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P HAWKES
A CALL FOR LEGALISATION OF CANNABIS SATIVA IN SOUTH
AFRICA.
We present a two stage proposal for the legalisation of Cannabis
sativa (marijuana or dagga) in South Africa for consideration by
the
Constitutional Court.
1. Introduction
The recent history
(this century) of Cannabis legislation has been characterised by misinformation
and scare tactics by authorities
world-wide (the US 'Killer Drug' campaign
initiated in the 1930's is a prime example (Grinspoon 1969)). Over the past 3
decades,
a considerable amount of scientific research has been carried out on
this drug, but the arguments between pro- and anti-Cannabis
lobbies have
continued with unabated vehemence. In this proposal we review evidence
concerning possible harmful effects of Cannabis
and compare its effects with
those of the currently legal drugs, alcohol and nicotine, in an attempt to
introduce some rationality
to this debate.
In section two we outline our
proposal whereby legalisation may be achieved with control of quality and
distribution. In section
three we describe briefly the historical precedent of
and reasons for legal use of Cannabis and examine the often illogical reasons
given for banning its use. We provide support for the view that legalisation is
better than either banning or decriminalisation
from the point of view of the
user as well as for fulfilling the aims of support groups such as the South
African National Council
for Alcoholism and drug abuse (SANCA) and the
Department of Welfare. The current world legal status of Cannabis is also
reviewed.
In section four several popular myths and propaganda
surrounding Cannabis and its use are presented together with scientific evidence
contradicting many of these beliefs. In the fifth section we discuss these and
further evidence regarding Cannabis and other drugs
such as alcohol and tobacco
and present our conclusions for consideration by the Constitutional
Court.
2. Proposal
We suggest that legalisation of Cannabis
should be achieved in two stages:
1) Decriminalise its use and the
growing of limited quantities for personal use, while setting up the relevant
control structures
for regulating the future use of Cannabis as a legal
commodity. This would have the desirable effect of immediately alleviating
some
of the pressure on our overpopulated prisons and over-stretched police force,
allowing them to focus on the serious crime problem
currently facing this
country. At this stage, while possession of small amounts for personal use
would be legal, the sale of Cannabis
would remain illegal. This would preclude
having to re-ban unlicensed ("black-market") sales after full
legalisation.
[It has already been pointed out by the Minister for
Correctional Services, Mr Sipho Mzimela, that last year alone over 11000 people
were arrested for Cannabis-related offences, which would cost the State
R198-million if each were sentenced to one year's imprisonment
(The Star, 20
June 1995). Since the Drugs and Drug Trafficking Act 140 of 1992 allows
sentences of up to 15 years for possession
of an undesirable
dependence-producing substance (as Cannabis is defined) this may well be an
underestimate. Such money could surely
be better utilised to combat serious
crime or by the RDP.]
2) A Cannabis control board or authority, similar
to those currently in place for the control of tobacco and alcohol, should then
be set up to-
a) register producers and classify crops with respect to
their use for
i) drug uses (both medical and recreational)
ii) economic
uses (fibre for paper and cloth, seeds for oil and protein).
South African
Cannabis production far exceeds the amount that can be consumed by the local
drug market; an attempt should be made
to encourage producers to grow low
potency varieties for use in fibre, paper pulp and seed production.
b)
control licensing of retailers in a similar manner to that currently used for
alcohol sales. We also suggest that the sale of
both Cannabis and tobacco be
included as part of a single license with that for liquor and that the sale of
all of these drugs be
subject to health warnings and be restricted to persons
over the age of 18.
c) analyse crops for THC (see note 1) and
tar/condensate content (similar to nicotine and tar analysis for tobacco) and
grade them
accordingly. Taxation/excise duties could be imposed on a sliding
scale according to THC content, as is currently done with regard
to alcohol
content of beverages. Inferior or contaminated crops could be rejected and thus
prevented from reaching the market.
