THE MEDICINES CONTROL AGENCY AND
THE TOXICITY OF CANNABIDIOL
19. While we are encouraged at the recent change
of attitude shown by the Home Office, we consider that decisions
taken by the Medicines Control Agency (MCA) appear to be inconsistent.
We did not feel that the MCA adequately answered our questions
about the proposed use of cannabidiol in cannabis-based medicines.
We were also disappointed that the witness from the MCA seemed
unprepared even to consider discussing the basis on which the
MCA's decisions were made.
20. Raw cannabis (cannabis sativa) contains
more than 60 cannabinoids and more than 400 chemical compounds.
The two most abundant cannabinoids, which are currently subject
to the most detailed investigation, are delta-9-tetrahydrocannabinol
(THC) and cannabidiol (CBD). Both these cannabinoids are present
in raw cannabis. They are also both present in the cannabis oil
capsules ("Cannador") which Dr Zajicek is proposing
to use in his CAMS trial,
and in the cannabis extracts used by G. W. Pharmaceuticals.
21. THC has long been established in the pharmacopoeia.
The MCA are satisfied that there is adequate information on the
toxicological profile of THC to justify long-term exposure to
THC in the CAMS trial (p. 31). An oral preparation of synthetic
THC in sesame oil ("Marinol") can already be prescribed
22. By contrast, the MCA are unhappy with the toxicology
data on CBD. They said that there is some evidence that CBD inhibits
spermatogenesis in animals, and that overall there is a lack of
adequate data. The MCA have therefore not permitted Dr Zajicek
to proceed with his trial of Cannador (cannabis oil) capsules
beyond 15 weeks. Moreover, the MCA's decision to insist on further
toxicology data on CBD could delay the production of a cannabis-based
medicine by G. W. Pharmaceuticals by as much as 2 to 3 years.
Were the MCA not to require further extensive toxicological studies
on CBD, G. W. Pharmaceuticals claim that they could have a cannabis-based
prescription medicine available for patients in 2003.
23. We note that, according to G. W. Pharmaceuticals,
the Canadian regulatory authorities have stated that they do not
require additional animal toxicology studies for CBD. We put this
to the MCA, who refused to comment (Q. 5); we found this
refusal highly unsatisfactory.
24. We consider that the decision of the MCA is flawed
for three reasons which are discussed in turn below:
(a) the MCA persist in treating
CBD and cannabis oil as "new medicines",
though cannabis oil, which contains both CBD and THC, has a long
history of human use and appeared in the British Pharmacopoeia
Codex until 1948;
(b) the studies which the MCA took to indicate an
inhibition of spermatogenesis involved doses of CBD at least 100
times higher than the doses contemplated by either Dr Zajicek
or G. W. Pharmaceuticals; and
(c) the potential side-effects of CBD about which
the MCA are concerned might be regarded as trivial by those patients,
such as those suffering from multiple sclerosis, who stand to
benefit from medicines incorporating CBD. These concerns could
be dealt with by issuing a warning to physicians who prescribe
cannabis-based medicines. The attitude of the MCA in not allowing
patients to make their own decisions could be regarded as overprotective.
25. Both the MCA and the Home Office persist in treating
cannabis-based medicines as new medicines. Cannabis, however,
has a history of medical use in man stretching back hundreds of
years. For much of the nineteenth century and the first half of
the twentieth century, moreover, it was administered in Britain
as a tincture (cannabis oil in alcohol): thus the oral administration
of cannabis extracts which contain significant quantities of CBD
has a long history of medicinal use. In choosing to ignore the
long history of safe therapeutic cannabis use, and in classifying
cannabis extract (and CBD) as a "new medicine", the
Government and the MCA are treating a long-established herbal
extract as if it were just another new synthetic chemical, and
are thus not making an informed scientific judgement.
26. Campaigners against cannabis have long argued
that it may have adverse effects on human fertility. Despite 30
years of trials, however, this has never been adequately proven.
The trial to which the MCA refer in their oral evidence (Q. 2)
was based on tests in small numbers of animals, and the results
were equivocal, even though the administered doses of CBD were
100-1000 times higher than those proposed for any human medicine.
In short, we regard the raising of this unsubstantiated issue
as further evidence that the MCA have not adopted a positive approach
towards the licensing of a cannabis-based medicine.
27. We are concerned that the MCA's approach to the
licensing of cannabis-based medicines, and their insistence on
the provision of new toxicological data which could delay the
approval of such medicines, place the requirements of safety and
the needs of patients in an unacceptable balance. Patients with
severe conditions such as multiple sclerosis are being denied
the right to make informed choices about their medication. There
is always some risk in taking any medication; patients and their
doctors should certainly be informed about the toxicological concerns
that the MCA have raised, but these concerns should not prevent
them from having access to what promises to be the only effective
medication available to them.
28. Overall, we consider that the MCA's attitude
means that cannabis-based medicines are not being dealt with in
the same impartial manner as other medicines.
29. We believe that a thorough and impartial reappraisal
of the published scientific literature on the safety of CBD and
cannabis extracts should lead the MCA to reconsider their present
overly cautious stance. We are at least encouraged that the MCA
state that they are conducting a more detailed review of existing
literature reports on cannabis and CBD.