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CBD and Drug Interactions


By now you’ve probably heard about all of 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 negative interaction with other drugs.

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.


Have you ever noticed that it can take up to an hour to feel the effect of a medication you took?

This is because the drug needs to be processed by your liver.

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

According to the American Academy of Family Physicians, these liver enzymes are responsible for breaking down about 90% of the drugs we’re taking[i].

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 anesthetics. That’s a lot of commonly used drugs.

So if you’re taking CBD or 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. This is why we advise you to always speak with your doctor before taking CBD.


Just like many other drugs, CBD is broken down by the cytochrome P450 enzymes.

CBD also has a special effect on the P450 enzymes: when CBD attaches to the enzymes, it inhibits them[iii] and prevents them from breaking down other drugs.

This effect can be both advantageous and problematic for the CBD user.


CBD’s action on the P450 enzymes causes other medications you may be taking to stay in your blood for longer than normal.


CBD inhibits the P450 enzymes and stops them from doing their normal job of breaking down your other medications. Since these medications are not getting broken down, they stick around and hang out in your system. Basically, CBD can make other drugs overstay their welcome in your body.

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, block the blood vessels, and cause a stroke or heart attack.

We researched a study where a patient[iv] was hospitalized and diagnosed with gastrointestinal bleeding. After about a week in the hospital, he was sent home only to return a couple of weeks later for persistent bleeding of the nose and easy bruising. Of course, his doctors had to investigate if the patient was doing anything to contribute to these problems.

They discovered that the patient had been smoking cannabis.

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!

Consider another example: a group of children who were taking antiepileptic drugs like clobazam and norclobazam were also given CBD[v]. 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!

But why is this a negative effect if the seizures were reduced?

Because the more the antiepileptic drugs stay in the system, the more side effects they will produce like restless sleep, lethargy, tremors, appetite loss, urinary problems, loss of motor control, and irritability.

Long-term users of antiepileptic drugs are at a higher risk for developing liver disease, and if their levels always stay up, then it could lead to irreversible liver damage!

The same goes for strong painkillers like codeine and oxycodone[vi]. 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 good thing, it can also be a problem because it leads to a higher concentration of the medication in the blood. A higher concentration of the medication will increase the chances of adverse side effects from a drug as well as potentially be harmful to your liver.

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

The Advantages of Using CBD with Other Drugs

CBD can enhance another drug’s effects so well that the user can 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 dose of their epilepsy medication. This is a big deal. By taking a smaller dose of the epilepsy meds, the patient is liberated from the adverse side effects they were experiencing from the higher dose they were using before they added in the CBD.

Under the supervision of a doctor, adding CBD to your daily regimen has the potential of being an excellent add-on therapy for many medical conditions.

CBD-rich products could potentially be considered as an add-on therapy for patients going through chemotherapy. CBD and THC (especially when used together) are both very good at relieving nausea, vomiting, and the loss of appetite experienced from chemotherapy[vii]. CBD has anticancer effects of its own and enhances the effects of chemotherapy drugs since it also prompts cancer cell death[viii].

Like 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, CBD doesn’t harm healthy cells (chemo can harm good and bad cells at the same time). Instead, CBD, as a potent antioxidant, protects non-cancerous, healthy cells while killing off cancerous cells.


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[ix], upset stomach, diarrhea, and sedation.

📷If you do get some mild but unpleasant side effects with CBD, try decreasing the dose.

Oftentimes, negative side effects from CBD are from taking too high of a dose. Start with a low CBD dosage first, assess its effects, and either increase or decrease the dose until you find a dose that can effectively control your symptoms.

If you’re just starting out and you don’t know how much CBD to take, a typical start off point is 5 – 10 mg, one or two times per day.

But before you add CBD to your treatment regimen, consult with your doctor first. He’s familiar with your medical condition and the medications you’re taking. He can order blood tests to monitor the levels of your medications in your blood and adjust their dosages to avoid complications.

Do the “grapefruit test” with your doctor. Thanks to Martin Lee of Project CBD for inspiring the creation of the “grapefruit test”. The “grapefruit test” is when you ask your doctor if any of the medications you are taking are affected by eating grapefruits. The way our body metabolizes grapefruits can affect many commonly used drugs. CBD acts in the same way as a grapefruit, only even stronger.

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

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, we want you to be cautious.

Work with your doctor or a pharmacist you trust. Be compliant with their 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 tell him you want to take CBD. Alternatively, he may just recommend you don’t take your CBD too closely to the time of day you take your other medication.

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


[i] Tony Lynch and Amy Price. August 1, 2007.

American Academy of Family Physicians, The Effect of Cytochrome P450 Metabolism on Drug Response, Interactions, and Adverse Effects.

[ii] Indiana University, Department of Medicine, P450 Drug Interaction Table.

[iii] S Yamaori, et al. February 26, 2011.

The National Center for Biotechnology Information, Potent inhibition of human cytochrome P450 3A isoforms by cannabidiol: role of phenolic hydroxyl groups in the resorcinol moiety.

[iv] Weeranuj Yamreudeewong, et al. June 16, 2009.

Annals of Pharmacotherapy, Probable Interaction Between Warfarin and Marijuana Smoking.

[v] AL Geffrey. June 26, 2015.

The National Center for Biotechnology Information, Drug-drug interaction between clobazam and cannabidiol in children with refractory epilepsy.

[vi] Adriane Fugh-Berman, et al.

Department of Health, Medical Cannabis: Adverse Effects & Drug Interactions.

[vii] Linda A. Parker, et al. August 2011.

The National Center for Biotechnology Information, Regulation of nausea and vomiting by cannabinoids.

[viii] DI Abrams, MD. March 23, 2016.

The National Center for Biotechnology Information, Integrating cannabis into clinical cancer care.

[ix] P Consroe, et al. November 1986.

The National Center for Biotechnology Information, Open label evaluation of cannabidiol in dystonic movement disorders.

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