3. Historical
perspective
Cannabis has been used throughout the world for thousands
of years (records date at least as far back as 2737 BC (Lemberger 1980))
for
religious/ritualistic, medical, economic and recreational purposes. Until early
this century little or no legislation controlling
its use had ever been
enforced. Then, apparently influenced by a 1913 PhD dissertation entitled "The
smoking of dagga (Indian Hemp)
among the native races in South Africa and the
resultant evils", South Africa joined Egypt in petitioning the League of Nations
to
include Cannabis on the list of habit-forming drugs which was accepted by the
Geneva Convention in 1925 (Neethling 1983). In the
Medical, Dental and Pharmacy
Act 13 of 1928 Cannabis was prohibited. The racial basis of this prohibition
was carried over into
the American campaign which resulted in the banning there
of Cannabis in 1937 (Herer 1993). The legislation dealing with Cannabis
was
modified in 1971 when Connie Mulder introduced the 'Dagga Act' (41 of 1971)
after Defence Force tests alleged that the spread
of its use among young white
males would reduce their abilities to fight the "Total Onslaught' and that
inter-racial social interactions
among youth might be encouraged (Wild 1995).
The Drugs and Drug Trafficking Act 140 of 1992 has since supplanted this
legislation.
3.1 Economic uses
The seeds of Cannabis sativa
contain a very high grade of oil (used for soap-making, as an emulsifying agent
in the leather industry
and in paints) and also have an even higher protein
content than Soya and are used in bird and poultry feed. Cannabis yields one
of
the finest fibrous materials available and may be used in the manufacture of
rope, cloth and paper. Annual yields of paper pulp
are significantly higher per
hectare than from trees. (Herer 1993, Hill 1952, Langer and Hill 1982,
Purseglove 1969, Stanford 1934)
3.2 Medical uses
Cannabis has been
used for medicinal purposes for at least 5000 years. It has been used at
various times to treat asthma, as an anti-convulsant,
antiemetic (e.g. for
reduction of nausea in cancer patients undergoing chemotherapy), as an appetite
stimulant (e.g. in AIDS patients),
in the treatment of glaucoma, as an analgesic
(e.g. by multiple sclerosis and migraine sufferers) and as an anti-inflammatory
agent.
While some controversy surround its use in some of these treatments,
Cannabis or its derivatives have proved very effective in some
cases,
particularly in the treatment of multiple sclerosis and cancer patients and
there are many other potential medicinal uses
(Dewey 1986, Grinspoon 1969,
Lemberger 1980, Martin 1986, Zimmerman et al. 1980).
3.3 Current world
status
Despite the worldwide trend toward banning it in the first half of
this century, Cannabis appears to have remained legal in several
Middle Eastern
countries, in some of which alcohol is banned. There has been a recent reversal
of the earlier trend, and Cannabis
has been legalised to a limited extent
(mostly for economic and medical purposes) or decriminalised (for personal drug
use) in numerous
countries (e.g. Holland, Germany, Poland, Canada, South
Australia and Australian Capital Territory, Britain, Canada, Alaska and some
11
other states in the USA). The main reason for this trend appears to be the
realisation that the dangers of Cannabis use had been
grossly exaggerated during
the anti-drug campaigns earlier this century. The Times (25 June 1 995)
recently reported that the British
Medical Association will argue for
legalisation of all drugs in a report due for publication in the near
future.
At present Cannabis is listed in Part III of Schedule 2
('Undesirable dependence-‑producing substances') of the Drugs and Drug
Trafficking act 140 of 1992. Its placement in this schedule should be reviewed,
as its classification as a dependence-producing
substance is tenuous at best,
and the two currently legal drugs, alcohol and tobacco, which are both far
stronger producers of dependence,
are not listed in any part of this
schedule.
We feel that it is also pertinent at this stage to point out
that sections 20 (Presumptions relating to possession of drugs) and 21
(Presumptions relating to dealing in drugs) (a) (i), (ii) and (iii) of this Act
are unconstitutional in terms of section 25 (3) c)
(to be presumed innocent and
to remain silent during plea proceedings or trial and not to testify during
trial) of the Constitution
of the Republic of South Africa Act No. 200 of 1993.
These sections of the act must be repealed whether or not other changes are
made
regarding the legal status of Cannabis.
