Cannabis oil, the highs and lows of a potentially life-saving drug

Cannabis oil, the highs and lows of a potentially life-saving drug

Dr Simon Davis, specialist consultant, Express Medicals Ltd.

Over the past decade reports of the magical medicinal properties of cannabis oil have stimulated growing media attention.  Claims have been made about the oil’s ability to reduce pain, treat Parkinson’s disease and even cure cancer. Among all the claims and counter-claims there is a complex mix of a potentially life-saving treatment running headlong into political and legal inertia.

This has culminated in the recent heart rendering spectacle of families pleading for permission from the Home Office to allow the import and use of medical cannabis oil to treat their children’s life-threatening epileptic seizures. Yesterday, the Home Secretary announced that specialist doctors in the UK will be able to legally prescribe cannabis-derived medicinal products by autumn.

Those that meet safety and quality standards are to be made legal for patients with an “exceptional clinical need”, Sajid Javid said.

As it is a devolved matter, it will require legislative change before it is enforced in Northern Ireland

What is cannabis oil?

Cannabis oil is produced from extracts of the plant Cannabis sativa, commonly referred to as marijuana. The plant is pulped and the active ingredients recovered using a solvent extraction process. The end-product is a dark green viscous oil which is normally imbibed orally or rectally. Rectal administration is preferential as it results in a higher percentage of active ingredients being absorbed into the body.

Figure 1. Cannabis oil is a dark green viscous liquid often distributed in syringes.

The oil contains two active ingredients:



  1. The psychoactive tetrahydrocannabinol (THC) and
  2. The non-psychoactive cannabidiol (CBD).

The concentration of the two molecules is important due to their physical effects and the legality of their possession and use. When concentrations of THC fall below 0.2%, the use of the oil does not produce a ‘high’ in the person consuming it. In other words, the psychoactive effects of the compound are minimal or absent below this concentration. Due to the absence of a ‘high’ it is currently legal to possess, sell and use cannabis oil providing the THC content does not exceed the 0.2% threshold. This has resulted in a wide range of legal over-the-counter products becoming available within the UK.

Will I fail a drug test if I use cannabis oil?

Cannabis screening and drug testing normally depends on the presence of the THC metabolite 11-NOR-9-THC-9-COOH in a subject’s urine or oral fluid. Most testing programmes use a threshold concentration of equal or greater than 50ng per ml to determine if marijuana has been used by the test subject.

With THC concentrations of less than 0.2% (0.2 mg per ml) it would be highly unlikely that bodily concentrations of the metabolite could ever reach a value high enough to trigger a positive or presumptive positive test result. However, over the counter preparations are not pharmaceutical grade medicines and only have to conform with UK food safety standards. As a result, production quality may be variable, resulting in cannabis oil with unpredictable THC levels. It is, therefore, conceivable that oils could be mistakenly distributed with THC concentrations in-excess of 0.2 %.

As it is impossible to distinguish between positive results caused by poor production processes and deliberate marijuana use, it may be advisable to avoid cannabis oil may be advisable unless you are confident of the products THC concentration.

Does cannabis oil have medicinal properties?

Due to the psychoactive effects of THC, clinical studies have focused on CBD medications. At the beginning of this year, medical publication the Lancet published a US-based study highlighting the exciting potential for the application of this approach. The study investigated the effects of CBD administration on suffers of the debilitating form of epilepsy known as Lennox-Gastaut syndrome. The study reported a reduction in seizures, relative to a placebo group, of nearly 20%. This is statistically significant and could greatly improve the quality of life of those suffering from the syndrome. The paediatric research group at Massachusetts General Hospital has now entered the next phase of the study to identify any possible long-term side effects caused by prolonged CBD administration.

More startling results were reported on the effects of seizures experienced by Dravet syndrome sufferers. The Epilepsy Society Journal in late 2017 reported that the use of CBD reduced seizures in a 6-year-old child from 300 per month to fewer than 3. This is particularly significant as the child had become resistant to other forms of anti-seizure medications and had no alternative forms of treatment.

Although this limited research shows great promise, the use of CBD alone is not effective in all cases. Certain individuals appear to respond to cannabis oil only when it contains both CBD and THC at levels greater than 0.2%. This means the cannabis oil preparations used by such individuals may require THC concentrations sufficient to result in psychoactive effects.

This appears to be the true in the case of 12-year-old Billy Caldwell recently made the news when his medicinal cannabis oil preparation was confiscated by customs when he entered the UK. Billy is one of the individuals who is non-responsive to CBD alone and requires a preparation which combines CBD with low levels of THC in-order-to control his seizures. Although the concentration of THC was low enough to prevent any obvious psychoactive effects it was above the legal threshold of 0.2%. This was sufficient for customs to confiscate the preparation as the family entered the UK.

Why was it illegal to prescribe cannabis oil to treat seizures?

You may note that the studies referred to in this article have taken place outside the UK, this is not a coincidence. UK researchers had been frustrated by the ‘Catch 22’ scenario created by British regulations and drug classification. Currently psychoactive drugs with known clinical benefits are classed as Schedule 2. This includes powerful compounds such as Heroin (diamorphine), morphine and cocaine. Schedule 2 compounds can be prescribed by doctors to patients if they can demonstrate a clinical need. Researchers can also administer these drugs as part of research programmes and clinical trials. Compounds that are psychoactive but have no proven clinical benefit are classed as Schedule 1, this includes LSD and cannabis. Schedule 1 compounds cannot be prescribed by doctors or used in clinical trials without a specific Home Office licence. Such c are rarely issued. Thus, as cannabis oil has no clinical evidence of efficacy researchers are effectively barred from carrying out clinical trials to determine if there is any clinical efficacy.

UK researchers in this area are further frustrated by clear contradictions in current UK legislation. This is highlighted by the example of cannabis-based drug Sativex. Despite containing high levels of THC (around 50%) it can be legally prescribed by UK Doctors to treat MS and used in clinical trial without a Home Office licence. The obvious question is how can Sativex be legally used whilst Billy Caldwell’s oil preparation remains illegal? The answer is quite simple, in April 2013 the Home Office arbitrarily changed the classification of Sativex from Schedule 1 to Schedule 4. This resulted in the absurd position that THC now straddles more than one drug schedule classification.

Further contradictions and confusion in the legislation exist. For example, if you are a European resident in a country where medicinal cannabis is permitted, you can legally import prescribed cannabis oil with high THC concentrations under article 75 of the Schengen agreement. This means that a German child sitting next to Bill Caldwell could have legally walked through UK customs with the same cannabis oil confiscated from Billy’s mother.

The obvious contradictions and confusion in the current UK law have combined with growing public pressure. This resulted in an announcement by the Home Secretary that the Home Office will undertake an urgent review into current legislation surrounding medical cannabis and their associated preparations, and yesterday’s announcement.