptic drugs were accumulating in the system, due to the presence of CBD, which led to side effects such as restless sleep, lethargy, tremors, appetite loss, urinary problems, loss of motor control, and irritability.

Such a drug interaction was found risky since long-term users of antiepileptic drugs are at a higher risk for developing liver disease. So, elevated levels could lead to irreversible liver damage6.

The same effects were observed with strong painkillers like codeine and oxycodone. While CBD helps them stay longer in the system and prolong their pain-killing effects, it also increases the risk of developing adverse side effects from these drugs like constipation, drowsiness, vomiting, nausea, and even liver disease.

CBD can increase the efficacy of many commonly used medications. While this can obviously be a positive effect, it can also be a problem leading to a higher concentration of the medication in the blood. This may increase the chances of adverse side effects from a drug and harm the liver.

But not all interactions between CBD and other drugs are negative. CBD can beneficially interact with certain drug as well.

The Advantages of Using CBD with Other Drugs

CBD And Other Drugs

CBD may enhance another drug’s effects to the point that the user will be able to decrease the dosage of the other drug. One example of this is with epilepsy medication.  

For some people, combining CBD with their daily epilepsy medication allows them to decrease the daily dose of their medicine. This can be a breakthrough as a smaller dose of any medication can make the patient feel liberated from possible adverse side effects they were experiencing from high doses of medication.

Go here to read Alex's story about how he uses CBD to decrease his epilepsy medication dose

Under the supervision of a doctor, adding CBD to your daily regimen may have the potential of being an excellent add-on therapy for many medical conditions. This can be the case for those going through chemotherapy. CBD and THC (especially when used together) are both effective in relieving nausea, vomiting, and the loss of appetite experienced by cancer patients undergoing treatment. 

CBD has anticancer effects of its own and enhances the effects of chemotherapy drugs since it also prompts cancer cell death7Like chemotherapy, CBD has demonstrated the ability to kill different types of cancer cells including breast, colon, leukemia, lung, prostate, and brain cancer cells. But unlike chemotherapy, it does not harm healthy cells.

Instead, CBD, as a potent antioxidant, protects non-cancerous, healthy cells while killing off cancerous cells.

Using CBD with Other Medications

CBD Oil And Different Medications

In numerous studies, CBD has been demonstrated to be a safe and effective drug. It has the potential to improve numerous medical conditions from acne to epilepsy and chronic pain, with very few side effects, if any at all.

While side effects are not common, they can happen. Some side effects you may experience with CBD are lightheadedness, dry mouth, upset stomach, diarrhea, and sedation. If you do get some mild but unpleasant side effects with CBD, try decreasing the dose8

Often, negative side effects from CBD result from taking high doses.

So, it is always advisable to start with a low CBD dosage first, assess its effects, and then either increase or decrease the amount until you find the right dose that can effectively control your symptoms.

If you are a new CND user and are not familiar with it, a typical start off point is 5 – 10 mg, one or two times per day. But, before adding CBD to your treatment regimen, it is always recommended to consult with your doctor first. 

You doctor knows your body by now and is familiar with any other medication you are taking. He can order blood tests to monitor the levels of these in your blood and adjust their dosages to avoid complications, if you decide to start with CBD products.

Also, those who decide on incorporating CBD into their lifestyle need to mention the “grapefruit test” to their doctor. This test was created by Martin Lee, from Project CBD. This test consists of analyzing with your doctor if you have any medication you are taking interact with the grapefruit.

Yes! Grapefruit can interact with some medications producing unwanted results. The way our body metabolizes grapefruits can affect many commonly used drugs. CBD acts in the same way as a grapefruit, only even stronger9.

If your doctor says yes to the grapefruit test, you know you need to discuss your CBD usage with them as well. If your doctor knows nothing about CBD, educate them about it. Show them our site.

While the interaction of CBD with other drugs is a real concern, we haven't come across many cases of serious complications experienced by people using CBD. Still, it is always essential to be careful!

Work with your doctor to craft any additional medication you want to include. Be compliant with his recommendations, especially when it comes to regular laboratory checkups, and report any side effects you may develop.

Your doctor may decide to monitor your blood work more closely, if you decide on CBD. They might just recommend you space out the medications and CBD products throughout the day.

When used safely, CBD may help you reduce your prescription medication dosages and ultimately their side effects as well.


1Damkier, P., Lassen, D., Christensen, M., Madsen, K. G., Hellfritzsch, M., & Pottegård, A. (2019). Interaction between warfarin and cannabis. Basic & clinical pharmacology & toxicology124(1), 28–31. https://doi.org/10.1111/bcpt.13152 


2Medications and the Liver. (n.d.). Retrieved January 28, 2021, from https://gi.org/topics/medications-and-the-liver/

3Lynch, T., & Price, A. (2007, August 01). The Effect of Cytochrome P450 Metabolism on Drug Response, Interactions, and Adverse Effects. Retrieved January 28, 2021, from https://www.aafp.org/afp/2007/0801/p391.html#:~:text=Cytochrome%20P450%20enzymes%20can%20be%20inhibited%20or%20induced,and%20statins%20often%20involve%20the%20cytochrome%20P450%20enzymes.

4Sinha, S., MD (Ed.). (n.d.). Warfarin Uses, Dosage, Side Effects. Retrieved January 28, 2021, from https://www.drugs.com/warfarin.html

5Yamreudeewong, W., Wong, H. K., Brausch, L. M., & Pulley, K. R. (2009). Probable interaction between warfarin and marijuana smoking. The Annals of pharmacotherapy43(7), 1347–1353. https://doi.org/10.1345/aph.1M064
6Geffrey, A. L., Pollack, S. F., Bruno, P. L., & Thiele, E. A. (2015). Drug-drug interaction between clobazam and cannabidiol in children with refractory epilepsy. Epilepsia56(8), 1246–1251. https://doi.org/10.1111/epi.13060

7Cannabis and Cannabinoids (PDQ®)–Health Professional Version. (n.d.). Retrieved January 28, 2021, from https://www.cancer.gov/about-cancer/treatment/cam/hp/cannabis-pdq

8Cannabidiol Side Effects: Common, Severe, Long Term. (n.d.). Retrieved January 28, 2021, from https://www.drugs.com/sfx/cannabidiol-side-effects.html

9Commissioner, O. (n.d.). Grapefruit Juice and Some Drugs Don't Mix. Retrieved January 28, 2021, from https://www.fda.gov/consumers/consumer-updates/grapefruit-juice-and-some-drugs-dont-mix

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