Toxicology is the science dealing with properties, actions, toxicity, fatal dose, detection and estimation of, and treatment of poisons. Forensic toxicology: It deals with application of knowledge of toxicology for the purposes of law. It also includes the examination of the cases of poisoning in the living as well as the dead. Forensic Pharmacology: It deals with the legal regulation of the pharmaceutical industry, quality control of pharmaceutical products and its legal aspects such as medical product liability. Analytical Toxicology: It deals with laboratory analysis of poisons, primarily from biological samples.
Clinical Toxicology: It deals with diagnosis and treatment of cases of acute as well as chronic poisoning. Descriptive toxicology: It deals with the classification and description of poisons. Ideal homicidal poison: Characters: -Cheap, easily available, colourless, odourless and tasteless, -Capable of being administered in food, drink or medicine, without producing any obvious effects to prevent suspicion, -Highly toxic, -Signs and symptoms should resemble a natural disease or the serious ill effects should be delayed sufficiently long for the accused to escape suspicion.
Ideal suicidal poison: Cheap Easily available Highly toxic Tasteless or of pleasant test Capable of being easily taken in food or drink Capable of producing painless death – poisoning may result from: -the administration of a poison for criminal purposes -the swallowing substance by mistake for harmless substance -the inhalation through ignorance or accident, of the vapours of the poison -Accidental consumption of large doses of medicine containing a poison or incorrect preparation of medicines containing poisons. -excessive self-medication -addiction to drugs -bite by a poisonous animal.
-food infected with bacteria or their toxins Poisoning involves following four elements which represents the cause, subject, effect, and consequences of poisoning: Poison The poisoned person The injury to the cells, tissues or body organs, The consequences, namely either the symptoms and signs or death. The process of poisoning occurs in certain specific definite steps, which include: Firstly, the person has to be exposed to a toxic chemical or substance. Secondly, a toxic level of the chemical or substance has to be accumulated in the cells of the target tissue or organ.
Thirdly, the resultant injury to the cells should disrupt their normal structure or function. Fourthly, symptoms and toxic signs of poisoning then develop. Finally, if the toxicity is severe enough, death may result. Symptoms of poisoning- Poison is a substance of the nature of a drug, known to produce harmful effects and used to produce harmful effects. The harmful effect produced by a substance does not depend necessarily on the substance but the amount of the substance, the way in which it is administered and above all and specially the purpose for which the substance is administered.
One point is clear so far as the poisons are concerned. The substances should be inherently capable of proving harmful to the human body. Most of such substances are being utilised for purposes of treatment of diseases and come within the category of drugs, industrial agents, agriculture and domestic pesticides and insecticides. The main difference between drugs and medicines is intention to cause harm with knowledge of the capacity of the substance to produce harmful effect. In putrefied body poison belonging to organic origin is also likely to putrefy.
Whenever there is history of vomiting or diarrhoea it is incumbent on the doctor to preserve these for analysis. These should be preserved carefully and when necessary with the help of preservatives. (Secretions and excretions, contents of a stomach-wash. ) Vomiting is the first sign of consumption of anything that irritates the stomach e. g. Irritant poison. The type of vomit, smell, colour, presence of blood or necrotic tissues, often guide in determining the nature of poison. In some cases unaltered poisonous material is often detected.
Diarrhoea is a sign of irritation of the intestines in as much as vomiting is a sign of irritation of stomach. Classification of poisons According to the chief symptoms they produce—– corrosive: strong acids and alkalies HCL, H2SO4, HNO3, potassium nitrate carbolic acid sodium nitrate irritants: inorganic non-metallic—phosphorus (crackers firearms),chlorine, bromine, iodine(antiseptic).
