CBD and Medication – Interactions

CBD and drugs: thanks to the growing number of studies in existence, researchers now know many of the effects of the CBD, an active constituent derived from the hemp plant. However, as in the case of research into other known active substances, cannabidiol research has “only” been carried out seriously for about 40 years – ever since it became known that it can be used to treat many medical conditions, and that it can also be used preventively. Compared with other substances which are known to have a positive influence on the human body, this is certainly a relatively short period. This area of research, which concerns itself with interactions between CBD and other medication, is thus still young, and new discoveries are being made all the time.

It should be noted that the term “interaction” here refers to something akin to that which is meant by the term “drug interaction”. Taking various different active substances or drugs at the same time, a phenomenon referred to as polymedication, can lead to undesired or unexpected pharmacological effects. These can include the strengthening, weakening or even the nullification of the desired effects.

Can interactions between CBD and medication occur?

An indirect interaction between CBD and medication has to do with the breakdown of medication. CBD inhibits specific enzymes (such as CYP2D6 and CYP2C19). These are, however, responsible for the breakdown of many pharmacological agents in the body, and so the interaction may result in the concentration of the medication in the bloodstream remaining unusually high beyond the intended period.

Although this can also have positive effects, for example if you want to prolong the duration of the effect of some kind of medication without increasing the dose, it can also increase the risk of harm occurring as the result of an unintended overdose.

In general, it can be said that there are hardly any CBD interactions, however, some have been proven. We recommend: Always consult your doctor if you are taking any strong medications.

CBD influences enzymes

By influencing the enzymes CYP3A4, CYP2C9, CYP2C19 and CYP2D6, CBD can cause further interactions to occur.

• CBD’s inhibition of CYP3A4[1] for example, could alter the effects of antidepressants such as Trazodon.
• The combined effect of CBD in combination with medication on the enzyme CYP2C19[2] can impair the ability of ticlopidine to inhibit platelet aggregation.
• If CBD acts on the enzyme CYP2C9[3] this could, among other things, alter the efficacy of torasemide as a loop diuretic.
• The effects of CBD on CYP2D6[4] could result in the alteration of tetrabenazine’s neuroleptic effects.

These risks also exist when consuming CBD in combination with drugs.

Drug interactions (THC)

Studies have shown that CBD is an antagonist of the psychoactive substance THC (both of which are derived from the hemp plant). For example, taking CBD after smoking THC will reduce or even completely inhibit the effect of the THC.

On the other hand, if taken before consuming THC, CBD can even enhance its effects.

The same applies to other medication. The reason for this is that THC is broken down by the same enzyme that breaks down other medication, and this enzyme is supressed by CBD. The use of CBD can result in undesirable interactions in the case of the cytotoxic drugs used in chemotherapy.

As already mentioned, CBD inhibits the enzyme P450. Amongst other things, it is the reason that the dosage of powerful chemotherapy drugs needs to be so high, because it breaks such medication down. However, if the enzyme can no longer fulfil this task because CBD is present, the dose of cytostatic drugs in the blood increases to a fatal level. 

What medication should not be taken in combination with CBD?

Certain types of medication, when taken over longer periods, can have a harmful effect on the human body due to their inhibition of the P450 enzyme. Medical specialists know that CBD should not be taken at the same time as these, as the danger of such an interaction constitutes a risk which is simply not worth taking.

For those already taking medication, the use of CBD should be monitored very closely. Many doctors advise their patients that, after taking medication, they should wait at least 2h before taking CBD.

Generally speaking, cannabidiol interacts with the following medicines:

• beta blockers
• statins
• anticonvulsants
• antibiotics
• anticoagulants
• anti-inflammatory
• painkillers
• steroids
• antipsychotics
• antidepressants
• benzodiazepine

Below we have listed the most common CBD and drug interactions:

