Looking at what drugs should not be taken with CBD can be a bit confusing. One simple trick that’s been discussed on the ever-so-resourceful online database suggests seeing if prescribed medications are safe to drink with grapefruit juice. Prescribed meds, (other than clobazam and valproic acid which is a big no-no) can be tested against grapefruit juice because grapefruit has some of the same features as CBD oil. It basically acts as a litmus test. 

Harmful Interactions: What Drugs Should Not Be Taken With CBD

The Grapefruit System

According to Harvard Medical School: “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 does”. 

Therefore if you are unable to drink grapefruit juice while taking your prescription medication, it may be unsafe to take CBD as well.

Why? 

• A lot of prescription drugs will include grapefruit warnings on the label, advising against eating citrus fruit while taking medication. 
• CBD acts on similar metabolites as grapefruit — therefore, drugs that carry grapefruit warnings may have similar risks with CBD intake. 
• Many medications are broken down in the liver and small intestine by a group of proteins called cytochrome P450 enzymes (CYPs). This process is what delivers a medication’s benefits to the intended target. 
• Grapefruit disrupts the activity of CYPs slowing these proteins from breaking down medication. 
• The fruit also increases the duration the drug stays in the system. 
• “Grapefruit Medication Interactions: Forbidden Fruit or Avoidable Consequences?” was a published study that showed that grapefruit can increase blood content levels when interacting with at least 85 different drugs. Consequences were severe with signs of irregular heartbeat, organ failure, internal bleeding, and death. 
• One 1993 study conducted by pharmacology researchers at the University of California, San Francisco, and published in the journal Biochemical Pharmacology, discovered that CBD, much like grapefruit, disrupts the normal function of cytochrome P450 enzymes in mice. The study postulated that while the blockage could allow patients to take lower doses of their prescriptions, it could also cause a toxic buildup of chemicals in the body. Since this study’s publication, several scientific and medical journals have published evidence of the grapefruit-like effects of CBD in humans.

CBD Drug Interactions With Common Over-The-Counter Medications

Now that you know how grapefruit can be used as a litmus test, that’s not the full story. Everything down to the type, quality and purity of CBD administered all affect how it interacts with your body and medication. 

The timing of CBD dosage and any other prescription drug also factors into how the two may interact in your body. 

Last but not least, every individual responds to medications differently, depending on genetics, age, weight, and other factors.

CBD with Ibuprofen: 

Ibuprofen is a nonsteroidal anti-inflammatory (NSAID) medicine that reduces pain and inflammation in the body. Ibuprofen has a risk of blood-thinning and can cause dizziness, shortness of breath, and nausea. 

Potentially, CBD can increase the duration and strength of ibuprofen, thereby increasing the risk of adverse side effects. 

CBD with Tylenol:

Acetaminophen, the generic name for Tylenol, is a common drug used for pain and fever relief. Acetaminophen carries a risk of liver damage and disease, with side effects including nausea, headaches, and insomnia.

Acetaminophen and CBD are both metabolized by CYP450, which decreases the effectiveness of both chemicals as they’re processed in the body. 

One controversial 2019 study, conducted by the University of Arkansas on mice and published in the journal Molecules, claimed that high doses of CBD contributed to liver toxicity, which could compound acetaminophen’s liver damage potential. However, the study’s authors have been accused of cherry-picking research and designing experiments to showcase potential CBD toxicity. The one study they cited with human test subjects did not show liver toxicity from CBD.

Further research is required to confirm potential interactions between CBD and acetaminophen but you still need to talk to your doctor for consumption.

CBD with Xanax:

Xanax breaks down in the liver using an enzyme called CYP3A4, which is inhibited by CBD. 

Taking CBD could potentially increase the amount of time Xanax is in the system increasing the likelihood of unwanted side effects. 

CBD may one day be considered an alternative to Xanax as various research, including a 2011 study published in the journal Neuropsychopharmacology, has documented the cannabinoid’s potential anti-anxiety properties.

No research has explicitly documented interactions between Xanax and CBD but you still need to talk to your doctor. 

CBD with Thyroid Medication: 

Thyroid medication is used to treat thyroid disorders, most commonly hypothyroidism (an underactive thyroid) via thyroid hormone replacement, and hyperthyroidism (an overactive thyroid) via anti-thyroid medication. Different medications achieve these objectives through different pathways in the body. Side effects of thyroid hormone replacement therapies include chest pain, anxiety, headaches, and vomiting. While rare, anti-thyroid medication side effects can include rash, itching, fever, aches, and headaches.

Little research studying interactions between CBD and common thyroid hormone replacement and anti-thyroid medications currently exists. 