3.4 Reasons for retaining the ban
on Cannabis
One of the most common reasons cited against
decriminalisation or legalisation of Cannabis is that 'it will lead to a
dramatic increase
in consumption'. The International Narcotics Control Board
(INCB) appears to support this view (Burgersdorp Nuus, 19 May 1995).
During the
past two decades Cannabis has been decriminalised to varying degrees in a number
of countries and states world-wide (see
section 3.3); in all of those in which
studies have been undertaken there has been either no change or a decrease in
consumption
following decriminalisation (Clark 1987, Quinn 1990, 1991). There
is thus no reason to believe that changes in the legal status
of this drug will
have any significant effect on the levels of its consumption. The persistence
of anti-drug lobbies in citing this
fallacious reason against legalisation in
spite of all indications to the contrary is an indication of their refusal to
objectively
assimilate factual information into their policies.
The
Department of Welfare was recently quoted as stating 'There would be no control
on sale, potency, production, manufacture and
age restriction if dagga is
legalised' as an argument against legalisation (Burgersdorp Nuus, 19/5/1995).
This has to rate as one
of the most profoundly ridiculous statements ever made
in the history of the Cannabis debate. It is obvious that no such control
exists with the current legal status of Cannabis, that control could not be
effected with mere decriminalisation and that the only
way to introduce control
is by legalisation. The possibility that future legislation regarding Cannabis
could lie in the hands of
groups capable of missing the illogicality of such a
statement is frightening indeed.
Another argument often quoted in
response to suggestions that taxation of legalised Cannabis could be a major
source of revenue is
that the State should not be seen to profit from drug taxes
as this would imply support for drug use. Revenue accrued in South Africa
from
the sale of alcohol totalled approximately R2.39 billion in 1994, and from
tobacco sales approximately R1.17 billion (Finance
Department, 1995). Exactly
how this profit from the sale of legal drugs could be construed as different
from that which would be
obtained from the sale of legal Cannabis is unclear, to
say the least.
A further objection (perhaps somewhat in conflict with the
previous one) is that large amounts of tax revenue will be lost due to
users
growing their own Cannabis. This seems unlikely, as it is presently legal to
brew alcoholic beverages, and we are not aware
of any legislation banning
private growing of tobacco; the amount of taxation derived from these drugs does
not appear to suffer
adversely from such untaxed production. If Cannabis were
legally available the vast majority of users would prefer to buy it ready
to use
rather than to wait the several months required to grow it.
It has also
been suggested that legalisation of Cannabis will lead to an increase in the
number of accused persons pleading intoxication
as a defence against criminal
liability. Such a defence has however already been effectively precluded by the
creation of the crime
of 'statutory intoxication' in section 1 of the Criminal
Law Amendment Act 1 of 1988, which applies equally to legal and illegal
intoxicants.
3.5 Prohibition, Decriminalisation or
Legalisation?
Currently held viewpoints in South Africa vary from total
opposition to decriminalisation or legalisation of Cannabis (Department
of
Welfare: Burgersdorp Nuus 19/5/1995, Freedom Front: The Star 20/6/1995), through
support for a very limited decriminalisation
(SANCA: personal communication),
apparent support for a more liberal decriminalisation (Minister for Correctional
Services, Mr Sipho
Mzimela: The Star 20/6/1995), to support for very liberal
decriminalisation or full legalisation (present submission, former Durban
City
Councillor Peter Mansfield: Argus South 30/5/1995).
It is well documented
that world-wide attempts to control the use of drugs by banning their use have
failed, and that the number of
users declines or remains static after controls
are lifted (Quinn 1990, 1991). Given this, and assuming that the aims of
organisations
such as SANCA and the Department of Welfare are to minimise the
harm done by drug users to themselves and to society, we believe
that full
legalisation with suitable control of sale and quality is the only means by
which these aims can be achieved. The majority
(80% in the USA) of deaths
associated with all illegal drugs are caused by their illegality (murders
associated with 'black market',
poisoned drugs etc.) and not by the drugs
themselves (Quinn 1990, 1991). With regard to Cannabis, for which there has
never been
a recorded overdose death, one can only assume that this percentage
would be even higher (virtually 100%). Most of the harm caused
to users of
Cannabis is thus not caused by the drug itself, but by the laws (and the agents
enforcing these laws) that were supposedly
created for their
protection.
