CANNABIS THERAPY 'MAY BE HARMFUL'

Cannabis extracts used in medicines may worsen symptoms rather
than have the beneficial effects that are intended, it has been reported.

Cannabis extracts can be harmful because of the unpredictable way the
body reacts, New Scientist said.

Research detailed to the Federation of European Neuroscience Societies
found boosting levels of some cannabinoids worsened epilepsy and
Alzheimer's.

Experts said it was hard to target the drug at specific parts of the
body.

Some compounds in cannabis interfere with a natural signalling system
in the brain, nerves and immune system.

The signalling system, which produces its own cannabinoids, plays a
role in conditions such as MS, epilepsy, Alzheimer's disease,
schizophrenia and Parkinson's disease.

Extra cannabinoids, from smoking cannabis or from medications, can
therefore have a significant effect, researchers suggest.

Vincenzo Di Marzo, of Italy's National Research Council, told the
conference that he had found boosting the level of one natural
cannabinoid, andandamide, in rats initially appeared to protect the
animals from memory loss and nerve degeneration.

But if the rise was prolonged, the cannabinoid could be ineffective,
or even damaging.

Beat Lutz, of the University of Mainz in Germany, found a another
paradox in models of epilepsy in mice.

The same cannabinoid is normally produced by the body during an
epileptic seizure to produce a calming effect.

But he found boosting levels could actually worsen
seizures.

Reason

He said he believed the reason for the findings was that there were
cannabis receptors on two different types of neuron populations which
the drug could affect.

In one group, exposure to cannabinoids increases activity while in the
other, it inhibits it.

Dr Lutz said this meant that depending on which one they hit, the
effect was different.

Professor David Baker, from University College London, who has studied
the impact of cannabis extracts in treating multiple sclerosis, said:
"The problem with cannabis is that there's no way of targeting the
drug to any particular place."

He said the hope was that scientists could manipulate the nervous
system by managing the way cannabis compounds are released just as the
depression drug Prozac does for serotonin by delaying release.

The only cannabis-based drug which can be used in the UK is a
treatment for MS called Sativex.

It has been granted a special licence meaning it can only be used if
the doctor takes responsibility for prescribing it.

The drug, produced by GW Pharmaceuticals, is a mouth spray containing
two chemicals found in cannabis, THC and cannabidiol.

However, it is made using plant cannabinoids, rather than those found
in the body.