Medication	Explanation of the interaction
ibuprofen	According to current research, interactions between CBD and painkillers from the group of non-steroidal anti-inflammatory drugs (NSAIDs), to which ibuprofen also belongs, are possible. Cannabidiol has a similar effect as grapefruit. Namely, various enzymes in the liver are influenced that are responsible for the degradation of ibuprofen in the body (the so-called cytochrome P450 enzyme system). In this way, CBD can enhance the effect of ibuprofen. This in turn can lead to a lower dose of the painkiller having to be taken. It is also possible that taking ibuprofen and CBD together increases blood pressure.
pill	Some active substances in both the pill and CBD are broken down in the liver. Caution is therefore advisable, at least with oestrogen preparations, as taking them together can lead to a reduction in the contraceptive effect. If in doubt, consult your gynaecologist. According to current studies, the risk of interaction between CBD and the pill is lower if the latter contains progesterone instead of oestrogen. Again, if in doubt, ask your doctor.
L-thyroxine	CBD can support the treatment of thyroid disorders in different ways. In the case of hypothyroidism, the body is supplied with thyroid hormones in the form of L-thyroxine. Initial study results suggest that CBD may have a beneficial effect on this treatment. CBD apparently regulates the release of thyroid hormones and is thus basically suitable as a supplement to treatment with L-thyroxine. However, the treatment should be monitored by a doctor.
antibiotics	So far, there is no evidence that taking CBD at the same time as antibiotics has negative effects. At the same time, studies indicate that cannabidiol itself has antibacterial effects and can thus support the effect of antibiotics. However, it is in no way suitable as a substitute for antibiotics in the case of an acute bacterial infection.
St. John’s wort	CBD is considered a useful supplement to treatment with St. John’s wort. Both mechanisms of action complement each other well, especially when St. John’s wort is used against depressive moods. St. John’s wort has a mood-lifting effect, while CBD has a calming and sleep-promoting effect. Even though no negative interactions are known so far, the joint intake should be discussed with the doctor.
citalopram	The joint use of citalopram and CBD has not been particularly well studied. It is considered certain that CBD also inhibits the breakdown of the drug by the liver in this case. This can have an effect on the dosage. However, no noteworthy or even harmful interactions have been reported so far. Since both active substances increase the serotonin content in the brain, there is a certain risk of mania. Taking CBD together with other drugs should therefore be discussed with the doctor in charge.
alcohol	Interactions between cannabidiol and alcohol are common. Excessive alcohol consumption in particular can cause the combination with CBD to lead to nausea, cardiovascular problems and psychological problems. For this reason, the joint use of alcohol and CBD is strongly discouraged. This is especially true when both are used in large amounts and in high concentrations.
psychotropic drugs	The question of interactions between CBD and psychotropic drugs cannot be answered in a general way, as this is a very large group of active substances. A joint use of antidepressants and CBD, for example, cannot be ruled out in principle. However, a distinction must be made between selective serotonin reuptake inhibitors (SSRIs) – e.g. citalopram – and so-called tricyclic antidepressants. With the latter, CBD can enhance the calming and blood pressure-lowering effect. The following applies to all psychotropic drugs: They should only be taken together under medical supervision, if at all. This applies especially to neuroleptics.

Discussing contraindications of CBD with your doctor

Around 470 million prescriptions are issued in Germany every year. In the case of two percent of these prescriptions, i.e. 9.4 million of them, problems occur as a consequence of the medication patients are prescribed. Many of these problems could be avoided if patients checked package inserts more thoroughly for possible side effects and interactions,  as well as by informing the doctors issuing the prescription of all the substances they were taking, for example.

This knowledge, combined with the patient’s personal history can, even in the case of CBD, be identified as a contraindication on consultation with a doctor. This means that having taken a substance in the past makes it impossible to be given the treatment or therapy which is considered necessary. In such cases, doctors distinguish between absolute and relative contraindications. In the case of absolute contraindication, certain medical measures are rigorously prohibited. In the case of relative contraindication, certain additional treatments and therapies are only approved under strict conditions, once all the risks have been weighed up. 

As described above, CBD interacts with the enzymes involved in the breakdown of active substances. If, therefore, this process of breakdown is not to be disturbed, following consultation with a doctor, the CBD contraindication should be taken very seriously. If such a contraindication is ignored, considerable damage to the health of the patient can result.

Ultimately, in the case of all substances which influence the body, it is always a good idea to consult a trusted specialist before taking them in order to discuss everything thoroughly.

A recent study[5] supports this kind of approach. In this study, the possible toxic effects of CBD on the liver were investigated. The research team found that the mice tested suffered liver damage within 24 hours. Specifically, the CBD drug Epidiolex was administered to the test animals. Whether this negative effect could also occur in humans was not established. Nevertheless, those behind the study advise those who suffer from alcoholism or a predisposition for liver damage to consult with their doctors thoroughly before taking CBD.

FAQ’s

Sources

[1] https://pgsbox.de/pharma-sensor/CYP3A4?fbclid=IwAR1yG3bIGzSN3yOXHpmdvyiJqNh87r1FFzlWdUn_HprRVi9GvqsVE67Q5oA – 24.09.2019

[2] https://pgsbox.de/pharma-sensor/CYP2C19?fbclid=IwAR00IyL2LAJjR4BHbSGnH-wdVTvq1R4DxXBd6UJ_9BN-CLPuX0IDy3IUKtI – 24.09.2019

[3] https://pgsbox.de/pharma-sensor/CYP2C9?fbclid=IwAR0lo27fr8Sw_cAkvnbbyukZ7lfu66iDndOlnYFf5mUxa3IX8Bu848kIrsQ – 24.09.2019

[4] https://pgsbox.de/pharma-sensor/CYP2D6?fbclid=IwAR1mURNkjYRVsPQ65mMO6ZrYxklvDr3e-WlhqLk_GbW8XNdN3AYOkFosUMs – 24.09.2019

[5] https://www.mdpi.com/1420-3049/24/9/1694 – 27.07.2019

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Taking products containing cannabinoids may result in interactions with various medications. If you are already taking medication, the use of CBD and other cannabinoids should be discussed with your doctor beforehand.