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May 25, 2010 5th HelMedica Issue  Article 5th
Review - Toxicology.
Title : CLASSIFICATION OF DRUG ADDICTIVE SUBSTANCES AND
MODE OF ACTION OF THE MOST COMMONLY ABUSED.
  

Author : Tsintou Magdalini*
Department : Medical School, University of Thessaly
*Editor in Chief, reviewer, webmaster.

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          1. Introduction.

          The therapeutic or "magical" properties of some plants are well-known since antiquity. Their use in religious ceremonies and sacraments mark the human encounter with the drugs. Since that time until today, with the help of technology, the pharmacologically active substances have been isolated from the plants and a plenty of new drugs has been composed in the laboratory. So from the coca leaves chewing, at present we've reached LSD and Ecstasy pills.

          In this article the drugs are classified into categories according to their mode of action and the most common of them in each category are referred (Table 1).

CLASSIFICATION OF DRUG ADDICTIVE SUBSTANCES

Illusinogens-Hallucinogens

1. LSD.

2. Morning glory seeds.

3. Psilocin and Psilocybin.

4. Bufotenin.

5. DMT.

6. DET (Diethyltryptamine).

7. DOM, STP (2,5-dimethoxy-4-methylamphetamine).

8. MDA (3,4-metylenedioxyamphetamine).

9. Mescaline.

10. Phencyclidine (PCP).

11. Cannabis products.

12. Khat.

 

 

Stimulants of the Central Nervous System

1. Methamphetamine hydrochloride.

2. Pemoline.

3. Fenfluramine.

4. Ritalin.

5. Caffeine.

6. Aminophylline.

7. Theophylline-Theobromine.

8. Cocaine.

9. Crack.

 

 

Suppressives of the Central Nervous System

1. Barbituric acid compounds.

2. Newer Non-Barbituric Hypnotics.

3. Benzodiazepines.

4. Meprobamate.

5. Methaqualone.

6. Chloral hydrate.

 

 

Inhalants

1. Solvents.

2. Aerosols.

3. Gases.

4. Nitrates.

 

 

Analgesic drugs-Opioids

1. Opium.

2. Morphine.

3. Codeine.

4. Heroin.

5. Pentazocine.

6. Apomorphine.

7. Buprenorphine.

8. Opioid antagonists.

9. Synthetic analgesic drugs.

 

 

Designer drugs

1. Amphetamine derivatives.

MDMA (Ecstasy)

MDE or MDEA

MBDB

4-MTA

2. Tryptamine and its derivatives

3. L.S.D.

4. Synthetic opiates (methadone, fentanyl, pethidine etc.).

5. Benzodiazepines.

6. Phencyclidine (PCP).

7. Methaqualone.

8. γ-hydroxybutyric acid (GHB).

 

 

Club drugs

1. MDMA (Ecstasy).

2. γ-hydroxybutyric acid (GHB).

3. Ketamine.

4. Flunitrazepam.

5. Methamphetamine.

 

 

             Table 1. Drug Categories for Substances of Abuse.

         
2.1 Illusinogens-Hallucinogens.

          2.1.1. Marijuana - Hashish.

          They are extracted from the seedling cannabis sativa. Marijuana comes from a specific variety (seven leafed) and it circulates only in the form of dried leaves while hashish additionally circulates also in forms that emanate after processing (plate, hemp oil). The main uptake-mode is smoking.

          The main active ingredient is Δ9-tetrahydrocannabinol (Δ9-THC), which acts on cannabinoid receptors in the brain and it increases dopamine release. The results of the cannabis use appear in about twenty minutes and last for 2-3 hours. By its action on the central nervous system (CNS) are caused inhibition of the short-term memory, reduced mental activity and difficulty in executing fine movements. The user has auditory and visual hallucinations, known as hashish-drunkenness or dreamy delirium, which may also be manifested as a panic reaction.

          People using cannabis are at risk for heart disease, vasopathies, obstructive pneumopathies, lung cancer and they exhibit a diminished perception, learning and memory capacity. The investigation of the dependence development and also the psychosis emergence in the chronic abusers is still in progress.

          In any case, the use of cannabis products, changes – often unexpectedly - the abuser thymic through auditory and visual hallucinations, and, therefore, the proposal which is occasionally heard for legalizing their use is completely unsubstantiated.

          2.1.2. LSD (d-lysergic acid diethylamide).

 

          It was randomly manufactured in 1938 in a Swiss laboratory. It chemically resembles serotonin and thereby it stimulates serotonin receptors in the brain, but without leading to a repressive action as the natural neurotransmitter does. It is commonly used orally and it quickly leads to tolerance and psychic dependence (after 3-4 uses).

