Be honest. We all have one. What’s your poison? Booze, tobacco, prescription drugs… or something a little more exotic? Cannabis is a controversial plant, regarded by many as a godsend. If Carlsberg made a ‘erb…
But in all seriousness… How much do we know about cannabis? And are the chemical compounds it contains poison or… panacea?
Beginnings of Toxicology
Until the 19th century, most poisons were undetectable, as well as very common. This state of affairs meant that poisoners could easily escape detection and punishment. As a result, poisoning was widespread in places throughout history, such as in Italy and France in the late 1600s.
In 1813, Mateu Orfila compiled his ‘Traité des Poisons‘ – the book divided poisons into several groups and described their effects on the living body, the symptoms of illness they produce, the signs they leave in a dead body, and the ways of identifying them. It was the beginning of Modern Toxicology.
Many potentially harmful substances are deliberately consumed everyday by average individuals for their mood and mind altering effects. These particular substances are known in legal terms as drugs of abuse. There is an extensive array of them, either produced illegally or diverted from licit sources.
Drugs of Abuse
Depending on how they affect the central nervous system (CNS), drugs of abuse may be categorised into:
Amphetamines and cocaine stimulate the brain activity.
Alcohol, barbiturates, benzodiazepines, heroin inhibit the brain activity.
Ecstasy and lysergic acid diethylamide (LSD) induce alterations in perception and mood.
Drugs are often derived from organically-produced plant chemical compounds.
Plants are brilliant at organic chemistry.
In some countries and U.S. states, cannabis is legal to possess. These include Portugal, the Netherlands, North Korea, Colorado, Washington, Alaska, and Oregon.
One of those ‘drugs of abuse’ comes from a plant, and has become World-renowned for having the most remarkable positive health benefits – cannabis (or marijuana).
Cannabis goes by many names, including
Marijuana is one the names given to the dried buds and leaves of varieties of the Cannabis sativa plant. Cannabis is a genus of flowering plants that includes a single species, Cannabis sativa, sometimes divided into two additional species, Cannabis indica and Cannabis ruderalis. The three taxa are indigenous to Central Asia, and South Asia.
The plants can grow wild in warm and tropical climates throughout the World, and they can be cultivated commercially.
Possibly the most versatile plant on the planet, Cannabis is also possibly the most controversial.
Cannabis is NOT just a great material for making super-capacitors. Its uses range from a popular recreational drug to a potential medicine for a range of currently incurable conditions.
Cannabis is a mild hallucinogen.
A Party Drug
Cannabis is a popular recreational drug around the World, only behind alcohol, caffeine and tobacco. Cannabis is a mild hallucinogenic drug.
In the United States alone, it is believed that over 100 million Americans have tried cannabis, with up to 25 million Americans using it in the past year, and over 14 million doing so regularly despite harsh laws against its use.
In the United Kingdom, Cannabis remains the most popular illegal drug.
According to NHS’s Cannabis Facts, the proportion of 11-15 year olds in England who had used cannabis in the last year fell from 13.3% in 2003 to 7% in 2013. The proportion of 16-59 year old using cannabis in the last year has fallen from 10.6% in 2003-04 to 6.6% in 2013-14.
The psychoactive effects of cannabis are known to have a biphasic nature:
- Primary psychoactive effects include a state of relaxation, and to a lesser degree, euphoria from its main psychoactive compound, THC,
- Secondary psychoactive effects, such as a facility for philosophical thinking, introspection and metacognition have been reported.
A tertiary psychoactive effects of the drug cannabis, can include an increase in heart rate and increased appetite, believed to be caused by 11-OH-THC, the main psychoactive metabolite of THC produced in the liver.
The effects of smoking Cannabis usually begin within 10-20 minutes after absorption, and they may last between two-three hours. To the novice user in particular, they include a feeling of relaxation, sleepiness and a lack of concentration.
Seasoned users report enhanced perception and heightened creativity.
‘Normal’ cognition is resumed after approximately three hours for larger doses via a smoking pipe, bong or vaporiser. However, if a large amount is taken orally, the effects may last much longer. After 24 hours to a few days, minuscule psychoactive effects may be felt, depending on the dosage, the frequency and the user’s tolerance to the drug.
As reported on the Urban75.com webpage on Cannabis:
Side effects: For many, smoking dope is as natural and everyday as a brew of hot tea, and they find the drug helps make their life a little less stressful without unduly affecting their judgement or abilities.
For others it can have quite the opposite effect, turning ordinary folk into unbearable, spaced out, lazy hippies. A night of industrial strength spliffing can transform you into a giggling oaf who will burst into laughter at wholly unamusing incidents and find deep intellectual depth in the Spice Girls’ lyrics.
