clinical trials include smoking?
5.54 Both Dr Guy and
the Asscher group have ruled out smoking for the purposes of their
trials; and many of our witnesses would support them (e.g. Notcutt
p 104, Henry p 224, RPharmSoc p 284, Wall Q 103,
Pertwee QQ 266, 315, MSSoc Q 364, ACT Q 154). Smoking
is felt to carry too great a potential health risk: see Chapter 4.
However, as noted above, there are anecdotal reports that those
who use cannabis for medical purposes favour smoked cannabis over
orally administered cannabinoids such as nabilone. The perceived
advantages of smoked cannabis may be due to the rapid absorption
and flexibility of dosecontrol offered by smoking as a route
of administration: see Chapter 3.
5.55 Dr Robson suggested
that there should be a comparison in clinical trials between smoked
cannabis and smoked THC (Q 480). The Asscher group's proposal,
to compare orally administered THC with an orally administered
cannabis product, will achieve the same result, namely a comparison
of like with like.
5.56 There is considerable
discussion of possible improvements in the mode of administration
of cannabis and synthetic cannabinoids (e.g. QQ 60, 266-273).
IDMU (p 235) described recent research in the United States on
the ability of various methods of smoking herbal cannabis to reduce
tar intake relative to THC. Surprisingly, the use of a water pipe,
in which the cannabis smoke is passed through water prior to being
inhaled, and the use of a vaporiser, in which herbal cannabis
is heated but not burned, had relatively little effect in reducing
the amount of tar inhaled. Unfortunately the slow and unreliable
absorption of herbal cannabis and synthetic cannabinoids taken
by mouth can lead to both under and overdosing. Other
possibilities include the development of inhalers (e.g. Guy QQ 713-4),
sprays, rectal suppositories (see Appendix 3, paragraph 3) and
skin patches, and a sub-lingual method (taking a tincture under
the tongueLMMSG p 270). Research on such alternative
delivery systems is held to be a high priority by many witnesses.
5.57 Although there
is general agreement that smoked cannabis carries a potential
risk for long-term users, the medical application of smoked cannabis
is not ruled out by all. The US National Institutes of Health
report says, " ...there might be some patient populations,
e.g. cancer patients experiencing nausea and vomiting during chemotherapy,
for whom the inhalation route might offer advantages over the
currently available capsule formulation [of THC]". They conclude,
"In summary, the testing of smoked marijuana to evaluate
its therapeutic effects is a difficult, but not impossible, task".
The American Medical Association report recommends "that
adequate and well controlled studies of smoked marijuana be conducted
in patients who have serious conditions for which preclinical,
anecdotal or controlled evidence suggests possible efficacy including
AIDS wasting syndrome, severe acute or delayed emesis induced
by chemotherapy, multiple sclerosis, spinal cord injury, dystonia
[involuntary muscle movements, e.g. a tic], and neuropathic pain...".
Among our witnesses, those who would include smoking in trials
include Dr Schon (p 304), Dr Stewart (p 305)
and Dr Robson (Q 480); and Professor Radda of the
MRC would be prepared to do so, provided that the trial protocols
were satisfactory (QQ 646, 654).