          The symptoms appear about one hour after use and last 6-12 hours. Its action in the autonomic nervous system causes mydriasis, hyperglycemia, hyperthermia, and vomit while an overdose causes hypotension and bradycardia.

          From the CNS, the symptoms are mainly disorders of all the sensory organs and especially of the vision as well as disorders of space and time perception.

          The symptoms from the mental realm include thymic alternations from the euphoria state to a state of depression, loss of any organized thought or coordinated activity and panic attacks. In chronic abusers, the occurrence of a prolonged psychosis has been described and cases of paranoia or schizophrenia have been reported.

          2.2. Stimulants of the Central Nervous System.

          2.2.1. Cocaine.

 

          Cocaine is extracted from the leaves of the shrub erythroxylum coca, which grows in South America. The natives chewed the leaves usually along with calcareous materials in order to withstand hunger and physical fatigue.

          The first name of the coca leaves active ingredient was erythroxyline, while it was named cocaine by Wholer and Niemann who isolated it in a pure form in 1860. Its actions were studied in 1898 and its local anesthetic property emerged as well as its ability to cause euphoric feelings, mental activity, clarity and elimination of the fatigue feeling. So in the late 19th and early 20th century, cocaine was added in small amounts in various foods (wine, soft drinks) and was used in medicine. Very soon, the emergence of tolerance and dependence as well as the paranoid psychosis caused by its use were recognized. For these reasons, just in 1914, both trafficking and use of the cocaine was prohibited in America.

          Cocaine circulates as a white powder and it is usually sniffed by the nose because in the acidic environment of the stomach it is largely inactivated. Rarely, it is inhaled in cocaine vapor form, after having evaporated it previously in a special device.

          It acts on the autonomic nervous system by increasing the levels of adrenaline, noradrenaline and also serotonin due to the mono-amino oxidase (MAO) inactivation. The subsequent stimulation of the sympathetic nervous system, causes mydriasis, tachycardia, hyperpnoea and in higher doses it causes fainting, seizures, hyperthermia, cardio-respiratory function disorder and death.

          In the CNS cocaine inhibits dopamine re-uptake in the pre-synaptic membrane, resulting in a prolonged dopamine action in the nerve synapsis and the intense stimulation of neural circuits in the brain. The intense stimulation of the reward pathway causes to the abuser euphoria, logorrhoea, increasing sense of humor, hyperkinesis, increased libido and hallucinations in the form of pleasant visions. Very quickly, however, the abuser develops tolerance and dependence. The memory is weakening, the visual and auditory hallucinations cease being in a form of pleasant visions, the individual is suffering from insomnia, its libido is disappearing, becomes anxious, excitable, aggressive, it is falling victim to a persecution mania. Often paranoid psychosis of schizophrenic nature is appeared. Unfortunately, the collapse is complete at every level and the lesions caused in the CNS are essentially permanent. 

          2.3. Analgesic drugs - Opioids.

          2.3.1 Opium.

          Opium is produced by the immature flower pod of the plant papaver somniferum (soporific opium poppy). In China, the most well-known country in using opium, opium was imported in 1773 by the British Colonel Watson, who transported it from Persia and India. Given the very strong mental and physical dependence caused by its use, in a spread of one hundred years, one third of the major Chinese cities population was using opium.

          Opium contains about 25 active pharmacological substances (opium alkaloids), but the dependence is due to morphine and codeine.

          Opium can be taken orally (opium-phagia) but the main mode of its use is smoking in a special pipe. Action sites are the μ - opiate receptors in the brain, the cerebellum and the spinal cord. It causes mental stimulation, euphoria feeling, dizziness, confusion, analgesia, and drowsiness. A reduction of the perception, memory, consciousness level and a complete disorganization of the personality supervene. The abuser's picture is completed by anorexia, cachexia, persistent constipation, urinary retention, insomnia, decreased muscle tone, motor movement and speech disorders, double vision, etc. Death is due to the impaired cardiac and respiratory function. 

          2.3.2 Morphine - Heroin.

 

          Morphine was first isolated from opium in 1805 and owes its name to Morpheus, the son of Sleep, and the god of dreams.

          Heroin was manufactured randomly in a laboratory by morphine acetylation. Chemically, it is a diacetyl-morphine which easily crosses the blood-brain barrier, is distributed in large quantities in the CNS and is rapidly converted into morphine. It is essentially a more toxic and also addictive substance than morphine. It circulates as a white, crystalline, odorless powder. It is used intravenously and rapidly causes tolerance and addiction. Its action and also the symptoms it causes are similar to those of morphine.
          Morphine is a white, crystalline powder which can be used both orally and parenterally. It crosses the blood-brain barrier with difficulty and thus its concentrations in the brain, which is considered the site of its action, are small.