CBD with Warfarin:

Warfarin, also known under the brand name Coumadin, is an anticoagulant (blood thinner) medication used to prevent the formation of harmful blood clots that could potentially cause heart attacks or strokes. Warfarin’s risks include severe bleeding, headaches, swelling, or sudden pain in extremities.

In 2017, researchers at the University of Alabama, Birmingham, conducted a study published in Epilepsy & Behavior Case Reports which showed that CBD increases the effects of drugs used for blood-thinning by slowing down how the body metabolizes warfarin and prolonging its presence in the system. By increasing the duration of warfarin’s presence in the body, CBD could potentially exacerbate some of the associated risks. 

Patients taking generic warfarin or Coumadin should consult their healthcare provider for individualized information and get blood tests before beginning a CBD regimen.

CBD with Eliquis:

Eliquis (generically called apixaban) is a blood thinner used to lower the risk of stroke or a blood clot in veins, the heart, the lungs, and the legs following knee or hip replacement surgery. 

Eliquis increases the risk of severe bleeding, and patients taking Eliquis are typically prescribed precise dosages by their doctor.

CYP proteins  in the liver process Eliquis, the same proteins on which CBD acts to delay metabolization.

This process could cause an overdose of Eliquis’ chemicals in the body and a high risk of severe bleeding making it prudent to speak to your doctor about your medications before taking CBD. 

CBD with Plavix:

Plavix is the brand name of the drug clopidogrel, frequently prescribed for patients who have had or are likely to have a heart attack. The drug works by blocking blood platelets from forming clots in arteries near the heart.

Research from a 2011 study published in the journal Life Sciences, says it is possible that CBD has an inhibitory effect on CYP2C19, the enzyme that metabolizes Plavix. This could cause Plavix to remain longer in the body and weaken its overall effects. Further research is required to determine whether this could lower Plavix’s effectiveness in preventing heart attacks. 

Patients using Plavix or clopidogrel should consult their physicians as to whether they should use CBD.

CBD with Metoprolol:

Metoprolol is a beta-blocker designed to treat high blood pressure by reducing the heart rate and changing the release of epinephrine, a hormone involved in stress and other processes. Beta-blockers lower blood pressure and sometimes produce side effects such as dizziness, nausea, stomach pain, heartburn, and cold hands and feet.

While zero studies have examined potential interactions between CBD and metoprolol, some placebo-controlled research conducted on healthy people at the University of Nottingham in England and published in 2017 in the journal JCI Insight has linked CBD with decreased blood pressure when taken on its own. 

For patients taking metoprolol, however, the combination with CBD could potentially affect blood pressure. 

Research from a 2011 study performed on mice and published in the British Journal of Pharmacology also shows that CBD has potential nausea-reducing properties, which may help soothe side effects associated with metoprolol. 

CBD with Metformin:

Metformin is a medication prescribed to adults with type 2 diabetes to help control blood sugar levels. Side effects of metformin include low blood sugar, nausea, diarrhea, vomiting, and muscle pain.

One 2006 study published in the journal Autoimmunity showed that CBD reduced the incidence of diabetes in animal models. 

Only one study, conducted by the American Diabetes Association and published in 2016 in the journal Diabetes Care, has examined the efficacy of CBD in patients with type 2 diabetes and found it had no significant impact on glucose levels.

Further research is needed on CBD’s interaction with diabetes. Patients taking metformin should talk to their doctor about whether CBD is right for them.

CBD with Statins:

Statins are a classification of drugs designed to lower cholesterol and protect against heart attack and stroke. Common side effects of statins are muscle soreness, blood sugar increase, headaches, and nausea. 

Statins are processed by CYP function in the liver, which CBD inhibits. While no research has specifically studied interactions between statins and CBD, the cannabinoid could potentially increase the strength and duration of statins in the system and the risk of unwanted side effects. 

What Other Drugs Should Not Be Taken With CBD?

CBD’s documented effects on liver function and enzymes that metabolize several medications play an important rule in drug interactions.  

Many of the prescription drugs not advisable to take in conjunction with CBD include a large percentage of existing prescriptions, such as benzodiazepines, antihistamines, haloperidol, antiretrovirals, statins, cyclosporine, sildenafil, warfarin, and other drugs metabolized by CYP3A4 and CYP2D6. 

Clobazam, used to treat epileptic seizures, is another type of drug that may not be advisable to take in conjunction with CBD. That being said, Epidiolex is an FDA-approved, CBD-based drug that physicians may prescribe to treat epilepsy although the drug can also cause adverse effects. This is based on a 2019 study conducted by researchers at Columbia University and published in the journal F1000Research. 

Disclaimer: You should always speak to their healthcare providers if they are considering taking CBD in combination with particular prescription medications.