While limited decriminalisation of Cannabis as envisaged by
SANCA might be of slight benefit to the user in that the risk of a
career-destroying
criminal record is removed, the user is still forced to commit
a crime by buying or growing the drug.
A more complete decriminalisation,
allowing the cultivation of a small number of plants for personal use (as in
e.g. South Australia
and the Australian Capital Territory, Alaska, Holland and
Portugal), allows the user the option of not committing any crime, not
having to
associate in any way with 'black market' elements and not risking the purchase
of Cannabis contaminated with fungi or pesticides.
We believe that full
legalisation, in conjunction with control over quality and sale as described in
section 2, would far better support
the aims of SANCA and the Department of
Welfare, as well as affording users the full benefit of quality control,
knowledge of the
strength of Cannabis purchased, and complete decoupling of
Cannabis from the illegal drug trade (especially important here is Mandax).
Users worried about excessive use would be far more likely to volunteer for help
(as with alcoholics) if the fear of criminal prosecution
is removed, and even
more so if the stigma of illegality no longer exists.
4. Dispelling
the myths
Following is a table listing common myths, propaganda and
arguments against legalisation expounded by persons and groups concerned
that
Cannabis may pose a danger to society. In each case we present scientific
evidence relating to these beliefs and where applicable
comparisons with alcohol
and/or tobacco. We have not specifically referred to sources for these claims,
but many can be found in,
for example, Moiler (1987), who cites SANCA as his
source of information.
Claims against Cannabis
1. Cannabis is
an addictive drug
Scientific evidence
Cannabis is at worst
considered to produce mild to moderate psychic dependence, with little or no
physical dependence (W.H.O. classification,
Dewey 1986, Grinspoon 1969, Nahas
1981)
Tobacco/alcohol comparisons
Nicotine is regarded as on of the
most physically addictive substances known (see Barecchi et al. 1995, Elders
1994, Quinn 1991),
and marked physical and psychic dependence occurs. Alcohol
is classified by the W.H.O. as producing mild to marked psychic and physical
dependence.
Claims against Cannabis
2. Cannabis usage leads on
to the use of hard drugs
Scientific evidence
“There is no
evidence that marihuana is more likely than alcohol or tobacco or tobacco to
lead to the use of narcotics”
(Grinspoon 1969)
Tobacco/alcohol
comparisons
A higher proportion of heroin users had been users of alcohol
and tobacco than had used marihuana (Grinspoon 1969), which suggest
that in fact
these may be more likely to act as “gateway” drugs. Tobacco use
was found to be the best predictor of alcohol, Cannabis and hard drug usage in
American school children in the 1970’s (Rittenhouse
1981)
Claims against Cannabis
3. Cannabis leads to violent and
aggressive behaviour and criminal activities.
Scientific
evidence
Salzman et al. (1976) showed a significant decrease in hostility
in small groups of people under the influence of Cannabis.
Tobacco/alcohol comparisons
Alcohol is known to increase
aggression.
Claims against Cannabis
4. Cannabis impairs
ability to drive a motor vehicle or to operate machinery.
Scientific
evidence
While Cannabis does cause slight impairment of driving ability,
it does so to a far lesser extent than does alcohol (Grinspoon 1969,
see note
2). We do not in any case advocate driving under the influence of any drug, and
believe that current legislation adequately
covers this.
Tobacco/alcohol
comparisons
Alcohol is implicated as a causative agent in approximately
50 % of all motor vehicle accidents in South Africa (Drive Alive estimate:
implies approximately 5 000 deaths per year) and 40 % (=c.20 000) of MVA
fatalities in the USA.
Claims against Cannabis
5. Cannabis
smoke contains more tar than cigarette smoke so the risk of lung cancer is
greater for Cannabis smokers than for tobacco
smokers.
