Side effects and safety of medicinal cannabis
The products that are included in the pilot programme have not been studied in the same systematic way as the method used for authorised medicines. This means, among other things, that the scientific evidence of side effects is very limited.
It is very important that doctors and patients report all suspected side effects of medicinal cannabis to the Danish Medicines Agency so we can learn more about how the different products affect the body.
What we know about side effects of THC and CBD
The knowledge that the Danish Medicines Agency currently has about side effects of medicinal cannabis is primarily based on international clinical studies of cannabis-based medicines such as Sativex, Cesamet/Nabilone and Marinol.
Some of the side effects of THC-containing products are: sleepiness, dizziness, mood changes, anxiety, concentration and memory problems, low blood pressure causing fainting, and effects on the ability to drive. Among the more serious psychiatric symptoms are depression, hallucinations, paranoia, delusions and suicidal thoughts. If you use THC-containing products for longer periods, you are at risk of developing dependence. This has been seen when patients with chronic pain are treated with medicinal cannabis. When it comes to long term use, the knowledge of side effects is generally limited, but it cannot be ruled out that concentration and learning ability are negatively affected.
There is only very limited knowledge about the side effects caused by CBD. There is evidence that CBD may affect the liver and possibly also the immune system.
You can find more information about warnings and side effects related to medicinal cannabis in the guidelines for doctors (in Danish only).
Report all side effects of medicinal cannabis
Doctors have a duty to report all suspected side effects of cannabis products comprised by the pilot programme to the Danish Medicines Agency (except suspected side effects that are caused by medication errors). Patients and relatives can report suspected side effects to the Danish Medicines Agency.
We would like to encourage all patients who experience side effects from medicinal cannabis to tell their doctor and to report the side effects to the Danish Medicines Agency. You do not have to be sure that it is the medicinal cannabis you are taking that is causing the symptoms to make a report – that you suspect the product to be the cause is enough.
We collect side effect reports (sometimes called adverse reaction report or ADR reports) to find out if there are signals of new or changed risks in relation to the cannabis products of the pilot programme. The ADR reports are part of the basis we use to regularly assess the safety of the products.