Clinical interest in medical cannabis is steadily growing all around the world; however, there remains a broad lack of education and, often, misinformation on the subject. 
Cannabis is heavily represented through politics and media as a potentially harmful recreational drug. But this plant has a much more complex and well-investigated history than most people understand. Take a look at this introduction to medical cannabis to learn more about this fascinating plant.
A Brief History of Medical Cannabis
Evidence of cannabis being used as a medicine dates back thousands of years. Several discoveries suggest that ancient societies, including the Ancient Egyptians, Greeks, and Chinese made use of the plant as an anaesthetic, an anti-epileptic, and for general pain relief. 
Archaeological research shows that the human cultivation of the cannabis plant originated in Southeast Asia around 12,000 years ago. The crop was initially used as a foodstuff and for craft, such as to make ropes, clothing, and weapons. The medicinal value of cannabis soon became apparent, leading to a more diverse utilisation of the plant. Cultivation of cannabis began to spread westward, starting in the Middle East, before spreading to Europe, and eventually, the Americas. 
People in Britain have cultivated hemp (low-THC cannabis) since the late 16th century (King Henry VIII even dictated that all farmers dedicate a quarter of an acre to the crop). However, the medicinal use of the plant didn’t gain much traction in Britain until the 19th century. Irish physician William O’Shaughnessy, having carried out research in India that demonstrated the medicinal potential of the plant, endorsed its use for the management of a number of symptoms and conditions, including chronic pain, epilepsy and nausea and vomiting associated with cholera.
After around a century in wide circulation across Europe and the Americas, concern around the recreational use of cannabis, heavily conflated with an epidemic of opioid abuse, prompted the longstanding prohibition of the plant.
The Recent History of Medical Cannabis in the UK
Prohibitions on cannabis and a number of other substances began to emerge in various countries in the early 20th Century, leading to the 1961 UN Single Convention on Narcotic Drugs. In the UK, this led to the Misuse of Drugs Act in 1971, which placed a restrictive classification on cannabis, effectively resulting in the prohibition of all its forms.
Following almost half a century of prohibition, the UK government eventually legalised the medical use of cannabis in November 2018,. This decision, alongside a growing body of evidence to support the efficacy of medical cannabis in treating specific conditions, was heavily influenced by a number of highly publicised cases of intractable paediatric epilepsy.
The families of these young patients, having observed dramatic improvements in their children’s condition with the help of medical cannabis products, especially as compared to the results achieved with potent frontline medicines, successfully appealed to the government to enact the law change.
Despite this change, however, access remains difficult for many patients in the UK. The vast majority of medical cannabis prescriptions are carried out through private clinics. The NHS, under NICE guidance, has only made limited recommendations for the use of cannabis-based medical products (CBMPs) for a small number of indications. 
Who can be prescribed medical cannabis?
While access to medical cannabis through the NHS is heavily limited, the list of eligible conditions for a medical cannabis prescription through private care is more extensive. The most common reason for medical cannabis prescriptions in the UK to date is to manage chronic pain conditions, which is consistent in countries all over the world.
Other conditions that may be eligible for a medical cannabis prescription include (but are not limited to):
- Chemotherapy-induced vomiting and nausea
- Sleep Disorders
- Headaches and migraine
- Palliative care
- Diabetic neuropathy
Types of Medical Cannabis Products
There are several types of medical cannabis products available for prescription in the UK. These can vary from whole flower and full-spectrum extracts to isolated, synthetic cannabinoids.
Clinicians in the UK use a number of variables to determine the most suitable medical cannabis product for each prescription. The condition in question, as well as the characteristics of each patient, including age, health, and tolerance are all important factors.
Aside from cannabinoid content, the form of the product and the method of ingestion is determined based on highest efficacy for the condition at hand. For example, gastro patients will likely be prescribed oils to ensure direct bioavailability through ingestion. Conversely, a chronic pain patient may prefer vaporised whole flower cannabis as this provides a faster onset analgesic effect than ingestion. 
Prescribers will often initiate medical cannabis treatment using products with a low or no THC ratio to avoid unnecessary side effects, potentially introducing a low THC ratio and slowly increasing this until a desired clinical response is observed. This is informally referred to as the “start low, go slow” protocol.
Cannabis flower refers to the whole plant product consisting of the dried/cured leaves and/or buds of the cannabis plant. These medical cannabis products are the most commonly prescribed globally. While medical cannabis flowers are much the same as recreational cannabis, the plants are cultivated to much higher and stricter standards to ensure safety and quality.
Medical cannabis flowers must be vaporised, as aside from smoking being against any clinical recommendation, it remains illegal to smoke cannabis, even for medicinal purposes.
Cannabis oils are a category of medical cannabis products that are usually designed to be administered sublingually (under-the-tongue). These products contain varying quantities of cannabinoids, alongside other cannabis compounds and carrier oils.
When using cannabis oils, the cannabinoids and other active ingredients are absorbed through the thin layer of skin under the tongue and into the bloodstream.
Topical medical cannabis products are usually prescribed for the treatment of conditions where symptoms can be treated locally. For example, dermatological conditions and some pain conditions such as musculoskeletal pain and arthritis.
These products are currently in a limited category of clinical use, as aside from CBD, cannabinoids administered transdermally appear to have lesser bioavailability than other routes. 
Cannabis vaporisers are designed to heat, and thereby decarboxylate, the cannabinoids present in the flower in a controlled manner. This allows cannabinoids and other active ingredients – such as terpenes and flavonoids – to be absorbed into the bloodstream via the lungs.
Vaporising cannabis means that cannabinoids can be absorbed at much lower temperatures. This avoids the intake of carcinogens, tars, and harmful burnt plant material.
How is Medical Cannabis Made?
The methods used to produce medical cannabis products vary significantly depending on the intended purpose, ingredients, and form of the final medicine. For example, medical-grade cannabis flowers are cultivated in much the same way as many other cannabis crops. However, this process is tightly monitored and regulated to ensure high quality, consistency, and the prevention of contamination.
This is also true of cannabis grown for the production of other forms of medicine. However, products such as oils and topicals will require many more steps before the final product is achieved. These steps include extraction of the required compounds, distillation and purification, and combination with other ingredients.
There are currently only two medical cannabis products that have been licensed for use in the UK: Epidyolex (CBD) and Sativex (THC:CBD). However, unlicensed products can be prescribed by specialist clinicians for a variety of conditions.
While these medical cannabis products are currently unlicensed, they must still be produced to the same standards as licensed products. In order to be supplied in the UK and EU, medicines must be GMP (Good Manufacturing Practice)-certified.
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