Subj: No cut-and-dried conclusions in the great cannabis debate

Date: Feb 19, 1998

Source: The Scotsman

Author: Dr Roger Pertwee. Dr Pertwee is a reader in biomedical sciences,
Aberdeen University, and President of the International
Cannabinoid Research Society.

No cut-and-dried conclusions in the great cannabis debate

The plant known as Cannabis sativa has been used in various
forms as a painkiller for at least 5,000 years. But it has
only recently been recognised by the scientific community as
the source of a set of more than 60 related chemicals called
cannabinoids.

In November the British Medical Association issued a report,
of which I was a contributing author, calling for more
clinical studies of cannabinoids as medicines. It was a
welcome sign that the establishment was beginning to take the
issue seriously.

The BMA is not advocating smoking dope, which is carcinogenic
because of the tars produced when it is lit, but there are
nevertheless strong arguments for allowing some of its
constituent chemicals to be used in medical treatment.

The best known of these chemicals is delta-9-
tetrahydrocannabinol (THC), to which most of the known
pharmacological properties of cannabis, including its effects
on mood and perception, can be attributed.

For many years its precise mode of action remained a mystery,
but all this changed recently with two discoveries: first,
that our body contain specialised sites (cannabinoid
receptors) that mandate many of the effects of THC, and,
second, that our tissues can produce their own cannabinoids
that interact with these receptors to control the release of
chemical messengers in the body.

Two cannabinoids - THC, also known as dronabinol, and
nabilone - are already used clinically in this country and
elsewhere to suppress nausea and vomiting provoked by cancer
chemotherapy. in the United States, doctors can alco
prescribe THC to boost the appetite of AIDS patients and so
reduce loss of body weight.

It is likely that cannabis and individual cannabinoids would
also be effective in relieving the muscle spasms, pain and
bladder dysfunction of multiple sclerosis and spinal injury,
in managing other types of pain and in treating glaucoma and
bronchial asthma.

A few British doctors prescribe nabilone for multiple
sclerosis or chronic pain, despite the fact that it is not
licensed for these purposes.

The evidence supporting such use, based on anecdotal,
pharmacological and clinical data, is particularly promising.
Seven trials, albeit with rather small numbers of patients,
have shown that cannabis, THC or nabilone can reduce the
intensity of at least some symptoms, particularly muscle
spasm, pain and bladder dysfunction.

THC has also been shown to be effective in an animal version
of MS. Results from other trials, as well as from animal
studies, lend further support to the claim that THC relieves
pain.

Meanwhile, a survey that I conducted with colleagues recently
found that among 112 MS pateints who use cannabis - illegally
under current laws - almost all listed multiple benefits.
Improvements included a reduction in muscle spasms when
falling asleep (96.5 per cent), decreased spasms when waking
at night (93.2 per cent), relief from pain in the legs at
night (92.3 per cent), from arm or head tremors (90.7 per
cent) and from depression (90.6 per cent).

While many find such data convincing, others would like to
see larger, more extensive clinical trials.

It is this approach that the BMA recommended in the recently
published report 'Therapeutic uses of Cannabis', concluding
that patient groups, pharmaceutical companies and the
Department of Health should jointly encourage properly
conducted clinical trials to evaluate the further potential
therapeutic uses of cannabis - alone or in combination with
other drugs. We at Aberdeen intend to carry out such a trial
if we can obtain funding.

Meanwhile it must be remembered that some of the effects of
cannabis and THC are potentially hazardous. Among the
possible problems are increased heart rate and altered
hormone release, and evidence that cannabis can induce
psychosis in individuals predisposed to schizophrenia.

But although cannabis is carcinogenic when smoked, it is
effective by other routes, and data strongly suggest it is
not strongly addictive. There is no pharmacological evidence
that cannabis use leads to the taking of other illegal drugs.

Evidence that cannabis and cannabinoids can produce adverse
effects should not rule out their use as medicines, as these
effects are no worse than those of some prescribed drugs.

It can now be prescribed in Italy as well as in Arizona and
California (according to state laws). It could also be
prescribed in this country until 1971, and in 1968 a
government advisory committee concluded in its report to the
Home Office (the Wootton report): "Preparations of cannabis
and its derivatives should continue to be available on
prescription for purposes of medical treatment and research".

There is no doubt that further research into the medicinal
properties of cannabis and cannabinoids is needed. We also
need to develop better ways of administering it, possibly as
suppositories.

As all this will take considerable time, a strong case can be
made for allowing doctors to prescribe cannabis, nabilone or
dronabinol for disorders such as MS and spinal injury. This
would seem preferable to the present state of affairs where
many patients who in all other ways appear to be law-abiding
citizens feel so strongly that they need the medical benefits
of cannabis that they are prepared to risk punishment.

They have no medical supervision and no knowledge of its
potency and pedigree, which could mean inadvertently taking
in pathogenic organisms, microbial toxins, other drugs or
even pesticides.