Cannabis' medical history
The history of cannabis
How a forbidden plant became medically recognised
The current scientific research and focus on cannabis as a medical preparation is a reinvention of an old drug using modern scientific methods
The first uses of cannabis
Cannabis has been cultivated and used by humans since at least 4000 BC. It was initially cultivated in China, primarily for use as food or as fibre for string, rope, textiles and paper. Cannabis was used for medicinal purposes in China, but medical use became more prevalent later in India, where it was also associated with religious rituals and recreational use. Cannabis subsequently spread to the rest of the world, including Europe. Still, during the 18th century the plant was primarily cultivated in Europe for fibre production, and there were fewer references to medicinal use[1,2].
Introduction to Western medicine
The actual introduction of cannabis into Western medicine came in the mid-19th century when doctors began to scientifically explore the therapeutic uses of cannabis and its euphoric effects. The use of cannabis as a medicine peaked in the second half of the 19th and early 20th century, and cannabis extracts and tinctures were marketed at this time by pharmaceutical companies such as Merck, Bristol-Meyers Squibb and Eli Lilly for sedative, analgesic and appetite-stimulating effects[1,2].
Cannabis as an illegal drug
The medical use of cannabis declined during the 20th century. One of the reasons for this may have been the wide variation in the content of different cannabis batches, making it difficult for patients to control the effects. In addition, synthetic medicines also gained market approval for many of the symptoms previously treated with cannabis. Legal restrictions on cannabis were also introduced during this period, limiting the use of cannabis for medical or scientific purposes. Despite this, recreational and illegal use of cannabis spread rapidly among younger people in the Western world in the 1960s, leading to the reputation that medical cannabis competes with today - mainly due to the uncontrolled breeding of plants to obtain the best recreational high[1,2].
These days, the majority of patients purchase their cannabis through illegal sources[3]. No proper control of potency or impurities exists, and the lack of medical advice poses additional risks. Therefore, doctors must be well educated on the use, dosage and safety of medical cannabis so they can guide patients towards legal prescriptions and proper and safe administration.
Cannabis is now accepted in Denmark.
The legal framework in Denmark allows for the medical use of cannabis products if the doctor has written a prescription for the patient and it is purchased at the pharmacy.
Four main categories of medical cannabis products in Denmark are available on prescription to seriously ill patients. These include[4]:
Authorised medicines have been through the official drug approval process and have therefore been tested in controlled laboratory studies, animal studies and human subjects. The companies have submitted all data from the trials to the authorities, who have assessed that the medicine’s benefits outweigh the risk of side effects.
Non-authorised medicines (dispensing authorisation) are cannabis products not authorised in Denmark, but the doctor can apply for a dispensing approval from the Danish Medicines Agency. Under this scheme, the medicine can be imported from, e.g. the USA and prescribed to specific patients if the Danish Medicines Agency approves the doctor's application.
Magistral manufacturing is products prepared in a pharmacy for a specific patient according to the doctor's instructions. Magistral manufacturing is a scheme created because some patients may have a particular need that cannot be met with regular authorised medicines.
Medicinal cannabis pilot programme (cannabis flowers and cannabis extracts) Since 1 January 2018, doctors in Denmark have been able to prescribe a new type of cannabis product under the medicinal cannabis pilot programme. This means that doctors can prescribe products that are neither authorised medicine nor magistrally produced medicine. The products can take the form of dried cannabis flowers, cannabis oil, capsules, tablets, etc.
Finished pharmaceutical products may contain synthetic cannabinoids, isolated cannabinoids or a broad spectrum of cannabinoids, terpenes, flavonoids, etc., derived from the plant. Cannabis flowers and many cannabis extracts/preparations (including medicinal cannabis) contain a broad spectrum of cannabinoids, terpenes, flavonoids, etc.
Criteria for prescribing medicinal cannabis
The responsibility for medical treatment with cannabis always lies with the treating physician. Therefore, it is the doctor who determines whether a patient should be treated with medicinal cannabis.