Scientific
evidence
In view of the huge range of values (1->20mg tar per
cigarette) the exact ratio is impossible to ascertain, but Cannabis smoke
is
commonly assumed to contain twice as much tar as tobacco smoke, with some
estimates (Wu et al. 1988) of as much as 4 times. In
order to take in the same
amount of tar that an average (c.20 cigarettes/day) tobacco smoker would thus
need to smoke about 5-10
“joints” per day. Such high usage is
uncommon, and 5-6 joints per day is considered “heavy” use. Most
user
in the USA average less than 1 joint per day (Wu et al. 1988) and are thus
at worst exposed to dangers comparable to a very light
4 cigarettes/day) tobacco
smoker.
Use of smaller quantities of more potent forms or alternative
methods of administration (smoking through waterpipes or other waterpipes
or
other filtration mechanisms, ingestion by eating or drinking) may be used to
reduce to completely eliminate problems associated
with tar in Cannabis
smoke.
Tobacco/alcohol comparisons
At present 1 in 9 deaths (= at
least 22 00 per year) in South Africa are attributable to smoking related
causes such as cancer and
emphysema (MRC survey 1995). In the USA a similar
proportion (1/7= 390 000) of annual deaths are attributed to tobacco (Quinn
1991).
Alcohol consumption has been correlated with cancer of the upper
alimentary and respiratory tracts as well as cancer of the upper
alimentary and
respiratory tracts as well as cancers of the large bowels, pancreas, stomach and
breast, the latter being evident
with even moderate (1-2 drinks/day) consumption
(Garro and Lieber 1990). A major problem with alcohol is that it seems to act
as
co-carcinogen, enhancing the cancer causing properties of other substances
such as tobacco (Garro and Lieber 1990).
Claims against
Cannabis
6. Long-term use of Cannabis leads to damage to physical and
mental health. Many potential forms of damage are attributed to the
use to
Cannabis, such as weight loss, reduced testosterone levels, infertility and
menstrual disorders, harm to foetus’s and
psychological
disorders.
Scientific evidence
While it is clear that excessive use
of Cannabis may have some adverse side effects, many of the studies suggesting
toxic effects
of cannabinoids are based on the use of extremely high
concentrations (usually 50-100 times the normal human psychoactive dose, but
sometimes as much as 2 000 times) in animals. While Rosenkrantz (1983) has
attempted to justify the use of such doses, we believe
that his argument is
flawed (see note 3.)
It appears that most Cannabis users with personality
disorders or other psychological problems were already suffering from these
before
starting to use the drug, so that in some cases use of Cannabis may have
triggered latent problems (Grinspoon 1969). 2 of four cases
gleaned from 20
years work with adolescent Cannabis users had required treatment before they
started to use the drug (Milman 1981)
Tobacco/alcohol
comparisons
The dangers of long-term usage of both alcohol and tobacco
are well-known. While figures are not available for South Africa, estimates
in
the USA suggest that 80 000 - 100 000 deaths per year in the mid 1980’s
were directly due to alcohol consumption, with another
100 000 in which alcohol
was a contributing factor. As mentioned above, tobacco causes some 390 000
deaths per year in the USA,
while no deaths directly attributable to Cannabis
consumption have ever been recorded.
Claims against Cannabis
7.
The THC content of Cannabis today is 20-30 times as high as it was in the
1960’s and early 1970’s
Scientific evidence
This is not
true. While some slight improvements by breeding and better cultivation methods
may have been achieved, THC contents
have increased only slightly (compare e.g.
Weil et al. 1968 - THC 0.9% = average - with Ghodse 1989 - THC 1-2%). It would
be surprising
indeed if a great increase was obtained in the decade or so in
which it claimed, after at least 5000 years of breeding had failed
to produce
such results. Stronger forms such as hashish and hash oil have been available
throughout recent history. It is also
not clear why higher concentrations
should be considered a problem: users tend to adjust the amount used so that the
same effect
is achieved regardless of the strength. As mentioned in 5 above,
more potent forms should in fact be welcomed because of the reduction
in
exposure to tar.