Metallic- arsenic (colourless,odourless,tasteless),antimony,mercury,copper,lead,zinc, silver organic-vegetable——————————-castor oil seeds, croton oil, aloes, madar animal———— ———————cantharides, snake venom, insect bites mechanical—————————–diamond dust, powdered glass, hair. systemic: affecting the nervous system affecting the brain- somniferous: opium, barbiturates(sleep inducing) inebriant: alcohol, ether, chloroform (intoxicate) delirient: dhatura, belladona, cannabis indica(delirium, hallucin ation) affecting the spinal cord: nux vomica affecting the peripheral nerves: curare, conium affecting the cardiovascular system:
aconite, digitalis, oleander, tobacco, hydrocyanic acid affecting the respiratory system: poisonous irrespirable gases, –co2 ,carbon monoxide, H2s, methyl isocynide. Causes modifying the action of poison- A number of factors influence and modify the action of a poison. They include- Quantity- The administration of a large dose of some poison is sometimes followed by symptoms differing greatly in character from those, which follow a moderate dose; moderate doses of arsenic produce irritant symptoms, very large doses sometimes cause death without marked irritant symptoms.
Form –Poisons act most rapidly when in the gaseous state. Next comes the liquid state. If solid, the rapidity of their action depends on their solubility, i. e. , the more soluble a substance, the more rapidly will it get to work. Mechanical mixture with inert substances, e. g. dilution or mixture with inert substances, in some cases may alter the character of the symptoms. Mode of administration- This, by affecting the rate of absorption affects the rapidity of action of poisons.
Modes of introduction enumerated in order of rapidity of action, the most rapid first, are -injected into vein -application to a wound -introduction into a stomach -application to unbroken skin -application to a serous surface -injection into the rectum -application to the Tracheo-bronchial mucous membrane Condition of the body- Habit -This, in case of many poisons, e. g. opium, alcohol, and tobacco, tends to confer on the system a resisting power to the action of the poison, to the use of which the individual is habituated.
However all poisons do not confer an increased resisting power on the habitual user, e. g. chloral does not produce any marked tolerance.
Thus a person habituated to the use of chloral may die suddenly from the effects of a dose slightly in excess of that to which he is accustomed. Idiosyncrasy-This may show itself either in abnormal sensitiveness or the reverse to the action of a particular poison, e. g. mercury, or the individual may be exceptionally affected by a drug, e. g. purged by opium, or by some article of food. Disease- This, if the symptoms of the disease resemble those produced by the poison, tends to confer increased sensitiveness to the action of the poison, e. g. narcotics in advanced renal diseases.
If, on the other hand, the symptoms of the disease are opposed in character to those produced by the poison, diminished sensitiveness to the action of the poison may be the result, e. g. narcotics in tetanus. Sleep and intoxication-These may delay the action of poison. Accumulation-Small doses of a poison, each insufficient to cause any serious effect, if given one after the other at short intervals, may accumulate in the system and produce serious effects. Accumulation obviously tends to occur when the rate of elimination of the poison is slower than the rate of its administration.
Hence poisons, which are, only slowly eliminated from the body-e. g. lead and mercury, and metallic poisons generally-are especially prone to act as cumulative poisons. Organic poisons are, as a rule, quickly eliminated. In some, however- e. g. strychnine-the rate of elimination is comparatively slow, and accumulation tends to occur. – Routes of administration:- Poisons may gain entry into the body by various routes. These can grossly be considered as enteral routes (intestinal) and parenteral routes (by other means like intramuscular, injection, located outside the alimentary canal).
The poison may come in contact with the skin, mucous membrane of the respiratory tract, gastrointestinal tract, eye, ear, and the vagina. Routes of administration: Poisons may gain entry into the body by various routes. These can grossly be considered as enteral routes (through intestine)and parenteral routes (injection). The poison may come in contact with the skin, mucous membrane of the respiratory tract, gastrointestinal tract, eye, ear and the vagina. If the substance can not cross the mucous barrier and produce the effect at the site of exposure, it is considered as local effect.
