Study reveals significant variation in cannabis content in doctor-prescribed tea

When patients brew a cup of tea with the recommended dose of medicinal cannabis, the actual dose of active ingredients they ingest can vary significantly.

This is shown in a new study from the Department of Forensic Medicine at Aarhus University, recently published in the scientific journal Basic & Clinical Pharmacology & Toxicology.

The study examines the doses of THC, THCA, CBD, and CBDA in tea brewed from three different medicinal cannabis products that are part of the medicinal cannabis pilot program in Denmark.

Since 2018, Danish doctors have had the opportunity to prescribe a new type of cannabis product that was previously illegal in Denmark. This prompted researchers from Aarhus University to investigate the doses patients are exposed to when preparing the medicine as tea at home, following the manufacturer’s recipe.

The study shows that treatment with the recommended starting dose of 0.2 liters of tea made from three different cannabis products can result in very low doses with the product Bediol and overdosing with the product Bedrocan if aiming for THC starting doses comparable to the approved medication Sativex, used for patients with multiple sclerosis.

"It is surprising that the content of active substances varies significantly when the recommended starting dose for the three different products is the same," says physician and Ph.D. student Marie Bach Sønderskov, one of the researchers behind the study.

If patients receive the wrong THC dose, they may either experience no effect at too low a dose or feel intoxicated and dizzy at too high a dose.

Day-to-day differences

The researchers hope the study can help doctors assess which cannabis product might be prescribed. The products in the medicinal cannabis pilot program have not been tested in clinical trials, meaning that doctors do not have the same knowledge about effects and side effects as they do with approved medications. This also means that the doctor must take full responsibility and, for example, determine the correct dosage for each patient.

However, the Danish Medicines Agency has provided guidelines for doctors to consult if they consider prescribing medicinal cannabis.

"When doctors prescribe medicine, the content is usually very precisely defined. But in dried plant products, which the patient can brew as tea or inhale, it is uncertain how much of the active substances are present. We can see that if you start with the recommended amount of the product with the highest THC content, you can receive quite a high dose," explains Marie Bach Sønderskov.

"The study emphasizes that caution is needed when using cannabis tea because there is uncertainty about the actual dose in the tea," she says.

Even when patients use the same cannabis product and the same recipe, the study shows that the tea's content can vary from batch to batch. This may be due to fluctuations in temperature or the concentration of active ingredients in the cannabis product in one random dose compared to another.

"We even weighed the cannabis product with a very accurate scale, making the process even more standardized than what you would expect at home," says Marie Bach Sønderskov.

The study also indicates that there is no reason to choose cannabis tea based on the amount of terpenes, which contribute to the aroma and flavor. Once the tea is consumed, there are no terpenes left — they have evaporated.

Watch out for the cream

When patients brew tea for multiple days, it is recommended to add coffee cream after brewing to stabilize the tea. But the timing of adding the cream is critical.

The study shows that adding cream to the tea before boiling, instead of afterward as recommended, increases the average THC and CBD dose by 2.1-4.4 times.

"This happens because the substances are fat-soluble. There is simply a higher concentration of THC and CBD in the tea when fat is added during boiling," explains Marie Bach Sønderskov.

She emphasizes that it would be interesting to conduct clinical trials on the effects of these products, but it is currently not feasible to conduct clinical trials with medicinal cannabis in Denmark, even though its use is a growing trend worldwide, as there is not the same knowledge about these products as there is for approved medications.

The Danish Medicines Agency has previously stated that medicinal cannabis should only be considered in cases where there is some evidence that medicinal cannabis may have an effect—for example, in cases of painful spasms due to multiple sclerosis or spinal cord injury, nausea after chemotherapy, or pain caused by disease in the brain, spinal cord, or nerves.

Facts: The Medicinal cannabis pilot program

• Since January 1, 2018, doctors in Denmark have been allowed to prescribe a new type of cannabis product that was previously illegal in Denmark.
• The products included in the pilot program can take the form of, for example, dried cannabis flowers, cannabis oil, capsules, or tablets.
• Medicinal cannabis is not approved as a medicine but must meet several requirements, including how the plant should be cultivated and how the production of the cannabis product is carried out. There are also requirements for the cannabis product to be standardized. This means that the manufacturer must be able to document the product's content so that the strength and quantity are consistent from batch to batch.
• During the trial period, the program will be evaluated to determine if it should be made permanent. The period runs until December 31, 2025.

Source: Danish Medicines Agency

About the Research

• The study measured concentrations of cannabinoids and terpenes in cannabis plant products and tea. The researchers compared the concentrations in tea made with different cannabis plant products and different preparation methods.
• Collaborators include Rime Bahij from the Department of Green Technology, University of Southern Denmark, and Jørgen Bo Hasselstrøm from the Department of Forensic Medicine, Aarhus University.
• External funding: The Medicine Fund of the Danish Regions , the Health Foundation, the A.P. Møller Foundation, and the Health Research Foundation of Central Denmark Region .
• Read more in the scientific article: https://onlinelibrary.wiley.com/doi/10.1111/bcpt.14056

Contact Information

Physician and Ph.D. student Marie Bach Sønderskov
Aarhus University, Department of Biomedicine and Aarhus University Hospital, Clinical Pharmacology
Phone: +45 29 44 26 99
Email: mbn@biomed.au.dk

Clinical Lecturer and Senior Physician Charlotte Uggerhøj Andersen
Aarhus University, Department of Forensic Medicine and Aarhus University Hospital, Clinical Pharmacology
Phone: +45 60 12 84 30
Email: cua@forens.au.dk

Sales data for different types of cannabis medicine in Denmark

Source: medstat.dk