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What Drugs Should not be Taken with CBD? Ask a Pharmacist

Posted by Dr. Leslie Mudd, PharmD on Oct 15th 2020

What Drugs Should not be Taken with CBD? Ask a Pharmacist

CBD is generally safe to take with other medications, but you might be surprised to find out which ones.

Many people interested in CBD are concerned how CBD might interact with their existing medications. Initial research has concluded that CBD may interact with certain medications. Please keep in mind that this is not medical advice. For more specific information on CBD and drug interactions for you personally, please consult your doctor.

We wrote this post as a guide to help you better understand possible drug interactions with CBD when you talk with your doctor. Cornbread Hemp does not market its CBD products as a medicine or a drug, and nothing in this post should be considered such.

The Food and Drug Administration has not issued regulations on CBD and still has concerns about the CBD industry. Even though CBD is not considered to be a drug, you should use it with the same thoughtfulness that you would use a medicine. Take CBD with the safety precautions that you take your prescription meds.  

The CBD-Grapefruit Comparison

There is still much to learn about how cannabinoids like CBD interact with the human body. The FDA still has concerns, and consumers need to do their own research to draw their own conclusions.

Some experts, including those at Harvard Medical School, have made this interesting observation: if a medication has a “ Grapefruit Juice Warning,” then CBD will likely have a similar interaction.1 CBD acts similarly to grapefruit juice in the liver,2 so if you take a medicine that does not mix well with grapefruit juice, then your medicine might not mix well with CBD, either. Like CBD, grapefruit juice is not a drug, but could affect how medications perform in the body.3

The medical community has known for years about grapefruit juice interactions, but this may not be well known by the general public. CBD and drug interactions like the one grapefruit juice4 has are even less well known by the medical community, so it's important to talk with your doctor first to avoid any negative side effects.

In 2018, Dr. Peter Grinspoon wrote on the Harvard Health Blog: “CBD can increase the level in your blood of the blood thinner coumadin, and it can raise levels of certain other medications in your blood by the exact same mechanism that grapefruit juice does.”5 The brand name for coumadin is Warfarin.

This similarity stems from the fact that both grapefruit juice and CBD affect the P450 liver enzyme.6 The cytochrome P450 system is much more complicated than this brief discussion will allow. It metabolizes 70 to 80 percent of all drugs that enter the body.7 

Certain compounds found in grapefruit juice are bioactive. Bioactive means that these are plant chemicals that have activity in human biology. These compounds can inhibit the activity of liver isozymes. With these isozymes inhibited, they cannot metabolize another substance. That results in higher blood levels of the other drug. If you are on liver-metabolized medications, you might want to bypass CBD capsules and grapefruits. Note—this does not apply to oranges, just grapefruits and a few other types of citrus fruits.

A CBD Study in Humans

In 2017, the International League Against Epilepsy published a study in humans on the interactions between cannabidiol and 19 commonly used anti-epileptic drugs. The study looked at 39 adults and 42 children.

In the study, only two of the 19 epilepsy medications exceeded the therapeutic range when paired with CBD. This emphasizes the importance of monitoring anti-epileptic drugs levels and liver function tests during treatment with high servings of CBD.8

Accurate Dosing is Key

There is a prescription drug approved by the FDA made from CBD isolate.9 But the interactions for that drug are most likely not the same as those with full spectrum CBD supplements intended for wellness. Here’s why: the recommended CBD dosage or serving size is significantly different.

The makers of the prescription drug recommend a dose of 10 mg/kg, twice a day.10 A 200-pound man is about 90 kg. That would make his serving 900 mg twice a day. This is a large serving of CBD.  

In the 2017 human study, the CBD doses started at 5 mg/kg/day. The study’s dosage increased every 2 weeks by 5 mg/kg/day up to a maximum of 50 mg/kg/day — a very large amount of CBD.11

Most folks interested in full spectrum CBD for wellness take considerably less CBD—perhaps a serving size of 25 or 50 mg, one to three times a day.

Final Thoughts on Taking CBD Oil With Other Medications

At larger pharmaceutical doses of CBD, there might be the possibility of drug interactions between CBD and medicines. At lower serving sizes, the risk of drug interactions is small, but not zero.

When you take CBD, make sure you choose a trustworthy brand. Are there lab tests available that you can easily read and understand the CBD content? Is it USDA certified organic? To reduce variability, take your CBD oil at the same serving size and same time every day. Pay attention to any medicines that you use—even herbals and vitamins.  

If any of your other medications or supplements have a caution about not using with grapefruit juice, then you may not want to take CBD with them either. Please talk to your doctor for further information.

This post has not been intended as medical advice. CBD is not a drug. The FDA did not evaluate these statements. Cornbread Hemp products are not intended to diagnose, treat, cure, or prevent any disease.

References

1.

Grapefruit Juice and Some Drugs Don’t Mix | FDA. https://www.fda.gov/consumers/consumer-updates/grapefruit-juice-and-some-drugs-dont-mix. Accessed August 12, 2020. The whole section

2.

CBD-Drug Interactions: Role of Cytochrome P450. https://www.projectcbd.org/medicine/cbd-drug-interactions/p450. Accessed August 12, 2020. Under ‘grapefruit and ganja’ heading, 3rd paragraph, 2nd and 3rd sentence

3.

CBD-Drug Interactions: Role of Cytochrome P450. https://www.projectcbd.org/medicine/cbd-drug-interactions/p450. Accessed August 12, 2020. Under ‘grapefruit and ganja’ heading, 3rd paragraph, 2nd

4.

CBD-Drug Interactions: Role of Cytochrome P450. https://www.projectcbd.org/medicine/cbd-drug-interactions/p450. Accessed August 12, 2020. Under ‘grapefruit and ganja’ heading, 3rd paragraph, 2nd and 3rd sentence

5.

Cannabidiol (CBD) — what we know and what we don’t - Harvard . https://www.health.harvard.edu/blog/cannabidiol-cbd-what-we-know-and-what-we-dont-2018082414476. Accessed August 12, 2020. Under ‘is cannabidiol safe?’ section, 1st paragraph, 2nd sentence

6.

CBD-Drug Interactions: Role of Cytochrome P450. https://www.projectcbd.org/medicine/cbd-drug-interactions/p450. Accessed August 12, 2020. Under ‘grapefruit and ganja’ heading, 3rd paragraph, 2nd and 3rd sentence

7.

Cytochrome p450 - Genetics Home Reference - NIH. https://ghr.nlm.nih.gov/primer/genefamily/cytochromep450. Accessed August 12, 2020. Under ‘Cytochrome p450’ heading, 3rd paragraph, last sentence

8.

Gaston, Tyler E et al. “Interactions between cannabidiol and commonly used antiepileptic drugs.” Epilepsia vol. 58,9 (2017): 1586-1592. doi:10.1111/epi.13852. The whole study

9.

FDA Approves First Drug Comprised of an Active Ingredient Derived . https://www.fda.gov/news-events/press-announcements/fda-approves-first-drug-comprised-active-ingredient-derived-marijuana-treat-rare-severe-forms. Accessed August 12, 2020. Refer to the title.

10.

EPIDIOLEX (cannabidiol) oral solution. https://www.accessdata.fda.gov/drugsatfda_docs/label/2018/210365lbl.pdf. Accessed August 12, 2020. Under ‘dosage and administration’ section, 4th bullet point

11.

Gaston, Tyler E et al. “Interactions between cannabidiol and commonly used antiepileptic drugs.” Epilepsia vol. 58,9 (2017): 1586-1592. doi:10.1111/epi.13852. The whole study. Under ‘methods’ section, 3rd paragraph, 4-7th sentence