Your trousers and sofa will become riddled with burn marks from dropped spliffs, and you will have to face the regular dilemma of being hit with the munchies at 3 am only to find that you were too out of it to get the shopping in.
This can result in regular users turning into lazy gits whose crap diet turns their body into a most unattractive proposition.
The common side-effects of Cannabis can include
- dry mouth,
- blurred vision,
- mental confusion,
- spatio-temporal disconnection,
- seizures and
- memory holes.
Cannabis withdrawal symptoms are typically mild and never life-threatening, despite the increasing trend in THC potency of the drug observed in seized marijuana samples over the years.
For this reason, to many users, if Carlsberg made a weed, this would be the one…
For many, smoking dope is as natural and everyday as a brew of hot tea.
And when you look closer at our complex human physiological systems, it appears to make very good sense.
The Endocannabinoid System and Associated Receptors
The Endo-Cannabinoid System is a group of endogenous cannabinoid receptors located in the mammalian brain and throughout the central and peripheral nervous systems, consisting of neuromodulatory lipids and their receptors. Known as “the body’s own cannabinoid system”, the ECS is involved in a variety of physiological processes including appetite, pain sensation, mood, and memory, and in mediating the psychoactive effects of cannabis.
Two primary endocannabinoid receptors have been identified:
- CB1 receptor, first cloned in 1990
- CB2 receptor, cloned in 1993.
CB1 receptors are located primarily in the brain, but they also are found in blood vessels and heart cells. CB2 receptors are primarily located outside of the brain, in the peripheral nervous system and glands.
Since these receptors are so widespread throughout the brain and body, marijuana smoking can have a widespread effect on the brain, heart, cardiovascular system, nervous system, reproductive system, and immune system.
Cannabinoids and the Human Body
The CB1 cannabinoid receptors type 1, are found predominantly in the brain and nervous system, as well as in peripheral organs and tissues, and are the main molecular target of the endocannabinoid ligand (binding molecule), Anandamide, as well as its mimetic phytocannabinoid, THC.
CB1 receptors are metabotropic receptors expressed most abundantly in the brain and their distribution has been widely characterised in humans. CB1 receptors are highly expressed in the
- basal ganglia,
- cortex and
They are less expressed in the amygdala, hypothalamus, nucleus accumbens, thalamus, periapeduncular grey matter and the spinal cord, as well as in other brain areas, mainly in the telencephalon and diencephalum.
CB1 receptors are also expressed in several peripheral organs. Thus, they are present in the:
- smooth muscles,
- gastrointestinal tract,
- pancreatic b-cells,
- vascular endothelium,
- reproductive organs,
- immune system,
- sensorial peripheral nerves and
- sympathetic nerves.
The CB2 cannabinoid receptor, is a G protein-coupled receptor from the cannabinoid receptor family that is encoded by the CNR2 gene in humans.
The distribution of CB2 receptors is quite different and mainly restricted to the periphery in the immune system cells, such as:
- T-lymphocytes and
- microglial cells.
Recently, CB2 receptor expression has also been shown in
- skin nerve fibres and keratinocytes,
- bone cells such as osteoblasts, osteocytes and osteoclasts,
- liver and
- somatostatin secreting cells in the pancreas.
The presence of CB2 receptors has also been demonstrated at the
- central nervous system, CNS,
- microglial cells and
- brainstem neurons.
There is evidence of staining with the CB2 antibody of human neurons. The presence of functional CB2 receptors is still debated. Recent evidences suggest that the CB2 receptor mediates emotional behaviours, such as schizophrenia, anxiety, depression, memory and nociception, supporting the presence of neuronal CB2 receptors or the involvement of glial cells in emotional behaviours.
Approximately 360 amino acids comprise the human CB2 receptor, making it somewhat shorter than the 473 amino acid-long CB1 receptor.
One other main endocannabinoid is 2-Arachidonoylglycerol (2-AG) which is active at both cannabinoid receptors, along with its own mimetic phytocannabinoid, CBD.
2-AG and CBD are involved in the regulation of such crucial metabolic functions as:
- immune system and
- pain management.
Cannabis has been used in herbal remedies for centuries. Scientists have identified many biologically active components in marijuana. These are called cannabinoids. The classical cannabinoids are concentrated in a viscous resin produced in the plant’s structures, known as glandular trichomes.
To create new hybrid strains of cannabis, male pollen is combined with the flowers of female cannabis plants. Thousands of combinations can be achieved in this way by cross-pollinating the tall Sativa plants with the fast-flowering Indica plants. The produced offsprings share the characteristics of both plants, including their content variations in psychoactive and non-psychoactive organic compounds.
At least 113 different phyto-cannabinoids have been identified from the Cannabis plant.
