Research conducted with CBD indicates that it has a good safety profile, but it interacts with some commonly prescribed drugs. As a result, the Food Standards Agency recommends that you shouldn’t use it if you’re taking medication.
Note: If you use any medication, you should consult your pharmacist or doctor before taking CBD. We are not medical professionals, and this article doesn’t contain an exhaustive list of the medications that shouldn’t be consumed with CBD.
When you take a medication, pharmacists and doctors have carefully set the dosage to produce specific, safe results. In some cases, CBD can change how a prescribed drug behaves in your body and even alter the amount that reaches your blood stream. This could produce unexpected results or side effects.
There are many drugs that may behave differently when taken alongside CBD, but some of the main groups include:
Medicines used to prevent blood clots may be more potent if taken with CBD. Studies conducted with warfarin concluded that this interaction might increase the potency of the drug, which could increase the risk of bleeding. The same interaction will likely occur with other anti-coagulants.
Anti-convulsants are commonly used to treat seizures or some types of nerve pain. Significant interactions have been noted with several of these drugs. UK Medicines Information (UKMI) particularly highlight clobazam and phenytoin as producing increased blood concentrations and related side effects when taken with CBD.
Not all antibiotics are known to interact with CBD, but those that have been reported include clarithromycin, erythromycin, and rifampicin. For them to be effective they must be taken in the precise measures prescribed by doctors; CBD could alter the amount that reaches your blood resulting in unplanned results.
Some modern antidepressants are likely to interact significantly with CBD if taken at a similar time. In some cases, it may increase the concentration of the medication and in others, it may boost the strength of the CBD. This may not seem like a negative, but it could be unexpected and produce side effects you’d not previously been aware of.
Some oral antifungal medications, such as ketoconazole, have been found, in some cases, to increase the concentration of CBD in your bloodstream by up to 89%.
Research conducted with CBD indicates that if beta blockers and CBD are taken together, they may cause a significant drop in blood pressure. Low blood pressure could cause fainting, dizziness, and an increase in the risk of falls for old people.
Current research indicates that the medications most likely to produce negative effects when taken with CBD are those that are metabolised by the cytochrome P450 family of enzymes or those that produce similar effects to CBD:
Cytochrome P450 enzymes are found in your liver. Some of them break down drugs to prevent them from causing harm. When a pharmaceutical drug is designed, pharmacists calculate how much of the drug will be destroyed by P450 enzymes and how much will remain in your blood. This means that you should have the intended amount of the drug in your blood after it’s passed through the liver.
However, when you take CBD, it binds with these enzymes and prevents them from working. The result is that a higher, possibly unsafe, concentration of the medication reaches your blood.
Another way that this could cause unexpected effects is if you take a medication that is also able to bind with cytochrome P450 enzymes. If this happens before the CBD reaches your liver, there will likely be a higher concentration of it in your blood.
Grapefruit juice also binds with cytochrome P450 enzymes and produces a similar effect to CBD if taken with some medication. Drugs that are likely to be affected by this interaction often come with a ‘grapefruit warning’ on the label. If you use a medication with this warning, it will interact with P450 enzymes and you should not consume CBD.
Currently, the mechanisms described here are the most common cause of medications interacting with CBD, but it’s likely that they’re not the only ones. Although lots of scientific studies have been conducted, there is still a lot to learn about how this cannabinoid interacts with the human body.
The medications mentioned in this article are just examples; the list above is not exhaustive. If you use any medication, you should consult your pharmacist or doctor before taking CBD.
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We are a small but mighty team of experienced natural health researchers. We follow strict selection criteria and test everything we retail: from ground-breaking food supplements to natural skincare products. Our main area of expertise is CBD.