Tobacco/alcohol comparisons
Alcoholic drinks are
available in a variety of strengths, with a 25 - 30 fold range from the light
beers to the strongest spirits.
Although distilled and fortified wines are
fairly recent additions to the range, we are not aware of this having ever been
suggested
as a reason for banning alcohol. As with Cannabis, users (usually)
adjust their intake according to strength.
Claims against
Cannabis
8. Cannabis has no medical uses.
Scientific
evidence
As discussed earlier, Cannabis and its derivitives may be used
for a wide variety of medical treatment.
Claims against
Cannabis
9. Cannabis uses causes hallucinations
Scientific
evidence
Perceptual distortions may result from very high doses, but
these are better described as illusions, rather than
hallucinations.
Claims against Cannabis
10. THC remains active
in the body for weeks or months after use of Cannabis.
Scientific
evidence
While THC does have a fairly long half-life (a few days) in the
body, it appears to be inactivated, at least in psychoactive terms,
within a few
hours.
Tobacco/alcohol comparisons
Alcohol remains detectable in
the blood for up to 24 or more hours after even light drinking; after heavy
consumptions intoxication
may last well into the day following
intake.
5. Conclusions
A number of reasons have been
put forward in various proposals for the legalisation of Cannabis; some of
these, such as economic uses,
we have considered briefly, others such as the
"freedom of religion" argument of the Rastafarians, to whom Cannabis is a
sacrament,
we feel have been adequately covered in other proposals: we have
concentrated here mainly on the use of Cannabis as a recreational
drug.
While we do not claim that there are no health risks associated
with the use of Cannabis, it seems clear that these are extremely
mild by
comparison with the currently legal alcohol and tobacco. Death rates due to
drug use in the USA show that tobacco is by
far the most dangerous (650 deaths
per 100 000 users per year), alcohol second (150 deaths per 100 000), followed
by heroin (80 deaths
per 100 000) and cocaine (4 deaths per 100 000) (Quinn
1990, 1991). Cannabis is not listed as no deaths directly due to this drug
have
ever been recorded. There is no evidence that use of Cannabis is more likely
than use of alcohol or tobacco to lead on to the
use of "hard" drugs (Grinspoon
1969); in fact tobacco seems to have a much stronger link to such a progression
(Rittenhouse 1981).
It is difficult to believe that the present system has
really been produced in order to protect the public from Cannabis when 1)
we are
told that if we must use drugs we must choose between two of the most dangerous
known and may not use the probably least harmful
and 2) it is obvious that the
original reasons for banning Cannabis were political and racial motivations
rather than health considerations.
We also believe that control of drug
usage by prohibition has proved ineffective, and that the widespread
dissemination of misinformation
by opponents of drug use has probably lead to
increased usage: once a person discovers that much of the available information
about
a given drug is untrue, he or she is more likely to believe that it is
harmless, as well as doubting the validity of warnings about
other drugs. We
feel that while warnings about health hazards should be given for all drugs,
these should be valid warnings, not
scare-mongering falsehoods as has usually
been the case. It is worrying that the main distributors of such misinformation
appear
to be those in whom the most trust is often placed when policy decisions
are to be made. We strongly urge the Constitutional Assembly
to approach
organisations in other countries, where Cannabis has been decriminalised or
legalised or where such changes are being
contemplated, for further information
and advice.
We believe that full legalisation with effective control over
growth, quality and distribution is the best means of minimising health
hazards
associated with Cannabis. We also believe that other benefits, such as added
revenue, reduced expenditure on law enforcement,
decoupling of Cannabis from
other drugs such as Mandrax, would be advantages of this system over partial
decriminalisation.
Although Clark (1987) believes that full legalisation
would entail renegotiation of or withdrawal from the Single Convention of 1961,
we believe that in terms of Articles 23 and 28 of the Convention, controlled
cultivation of Cannabis may in fact not be in conflict.
Certainly cultivation
of Cannabis for economic purposes (fibre, seed, oil etc.) is specifically
excluded from the scope of the Convention
in Article 28. Clearly interpretation
of the Single Convention and INCB policies would need thorough investigation if
full legalisation
is contemplated.