For e. g. Corrosion Poisons have remote action, which can be specific and non-specific. Remote local action: localised to a definite organ. For e. g. alcohol de-toxication in liver Specific: the remote specific action of poisons results from the absorption of poisons into the system. For e. g. strychnine on spinal cord. Non-specific: poisons which possess a remote non-specific action on the system, produce thereby an effect similar to that, which often results from severe mechanical injury.
For e. g. extensive corrosion by corrosive acids may be followed by a shock. Post-Absorptive Behaviour of poison: Poisons once absorbed, can remain as such or in the form of metabolites within the body for variable periods. The poison, after absorption, is distributed to the various organs depending on the properties of the substance, blood supply to the organ and other factors. The process of biotransformation in the body may render the active substance into a more active metabolite, and it may result in toxic symptoms.
Depending on the rate of elimination of the poison, it remains in the body and will produce damage to the organs, where its distribution is maximum. Routes of elimination- Poisons are eliminated from the body either as such or in their modifications. The major channels of elimination are urine, faeces or excretions from the skin. Some poisons are also eliminated in the milk, and can be a source of poison for breast fed babies. Some poisons can also be delivered into saliva and other mucous or serous outflows.
These may either be excreted in the faeces, or may be reabsorbed, depending on the amount thus secreted. Treatment in cases of poisoning: —Removal of unabsorbed poison —Administration of antidotes —Elimination of poison by excretion —Symptomatic treatment -Removal of unabsorbed poison If the inhaled poison is a gas, the patient should immediately be removed into fresh air, and if necessary, artificial respiration should be started immediately by direct inflation, and oxygen should be given by means of a mask or nasal catheter at a rate of six to eight litres per minute.
If the poison is introduced subcutaneously into a limb from a bite or an injection, a tight ligature above the wound should be applied immediately and should be loosened every 10 or 15 minutes for 20 or 30 seconds to prevent the formation of gangrene. Ice or cold pack may be applied, and an attempt should be made to remove the poison by sucking, taking care that there is no abrasion or ulcer in the mouth. The injected site may be carefully cut open and the poison neutralise by a suitable antidote.
Acid and alkali burns should be flooded with water for 5minutes and 20 minutes respectively. If the poison is swallowed, it should be removed by gastric lavage, which is most effective if done within 2 to 5 hours of ingestion. This is done using a stomach tube or an ordinary, soft, non-collapsible rubber tube. – Use of antidotes Antidotes are agents, which counteract the effect of poisons. They are divided into non-specific and specific antidote. Non-specific antidotes with a mechanical action are those which render the poisons inert by their mechanical action e. g. activated charcoal.
Fats, oils and egg albumen prevent the action of a poison by forming a coating on the mucous membrane of the stomach, fats and oils should not be used for oil soluble poisons. Bulky food acts as a mechanical antidote to glass, as it prevents its action by imprisoning its particles within its meshes. Non-specific antidotes with a chemical action are those which counteract the actions of poisons by forming harmless or insoluble compounds, when brought into contact with them. Besides these, some drugs nullify the systemic effects of a poison and are useful in the treatment.
Such drugs have pharmacological effects on the organ or the system of the body, which are opposite to those produced by the poison. Chemical antidotes- counteract the effect of poisons-forms harmless and insoluble compounds-common salt, copper sulphate precipitates phosphorus. Mechanical antidote- make(neutralise) poisons inert, activated charcoal, fats, oils, egg albumin prevent by forming coating on the mucous membrane of stomach. Universal antidote-powdered animal charcoal+ magnesium oxide+ tannic acid.
Physiological or pharmacological antidotes-produce symptoms exactly opposite that of poison. Chelating agent-inactivate the metallic ion. -Elimination of poison by excretion Adequate intravenous fluids help the kidney to excrete poisons. Care should be taken not to over hydrate the patient, as it may lead to circulatory impairment or even pulmonary oedema. -Symptomatic treatment Pain, shock, peripheral circulatory collapse, water and electrolyte disturbance, asphyxia, coma, convulsions, anuria, hepatic failure and respiratory infections have to be looked after.