Research conducted with CBD indicates that it has a good safety profile for healthy adults. However, if you are taking commonly prescribed drugs, it could be a different story. The Food Standards Agency recommends that you shouldn’t use CBD at all if you are 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. If in doubt, stop taking CBD and speak to your GP or pharmacist.
Many drugs may behave differently when taken alongside CBD, but some of the main groups include:
Around 60% of all prescription medications are processed using the same enzymes that process CBD. This means that interaction is highly likely. If you are taking prescription medication, it’s a good idea to check with your pharmacist or GP to confirm if it is safe to add CBD to your daily routine.
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 bloodstream. This could produce unexpected results or side effects. Medications could also alter the way your body processes CBD, leading to higher levels in your bloodstream.
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 these antibiotics to be effective, they must be taken in the precise measures prescribed by doctors. CBD could alter the amount that reaches your blood, which could make them less effective.
Some modern antidepressants are likely to interact significantly with CBD if taken at a similar time. Examples of antidepressants that should not be taken with CBD include sertraline and citalopram. If you are using a different brand, consult with your GP before adding CBD to your routine.
In some cases, CBD 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%. This could result in you taking more CBD than you need to and experiencing adverse side effects as a result.
Benzodiazepines like Valium or Xanax are commonly used to treat anxiety and panic disorders. CBD can slow the metabolism of this category of medication, leading to higher concentrations in your bloodstream.
Since benzodiazepines produce a sedative effect, taking it alongside CBD could increase the efficacy of the drug. This could lead to increased drowsiness, reduced motor function, impaired reaction times, lightheadedness, and fainting. It could also mean that the medication takes longer to wear off, so you might feel the effects for longer.
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 older 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 building up in your body and 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 allows them to determine the right dosage and schedule for optimum results.
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.
And finally, some of these medications produce side effects that are very similar to the side effects of taking too much CBD. This makes it more difficult to determine if you’re taking too much of your medication or too much CBD.
Grapefruit juice also binds with cytochrome P450 enzymes and produces a similar effect to CBD if taken with some medications. Drugs that are likely to be affected by this interaction often come with a ‘grapefruit warning’ on the label.
Since CBD is quite new to the market, the label might not include information about a potential interaction. However, if you notice a grapefruit warning on your medication, this means that it will interact with P450 enzymes. In this case, you should skip CBD as long as you are taking the medication.
CBD is certainly capable of interacting with lots of different medications. This can be dangerous for multiple reasons, so it’s important to be aware of potential interactions before you add CBD to your daily routine.
Although lots of scientific studies have been conducted, there is still a lot to learn about how CBD interacts with the human body and how it interacts with other medications. There is unlikely to be a warning on your medication label, so you need to be aware of the risks.
The medications mentioned in this article are just examples and the list above is not exhaustive. If you use any medication, you should consult your pharmacist or doctor before taking CBD. If you see a “grapefruit warning” on your medication, this is a good indicator that it is not safe to take it alongside CBD.
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