Campbell et al's systematic review (1) of the best available evidence
for cannabinoids used as analgesics, and the wide publicity this
generated, illustrate the complex and unique nature of the medicinal
cannabis debate. Complex because of the variability of results obtained
from studying pain of differing pathophysiologies and from employing
various types of cannabinoid. Unique because of its high profile status,
which means that emphasis on a particular aspect can be misinterpreted and
generate myths.
The review has contributed to the impression that cannabinoids are
unlikely to replace the existing effective treatments for post-operative
pain. It has also acknowledged that there are therapeutic areas which are
more intruiging than nociceptive pain, such as neuropathic pain and
spasticity. Indeed, this potential has been illustrated by the one study
reviewed which looked at a single patient with these symptoms, and
demonstrated a beneficial effect on both from delta-9-tetrahydrocannabinol
5mg orally which was well tolerated (2). These contrasting aspects are
contained within the body of the review, yet in the conclusions much more
generalised statements about the potential role of cannabinoids in pain
management are made. The authors also seem to use the terms "cannabinoid"
and "cannabis" interchangeably in the paper, when in fact none of the
reviewed studies used whole cannabis.
The reports of Campbell et al's paper which subsequently appeared in
the lay media further exaggerated these conclusions. Such bias may
undermine the efforts of groups like our own to carry out clinical
research into therapeutic applications for cannabis derivatives which
could have genuine merit.
Medical scientists have an obligation to evaluate reports from the
many patients who find relief from intractable symptoms by using cannabis
illegally. Adequately powered randomised controlled trials are the only
reliable way of achieving this. Fortunately, these are now underway.
1. Campbell FA, Tramer MR, Carroll D, Reynolds DJM, Moore RA, McQuay
H. Are cannabinoids an effective and safe treatment option in the
management of pain? A qualitative systematic review. BMJ 2001; 323:13-16
2. Maurer M, Henn V, Dittrich A, Hoffmann A. Delta-9-
tetrahydrocannabinol shows antispastic and analgesic effects in a single
case double-blind trial. Eur Arch Psychiatry Clin Neurosci 1990; 240(1):1-
4
Petra Makela
Research Registrar
Rivermead Rehabilitation Centre, Oxford
Derick Wade
Consultant and Professor in Neurological Disability
Rivermead Rehabilitation Centre, Oxford
Philip Robson
Senior Research Fellow
University Department of Psychiatry,
Warneford Hospital,
Oxford
Possible competing interests:
We are currently conducting clinical research into the use of
cannabis extracts supplied by GW Pharmaceuticals plc for the treatment of
pain, spasticity and other symptoms in neurological conditions. Dr Robson
also holds the post of Medical Director for GW Pharmaceuticals.
Rapid Response:
Therapeutic Potential of Cannabinoids
Campbell et al's systematic review (1) of the best available evidence
for cannabinoids used as analgesics, and the wide publicity this
generated, illustrate the complex and unique nature of the medicinal
cannabis debate. Complex because of the variability of results obtained
from studying pain of differing pathophysiologies and from employing
various types of cannabinoid. Unique because of its high profile status,
which means that emphasis on a particular aspect can be misinterpreted and
generate myths.
The review has contributed to the impression that cannabinoids are
unlikely to replace the existing effective treatments for post-operative
pain. It has also acknowledged that there are therapeutic areas which are
more intruiging than nociceptive pain, such as neuropathic pain and
spasticity. Indeed, this potential has been illustrated by the one study
reviewed which looked at a single patient with these symptoms, and
demonstrated a beneficial effect on both from delta-9-tetrahydrocannabinol
5mg orally which was well tolerated (2). These contrasting aspects are
contained within the body of the review, yet in the conclusions much more
generalised statements about the potential role of cannabinoids in pain
management are made. The authors also seem to use the terms "cannabinoid"
and "cannabis" interchangeably in the paper, when in fact none of the
reviewed studies used whole cannabis.
The reports of Campbell et al's paper which subsequently appeared in
the lay media further exaggerated these conclusions. Such bias may
undermine the efforts of groups like our own to carry out clinical
research into therapeutic applications for cannabis derivatives which
could have genuine merit.
Medical scientists have an obligation to evaluate reports from the
many patients who find relief from intractable symptoms by using cannabis
illegally. Adequately powered randomised controlled trials are the only
reliable way of achieving this. Fortunately, these are now underway.
1. Campbell FA, Tramer MR, Carroll D, Reynolds DJM, Moore RA, McQuay
H. Are cannabinoids an effective and safe treatment option in the
management of pain? A qualitative systematic review. BMJ 2001; 323:13-16
2. Maurer M, Henn V, Dittrich A, Hoffmann A. Delta-9-
tetrahydrocannabinol shows antispastic and analgesic effects in a single
case double-blind trial. Eur Arch Psychiatry Clin Neurosci 1990; 240(1):1-
4
Petra Makela
Research Registrar
Rivermead Rehabilitation Centre, Oxford
Derick Wade
Consultant and Professor in Neurological Disability
Rivermead Rehabilitation Centre, Oxford
Philip Robson
Senior Research Fellow
University Department of Psychiatry,
Warneford Hospital,
Oxford
Possible competing interests:
We are currently conducting clinical research into the use of
cannabis extracts supplied by GW Pharmaceuticals plc for the treatment of
pain, spasticity and other symptoms in neurological conditions. Dr Robson
also holds the post of Medical Director for GW Pharmaceuticals.
Competing interests: No competing interests