According to the cannabis guidelines from the Danish Medicines Agency [4]:
relevant authorised marketed medicines should be tested before treatment with medicinal cannabis is attempted
cannabis should not be used in children and adolescents under the age of 18 due to a lack of knowledge about long-term effects, including on cognitive development
a doctor can prescribe a maximum of one month's consumption on one prescription
doctors should not treat with medicinal cannabis outside their area of specialisation
The Danish Medicines Agency has assessed which patient groups and possible therapeutic indications could be relevant for treatment with medicinal cannabis[4]:
Chronic pain conditions
Pain is considered chronic for more than 3-6 months. Chronic pain conditions such as nerve pain (neurogenic or neuropathic pain) and cancer pain may be relevant to treat with medical cannabis for some types of patients. Medical cannabis can be prescribed by any doctor if there is a pain indication.
Multiple sclerosis
There are approved cannabinoid medications for patients with moderate to severe spasticity due to multiple sclerosis (MS) who do not benefit from other antispastic drugs. Central nerve pain and painful spasticity in MS may be appropriate to treat with medical cannabis, which a neurologist can prescribe.
Spinal cord injury
Spinal cord injury (paraplegia) is often associated with central nerve pain, painful spasticity and problems with bladder function. The Danish Medicines Agency assesses that treatment with medicinal cannabis may be relevant for spinal cord injuries. The prescription should be made by a neurologist.
Nausea and vomiting after chemotherapy
The Danish Medicines Agency assesses that nausea and vomiting during or after chemotherapy may be relevant to treat with medicinal cannabis. When treating cancer patients, the prescription should be made by a haematologist, oncologist or palliative care physician.
Therapeutic effect or not?
Large, randomised clinical trials investigating the efficacy and safety of medical cannabis for specific indications are still very limited. Therefore, claims of "no evidence" or "limited evidence" do not necessarily mean that reliable, well-designed studies have found "negative evidence" but rather that there is a lack of scientific data. Doctors rely heavily on their patients' feedback to assess effectiveness and side effects as part of a more personalised approach.
In a report based on a review of the literature, the National Academies of Sciences, Engineering and Medicine (USA) identified indications for which they find "substantial evidence" of efficacy for medical cannabis. These are primarily[5]:
Chronic pain in adults
Nausea and vomiting after chemotherapy
muscle cramps in patients with multiple sclerosis
When prescribing medicinal cannabis in Denmark, doctors have a stricter duty to provide information, as it is a medical treatment for which the clinical evidence for efficacy and side effects is not fully clarified[4].
Furthermore, there is no approved data available for medicinal cannabis, e.g. on the correlation between dosage and side effects, nor is there a summary of product characteristics or a package leaflet (unlike authorised medicines). It should also be noted that the use of cannabis is associated with side effects. Please refer to the precautions page and the FAQ page.
References
Pisanti, S. & Bifulco, M. Medical Cannabis: A plurimillennial history of an evergreen. Journal of Cellular Physiology vol. 234 8342–8351 (2019).
Zuardi, A. W. History of cannabis as a medicine: A review. Revista Brasileira de Psiquiatria vol. 28 153–157 (2006).
Kvamme, S. L., Pedersen, M. M., Alagem-Iversen, S. & Thylstrup, B. Beyond the high: Mapping patterns of use and motives for use of cannabis as medicine. Nordic Studies on Alcohol and Drugs 38, 270–292 (2021).
Danish Medicines Agency. Guidance on physicians’ treatment of patients with medical cannabis covered by the trial scheme. Retsinformation (2018).
The National Academies of Sciences Engineering and Medicine (U.S.) Committee on the health effects of marijuana: an evidence review and research agenda. The health effects of cannabis and cannabinoids: the current state of evidence and recommendations for research. Washington, DC: the National Academies Press (2017).