P.G. Hawkes
A.D Brink
30
June 1995
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7. Notes
1. A-9 tetrahydrocannabinol (A-9 THC,
referred to in this submission simply as THC) is the main active constituent of
Cannabis, although
a large number of related compounds are also present in
varying concentrations (Ghodse 1989).
2. Although we do not advocate
driving or operating machinery under the influence of drugs, it is interesting
to note that one of
the precautions listed for patients receiving
tetrahydrocannabinol was that they "should not drive, operate machinery, or
engage
in any hazardous activity until they are able to tolerate the drug and to
perform these tasks safely" (Drug Evaluation Monographs,
Micromedex Inc. 84 Exp.
30/O6/95). In view of the fact that the THC doses prescribed are within the
normal range for recreational Cannabis use, this could be taken
as an indication
that experienced users should be able to perform such operations safely while
intoxicated.
3. Rosenkrantz (1983) notes that proponents of Cannabis use
often criticise the "excessive doses" administered to animals and states
that
"Few ears and minds are receptive to the concept that large doses must be used
in order to evoke toxic signs deliberately".
This statement implies that such
studies have been carried out with the express intention of producing toxic
effects, and that were
these not achieved with the doses used, higher and higher
doses would have been tested until such effects were observed. In terms
of
accepted scientific methodology, this approach is invalid. That a sufficiently
high dose of virtually any substance (water ingested
at a rate of 20 litres/day,
approximately 10 times the normal daily requirement, will result in death due to
kidney failure in a
matter of weeks; this has to our knowledge never been used
as evidence of the toxicity of water, nor as a reason for banning the
consumption of water) will result in adverse effects does not seem to influence
his contention that the results of the study are
applicable to normal human
usage.
This is not the only flaw in Rosenkrantz's argument: he calculates
the dose equivalents for various animals on the basis of a conversion
factor
calculated in some manner (undisclosed in his 1983 paper) from relative body
surface areas, with an estimate of human consumption
as a baseline. We feel
that not only does he overestimate normal human consumption, but that the use of
the body surface area conversion
factor is invalid in the toxicity
studies:
i) An average Cannabis cigarette is generally considered to
contain 0.3-0.5g plant matter at 1-2% THC (Ghodse 1989, Weil et al. 1968),
giving 3-10mg THC per cigarette. It has often been assumed (e.g. Rosenkrantz
1983) that 50% of this THC is lost during smoking,
but 80-85% loss is probably
more realistic (Martin 1986). If a loss of 80% is assumed a cigarette
containing 0.5g of Cannabis with
a THC content of 2% will result in an intake of
2mg THC. In a 50 kg person this yields a dosage of 40gg/kg (0.04mg/kg), which
is
within the range estimated as being sufficient to produce a psychological
"high" (Martin 1986).
Rosenkrantz (1983) assumes a 1g "cigarette"
containing either marijuana (1% THC) or hashish (5% THC), with 50% loss of THC
during
smoking, giving respective THC doses of 5 and 25mg per 50kg person, or
0.1 and 0.5mg/kg. He then calculates doses for light (1 cigarette/day
= 0.
1-0.5mg/kg), moderate (3 cigarettes/day = 0.3‑1.5mg/kg) and heavy (6
cigarettes/day = 0.6-3.0mg/kg) usage. The fact that
his estimate of dosage for
"light" hashish smoking is 83% of the value for "heavy" and 166% of the value
for "moderate" marijuana
smoking does not seem to be of any concern. In general
users will smoke significantly less of a more potent form of marijuana such
as
hashish; to assume equal consumption by weight in this way to be within the same
category of usage is incorrect (Rosenkrantz states
in the same article that " a
general consensus" has emerged that 1,3 or 6 marijuana (not hashish) cigarettes
per day is considered
as light, moderate or heavy use respectively; he neglects
to mention that a large proportion, probably a majority of Cannabis users,
average far less that 1 cigarette per day and that an alcohol user who became
intoxicated on average once a day would be considered
an alcoholic). Although
the total THC content (10mg) of Rosenkrantz's marijuana cigarette is the same as
the upper limit suggested
by Ghodse (1989), his estimate of dosage achieved is
more than double that calculated above, and his estimate for "light" hashish
smoking is 12.5 times the value obtained following Martin's reasoning (1986).