The three most studied components are the chemicals:
- -TetraHydroCannabinol (THC),
- CannaBiDiol (CBD), and
- CannaBiNol (CBN).
Tetrahydrocannabinol THC is the principal psychoactive constituent (or cannabinoid) of cannabis. It can be an amber or gold coloured glassy solid when cold, which becomes viscous and sticky if warmed.
Cannabidiol CBD is only one of the 113 active cannabinoids identified in Cannabis. It is a major phytocannabinoid, accounting for up to 40% of the plant’s extract. CBD is considered to have a wide scope of potential medical applications – due to clinical reports showing the lack of side effects, particularly a lack of psychoactivity (as associated with -THC), and non-interference with several psychomotor learning and psychological functions.
Cannabinol CBN is a weak psychoactive cannabinoid found only in trace amounts in Cannabis. Pharmacologically, relevant quantities are formed as a metabolite of tetrahydrocannabinol (THC). CBN acts as a partial agonist at the CB1 receptors, but it has a higher affinity to CB2 receptors, however lower compared to THC. Cannabinol has been shown to have analgesic properties, but modern production processes aim to minimize the formation of CBN.
11-OH-THC is also a metabolite of THC. The conversion from THC to 11-OH-THC is relatively high when cannabis is consumed in the form of cannabis edibles and, compared to oral consumption, lower when it is smoked or vaped. 11-OH-THC is more potent than THC and crosses the blood-brain barrier more easily.
Other phytocannabinoids are being studied.
The therapeutic index (TI) is an established clinical indication setting of an approved drug. It refers to the ratio of the dose of drug that causes adverse effects at an incidence/severity not compatible with the targeted indication (e.g. toxic dose in 50% of subjects, TD50) to the dose that leads to the desired pharmacological effect (e.g. efficacious dose in 50% of subjects, ED50).
The therapeutic index varies widely from one substance to another. The most forgiving among the opioid analgesics is Remifentanyl, which offers a therapeutic index of 33,000:1, while Diazepam, a benzodiazepine sedative-hypnotic and skeletal muscle relaxant has a less-forgiving index of 100:1 and morphine, a sedative, antidepressant, and analgesic of herbal origin (genus Papaver) has an index of 70:1 (still considered very safe).
A high therapeutic index means that the margin of safety exists between beneficial and toxic doses is great.
With regards to cannabis and alcohol, the therapeutic index is 1,000 and 10, respectively. This is the reason why some have advocated the prescription of cannabis as a medicine to combat chronic pain that cannot be treated by ordinary painkillers (eg. morphine).
The properties of cannabis are safer and more predictable compared to alcohol.
Although a plausible solution, simply legalising the use of cannabis for medical purposes will not make it a drug that is devoid of all danger. Indeed, the favourable therapeutic index of cannabis does not bring out its latent toxicity in case the substance is abused over prolonged periods of time (chronic use).
At high doses, cannabis can even induce panic attacks, mental aberration (paranoia) and hallucinations.
So is Cannabis a poison?
Sola Dosis Facit Venenum
“Everything is poison, there is poison in everything. Only the dose makes a thing not a poison.”
Paracelsus (1493 – 1541)
Since the 1940s, one rule of toxicology is the following:
The adverse effects of a poisonous substance are directly proportional to the dose being absorbed. Hence more poison, more dire effects… provided the dose is above a safe threshold. Below this no-effect level, nothing happens.
… Or does it?
This a paradox of toxicology…
The dose is the poison… or perhaps the cure.
Is Cannabis a Panacea?
Cannabis is the most commonly used illegal drug throughout the World.
Research of the cannabinoid system has many similarities with that of the opioid system. In both instances, studies into drug-producing plants led to the discovery of an endogenous control system with a central role in neurobiology.
Few compounds have had as much positive press from patients as those of the cannabinoid system. While these claims are investigated in disorders such as multiple sclerosis, spasticity and pain, basic research is discovering interesting members of this family of compounds that have previously unknown qualities, the most notable of which is the capacity for neuroprotection.
Large randomised clinical trials of the better known compounds are in progress. Even if the results of these studies are not as positive as many expect them to be, that we are only just beginning to appreciate the huge therapeutic potential of this family of compounds is clear.
Baker et al. 2003 ‘The Therapeutic Potential of Cannabis‘, The Lancet
In the meantime, reducing the risk to individuals remains obviously paramount. The science of toxicology may provide one step in that direction, by helping to teach members of our society what a lot of tribal people already have known for a long time.
Despite the associated health risks and social stigmas, mind-altering chemicals have been used for centuries in almost every cultures.
As such it would be unrealistic to expect that the recreational use of a popular drug like Cannabis will suddenly cease.