Some of the most common medications that are affected by CBD include antidepressants, blood pressure medications and anti-seizure medications. It is always advisable to talk to a doctor about the risks and side effects before taking any new medication - this is especially important when taking CBD too.
CBD can increase the side effects of medications
Although CBD is generally considered safe, it can cause some side effects. These include:
- dry mouth
- liver damage (in extremely rare cases).
Taking CBD with other medications that have similar side effects may increase the risk of unwanted symptoms or potential poisoning. Taking CBD at the same time as over-the-counter and prescription medications that cause drowsiness, such as opioids, antipsychotics, antidepressants and antihistamines, can lead to increased drowsiness, fatigue and possibly accidental falls.
CBD may alter the effects of other medications
Many medicines are broken down by enzymes in the liver.
CBD inhibits the enzyme cytochrome P450, which is responsible for the breakdown of many prescription drugs in the liver. Consequently, taking CBD at the same time as medications that are metabolised by this enzyme can lead to increased drug levels in the blood and increase the risk of side effects.
Researchers at Penn State College of Medicine evaluated the available information on five prescription drugs that contain cannabinoids: Anti-nausea drugs used during cancer treatment (Marinol, Syndros, Cesamet); a drug used primarily for muscle spasms in multiple sclerosis (Sativex); and a drug for seizure disorders (Epidiolex).
The researchers drew up a list of 57 drugs for which a change in concentration can be dangerous. The list includes a variety of drugs, from heart medications to antibiotics, that can be affected by CBD or THC.
Do all forms of CBD interact with medications?
No. The faster and more efficiently CBD is absorbed into the bloodstream, the more likely it is to interact with medications.
For example, CBD enters the bloodstream most quickly through vaping or smoking and reaches a high concentration within 30 minutes, increasing the risk of acute side effects.
CBD oil taken sublingually is absorbed moderately quickly, but not as quickly as vaping, which reduces the risk of interactions.
In the case of foods fortified with CBD, the CBD takes significantly longer to be absorbed and it is less likely that a high concentration will be reached. Nevertheless, even here the concentration may eventually be high enough to cause problems or interact with other medications.
CBD for topical use, such as creams and lotions, does not usually enter the blood in sufficient quantities to interact with other medications.
What is the "grapefruit test"?
Some people use the so-called "grapefruit test" as a guide to avoid CBD if their medication has a grapefruit warning on the label.
More than 85 medicines have interactions with grapefruit and other citrus fruits such as oranges, grapefruit and tangelos. This is because chemicals in grapefruit known as furanocoumarins inhibit CYP3A4 in a similar way to CBD. The result is slower metabolism of drugs.
Grapefruit warnings are common with various medications, such as:
- Antibiotics and antimicrobials
- Cancer drugs
- Antiepileptic drugs
- Blood pressure medicines
- Blood thinners
- Cholesterol medicines
- Pain medications
- Prostate medications
While this is not an official way to find out if your medications interact with CBD, it can provide a first clue in any case.
How to take CBD safely while using medication at the same time
Talk to your doctor about it first if you want to try CBD as an add-on therapy to relieve the symptoms of a particular condition.
He or she can help you find the right CBD product and dosage and make sure you can take it safely with your medications. In certain situations, your doctor may monitor the blood plasma levels of certain medications you are taking.
Under no circumstances should you stop taking your medication to try CBD - be sure to check with your doctor before doing so.