It thus seems clear that Rosenkrantz's baseline estimates
from which the animal
dosages were calculated were too high by a factor of 2-12.5. This view is
supported by the fact that the doses
estimated by Rosenkrantz for dogs and
monkeys respectively are 1-5 and 6-30 times higher than the intravenous doses
needed to produce
profound behavioural changes in these animals (Martin
1986).
ii) Rosenkrantz does not adequately explain why body surface area
should be used to produce conversion factors for calculation of
"equivalent"
doses in animals; he simply states that it has "aided in interpretation of human
and animal responses to Cannabis products"
and does not mention its use in
studies of other drugs. He defends the use of such doses on the basis that
blood plasma levels of
the THC are similar in humans and animals given
,,equivalent" doses. He appears to have failed to realise the implication that
if
plasma levels are equivalent in a mouse given 5mg/kg (a commonly used dose)
and in a human given 0.05mg/kg (a psychoactively effective
dose), absorption
into the mouse tissues must have been more complete and tissue concentrations of
THC in the mouse must be >100
times those in the human. Since cytotoxic
effects occur in the tissues rather than in the blood plasma, this would imply
that mice
might be more, rather than less, susceptible than higher mammals such
as monkeys and man to toxicity of THC. This is supported by
the fact that the
LD50 for THC in mice is significantly lower than for a monkey (40-60mg/kg
compared to 128mg/kg). This means that
"equivalent " doses in a mouse and a
monkey (calculated on the basis of body surface areas) will be approximately 10%
and 1.2% of
the acute LD50's respectively. While the LD,, for THC in man is
unknown, it is likely that it is even higher than that for monkeys.
A
psychoactively effective dose in a human, assuming an LD50 no higher than that
for a monkey, would be 0.04% of the LD50, so that
a commonly used dose in mouse
differs from an effective dose in man relative to the respective LD50's by a
factor of at least 250
(and probably much more). It seems ridiculous to suggest
that toxic effects observed at these doses in mice can be comparable to
those
resulting from normal usage in man. In addition, while doses of roughly 10% of
the LD50 are commonly reported for rats and
mice, in several studies on these
species doses have been used that exceed reported LD50, values (Bhargva 1980:
5‑100mg/kg
in mice, Cutler & Mackintosh 1984: 50-100mg/kg in mice,
Maitre et al. 1970: 10-100mg/kg in rats); in these studies it is surprising
that
most of the animals tested did not die at the higher doses, and it is most
definitely not surprising when effects such as hypothermia
are reported. It
should also be noted that dosage calculation by the body surface are method
would be impossible with a drug such
as alcohol; the "equivalent" of a dose
producing moderate intoxication in a human would be immediately fatal to a mouse
or rat.
Furthermore, while the "equivalent" dose for a mouse is four times that
for a monkey, doses used in chronic studies appear mostly
to be about 2 -5mg/kg
irrespective of the animals used (see e.g. Paton 1975).
It would appear
that the "equivalent" dose calculations presented by Rosenkrantz (1983) are no
more than an attempt to hide the fact
that the results of behavioural and
toxicological experiments in animals are meaningless when compared to
recreational use in man.
The lack of any mention of such calculations in a
discussion of doses in animals as compared to man in a 1986 review by Dewey,
even
though he cites Rosenkrantz (1983), seems to support our view that this
argument was constructed post hoc because criticism of these
dosages had been
voiced. A final criticism of the manner in which high THC doses are
administered is that they are usually given
in a single dose each day in chronic
studies; a heavy human user will take in several smaller doses over a 12-18 hour
period each
day, allowing some of the THC to be inactivated before more is taken
in. Peak levels of active THC will thus be relatively much
higher in the
studies reported than in human users.
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