          It acts on the μ – opiate receptors in the brain, the cerebellum and the spinal cord and it causes euphoria feelings, dizziness, confusion, analgesia, and drowsiness. Its hypnotic and analgesic action, render it valuable to medical practice. However, its abuse results in tolerance and dependence and eventually the abuser course is the same as that described for the opium abuser. 

          2.4 Suppressives of the Central Nervous System.

          2.4.1 Barbiturates.

 

          Barbiturates are compounds of the Barbituric acid which is inactive by itself. They are divided into short-, medium- and long-acting compounds. They are used intravenously and orally and are distributed in the brain by crossing the blood-brain barrier.

          They act on the GABA-ergic neurons of the reticular formation and suppress the excitability of the nerves, the skeletal and smooth muscles like the heart muscle.

          By the barbiturates entry into therapeutics, the development of tolerance which they cause was rapidly emerged, as well as the dependence after chronic administration. The main symptoms of the chronic abusers are: weakness, drowsiness, tremor, anorexia, increased reaction time and reduced mental function.

          The tolerance and dependence caused by the barbiturates have reduced their use for therapeutic purposes. Their abuse by the drug addicts may be fatal when combined simultaneously with other drugs.

          2.4.2 Benzodiazepines.

          Benzodiazepines were synthesized in order to be used instead of the barbiturates. However, their use also results in tolerance and dependence. They are administered orally and act on the GABA-ergic neurons of the CNS. They cause drowsiness, blurred vision and mental function disorders while on high doses the neuromuscular synapses are excluded. Usually the insomnia management of the drug-dependent abusers, with the benzodiazepines use may be dangerous because of their simultaneous suppressive action along with another drug.

          2.5 Inhalants.

          2.5.1 Volatile Solvents.

 

          These are fluids contained in many industrial and household daily-use products (solvents, paints, glues, markers, etc.) and evaporate at room temperature.

          Inhaled they cause irritation of both the respiratory mucosa and the conjunctivas, but they enter the systemic circulation and because they are lipophilic molecules, they are widely distributed in the brain. They cause dizziness, euphoria, ataxia, speech disorders and in some cases hallucinations.

          Despite of the fact that the volatile solvents are numbering in the hundreds, different between them substances, the potential tolerance and dependence phenomena have not been studied sufficiently. The access to them is easy and is not limited by the current legal regime. In any case, it must be stressed that their toxicity in the liver, kidneys, lungs, also the immune, hematopoietic and central nervous system is important and in the long term it may lead to irreducible or even incompatible with life lesions.

         
2.6 Designer and Club Drugs.

          It is a group of drugs with various modes of action, but they are categorized separately because they are synthetic derivatives of laboratories and they circulate widely in places frequented by young people (Clubs). Among them are LSD already mentioned in the hallucinogens and the phenylethylamine derivative (MDMA), known as “Ecstasy” pill.

          2.6.1 MDMA.

 

          It is an amphetamine-type stimulant acting on the sympathetic nervous system by increasing the catecholamines levels.

          It is the main active ingredient in the 'Ecstasy' tablets, it is used orally and causes euphoria feelings, physical strength and emotions elation. However, the sympathetic system stimulation causes mydriasis, hypertension, tachycardia, perspiration, insomnia, nervous strain and hyperpyrexia especially dangerous since it leads to heat exhaustion and cardiovascular collapse. Its abuse leads quickly to tolerance and dependence phenomena.

         
3. Conclusions.

          The brief reference to some of the most well-known circulating drugs neither aims at providing lengthy pieces of information on substances that are already known to most of the people of any age worldwide, (is not to make more known some substances with which almost all ages of the entire planet are familiar nor at extensively covering the subject from a pharmacological point of view. It is an attempt to comprehensively review the most well-known drugs as regards the problems - mental and physical – induced by (resulting from) their use. These problems are briefly reported and summarized, and in no case do they constitute an excessive consideration of this matter. May the informative nature of this article show that the briefing on drugs is a responsibility of all of us. Both the society and the state, have the responsibility to protect people as a whole, and especially young people, by informing and convincing them that the drugs path accurately leads to the full mental and physical decay.


 

 

References:
NIDA (National Institute on Drug Abuse) http://www.drugabuse.gov/,
Ant. Koutselinis (Αντ. Κουτσελίνης), Εξαρτησιογόνες ουσίες, Parisianou Editions, 2002, ISBN : 960-394-112-3

 

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