THCV - an abject cop-out from the ACMD, another research opportunity for the UK lost

By David Nutt

The cannabis plant produces over 100 compounds with therapeutic potential. Most of these have never been properly studied because of the complications of researching any cannabis plant extract that might contain d9THC, the “stoning” element of the “herb”. D9THC and many related compounds are controlled under the 1971 Misuse of Drugs Act [MDAct1971]. Here they are placed in Class B [drugs of moderate harm] alongside amphetamines, which means that supply can result in up to 14 years in prison.  In the same Act, they are also controlled as Schedule 1 drugs, alongside crack cocaine.  Drugs are put in Schedule 1 when the Home Office, guided by the ACMD, determine that they have no medicinal value. The fact that cannabis is in Schedule 1 when it was, until 1971, a licensed medicine and is now restored to that status in 18 countries and most American states is scientifically bewildering. Even more absurd is that a synthetic form of d9THC, dronabinol, is a licensed medicine and is in Schedule 2. 

Schedule 1 status is to drugs what Catch 22 is to military psychology. Drugs can only escape Schedule 1 if they can be demonstrated to have medicinal value yet because they are in Schedule 1 research with them is almost impossible. The Home Office, in a money-making exercise, charges over £3000 for a Schedule 1 licence that takes one to two years to get.  It  requires all those working with these drugs to pass a higher CRB check, even if, like me, they are licensed doctors. I can prescribe heroin but need special clearance to prescribe  cannabis for research in case I am tempted to misuse it!  These absurd regulations are so onerous that only 4 hospitals in the UK have a Schedule 1 licence which is why so little therapeutic research on cannabis takes place in this country. This is especially frustrating as UK scientists were the first to identify many of the chemicals found in the cannabis plant. Now we lag years behind Israel and the Netherlands.

DrugScience has repeatedly tried to get the Home Office to be more logical about this state of affairs, in particular over one cannabis derivative: THCV (also known as cannabivarin).  UK scientists from Reading University were the first to show that this has potent anti-epileptic properties. Other UK researchers have shown THCV to have potential in obesity, anxiety and even possibly as a treatment for schizophrenia.  However this research has been very difficult; for example it took Prof. Phil Cowen in Oxford two years to get permission to use THCV in an anxiety experiment in normal volunteers, let alone patients.  The Schedule 1 status also adds massively to the costs of the drug as all the suppliers and manufactures need to get licenses too.

Because of this difficulty a number of psychopharmacology experts including Prof. Robin Murray from the Institute of Psychiatry asked the ACMD to review the status of THCV since their experience suggested that it was not like d9THC – if anything it was an anti-THC behaving rather as an antagonist. So there would be no abuse potential and so no reason to keep it as Class B.

This week the ACMD reported on its review of plant-based cannabinoids and decided that THCV should stay in Schedule 1 despite the body of data I have already mentioned. Their decision on THCV makes embarrassing reading to anyone hoping for a rational policy that would balance scientific goals with public concerns.

I will summarise their decision for you. They found a study that reported in 1974 which found some d9THC-like psychoactivity from THCV. This study was flawed in many respects and would not be accepted by current scientific journals because there was no placebo condition so blinding was impossible.  Moreover in this study the THCV was given intravenously and in high doses, both of which would be predicted to alter its brain effects. Finally there was no proof of quality control so it may have had some d9THC or other psychoactive cannabinoids in it.  These flaws mean its findings are of little relevance to the current human therapeutic situation where the drug would be given orally.  However the ACMD group decided to cling to this straw of possible d9THC-like psychoactivity rather than accept the newer literature that shows it may be a d9THC antagonist. They recommended keeping it a Schedule 1 drug until more research of therapeutic value has been done, which will now probably never happen [at least in the UK] for the reasons described above. 

This is a hugely disappointing decision because if THCV is a functional cannabis antagonist it could be very useful as an antidote for the psychosis-producing effects of the vast range of synthetic cannabinoids (spice) that are ravaging our prisons and poorer communities. The only other cannabis antagonists that might be useful in this current public health emergency such as rimonabant have long since disappeared when their benefits were dismissed by the FDA. 

What should the ACMD have done?  They should have had the courage to acknowledge the therapeutic potential of THCV and moved it completely out of the MDAct1971 just like cannabidiol (CBD).  This would have allowed researchers much faster and cheaper access and also encouraged many more into this research space. This would not have led to increased recreational use as THCV is a) very expensive and b) only psychoactive when injected intravenously, an action few, if any cannabis users would even consider, let alone do. Even if it turned out that THCV did have some recreational use, this could then be dealt with through the new 2016 Psychoactive Substances Act, which, though intellectually dishonest, does at least have the merit of specifically exempting research from penalties.