Toxicology

Introduction

 Toxicology is a science dealing with properties, action, toxicity, fatal dose, detection, estimation and treatment of poisons.

 Toxinology refers to toxins produced by living organism which are dangerous to man. Like poisonous plant, venom of snake, spider, scorpion.

Contd…….

 Poison is a substance, which if introduced in living body, or brought in contact with any part through, will produce ill health or death, by its constitutional or local effects or both.

 Some poison are harmless in small quantity but produce death if large quantity is used.

Classification of poison according to symptoms they produces( mode of action)

A. Corrosive:-

1.

2.

Strong acids :- sulphuric acid, nitric acid, hydrochloric acid, acetic acid, carbolic acid, oxalic acid, salicylic acid.

Strong alkalis :- sodium hydroxide or caustic soda, potassium hydrochloride, ammonium hydrochloride.

3.

Metallic salts :- zinc chloride, potassium cyanide, ferric chloride, chromates of alkalis, bichromates of alkalis , Mercuric chloride etc

Contd…..

B. Irritants :-

1. Inorganic: a.

b.

Non-metallic:- phosphorus, halogen.

Metallic:- arsenic, antimony, mercury, copper, lead, zinc, silver. 2. Organic: a.

Vegetables:- castor oil, cotton oil.

b.

c.

Animals:- snake venom, insect bites.

Mechanical:- glass powdered, diamond dust.

Contd…..

C. Systemic:-

1. Cerebral: a.

CNS depressants:- alcohols, general anesthetics, opioid analgesic, hypnotics, sedatives.

b.

c.

CNS stimulants:- cyclic antidepressants, amphetamine.

Deliriant:- Dhatura, belladonna, cannabis, cocaine. 2. Spinal: nux vomica (strychnine), gelsemium.

3. Peripheral: conium, curare.

3. Peripheral: conium, curare.

4. Cardiovascular: aconite, quinine, tobacco , HCN, oleander, nicotine etc 5. Nephrotoxic : Oxalic acid, mercury, cantharides.

6. Hepatotoxic: Phosphorous, carbon, tetrachloride, chloroform

Contd……..

D. Miscellaneous :-

1. Insecticides: a. Organ phosphorus compounds: i. Alkyl phosphates: Hexaethyl tetra phosphate (HETP), Tetraethyl pyrophosphate (TEPP), Octamethyl pyro-phosphoramide (OMPA) ii. Aryl phosphates: parathion, diazinon.

b. Chlorinated hydrocarbons:- endrine, D.D.T. and gamaxin.

2. Antihistamines 3. Food poisons: Cl. Botulism, Mushroom poisoning.

Route of administration of poison:-

1.

2.

3.

4.

5.

Inhalation in gaseous or vapor form.

Injection into blood vessels(IV) Intramuscular, subcutaneous and intradermal injection.

Application to a wound(Ulcer) Introduction like oral, nasal, rectal, urethral, vaginal.

Route of elimination of poison:-

1.

2.

3.

4.

Kidney Skin Bile, milk, saliva, mucous and serous secretion.

Unabsorbed portion by vomit and faeces.

Factors modifying the action of poison

1.Quanity: Greater the quantity more severe would be symptoms of poison and usually rapid would be fatal.

2. Form of poison: The action of poison is influences by the form in which it is administered.

a.

Physical state: gas, liquid or solid.

b.

c.

Chemical combination: for e.g. arsenic is not poisonous but its salt arsenious oxide is poisonous.

Mechanical combination: for e.g. small dose of concentrated mineral acid produces corrosive action but same dose largely diluted with water is harmless.

3. Mode of administration: The rapidity of action of a poison depends upon the route of administration, rate of absorption and the mode in which it is introduce into the system. The route of administration may be enumerated as follows in order of rapidity of action: a.

Inhalation b.

c.

d.

Intravenous Intramuscular, subcutaneous, intradermal,rectal Oral 4. Condition of body: a.

Age: b.

Habit:- action of certain poison decrease with habituate. An addict can tolerate larger dose than a non addict. Like alcohol, morphine.

Antidotes

These are the substances which prevent or neutralize or counteract the action of poison.

Reasons of use of antidotes: 1.

2.

3.

The poison may not be completely removed by gastric lavage or the procedure is contraindicated.

The poison is already absorbed.

The poison has been administered other than ingestion.

Classification of antidotes: 1.

Mechanical antidotes or physical antidote.

2.

Chemical antidotes 3.

4.

Physiological or pharmacological antidotes Serological antidote

1. Mechanical antidotes :- acts by preventing absorption of poisons.

a.

Activated charcoal b.

Demulcents:- egg albumin, fats, oil.

2. Chemical antidotes :-they counteract the action of poison by forming harmless compound, when brought in contact with them.

a.

b.

c.

d.

Sodium sulphate for lead poisoning Copper sulphate for phosphorus poisoning.

Ferric oxide for arsenic poisoning.

KMNO4 for Opium and OPC

3

. Physiological antidotes :- these are the agents which act on the tissue of the body and produce symptoms exactly opposite to those caused by poisons. E.g.: a) Atropine, Pralidoxime for OPC b) Paracetamol poisoning: N-acetyl cystine c) Opioids poisoning: Naloxone d) Dhatura Poisoning: Neostigmine.

e) Strychnine Poisoning: Barbiturates.

4.

Serological antidote : Anti-snake venom

 Universal antidotes :- it is an antidotes that is used in those cases where the nature of the ingested poison in not known.

It has following composition: Activated powder charcoal or burnt toast---2 parts (absorbent) Magnesium oxide---1 part 9neutralises if poison is acid) Tannic acid or strong tea----1 part( precipitates alkalis)

Stomach wash/gastric lavage by Boas or Ewald’s tube

Chelating agent:-

These are soluble organic compound which fix metallic ions into their molecular form and make them inactivate. They form chelate with metallic poisons those are freely available in the circulation and their early excretion from the body through kidney.e.g.: 1.

2.

EDTA(ethylene diamine tetra acetic acid):-for lead.

Desferrioxamine:-for acute and chronic iron poisoning.

3.

4.

5.

6.

Bemigride:- barbiturate poisoning Nalorphine:- morphine, heroine poisoning.

Penicillamine (Cuprimine): Free metals Dimercaprol: For arsenic, mercury, copper, bismuth, gold.

Principle of management of poisoning

 The following principle should be followed in case of poisoning:-

1. Removal of unabsorbed poison from the body:-

a.

If inhaled:-take pt. to fresh air. Give oxygen and artificial respiration if necessary.

b.

If bitten or injected:- immediately apply tight band above the wound. Release in every 10 minutes for 20-30 second to prevent gangrene.

c. If local application:- it should be washing with water.

d. If ingested:- stomach wash/ gastric lavage within 3 hr.

2. Administration of antidotes

3. Prevention of absorption into the system:-

by a.

Renal excretion can be improved by plenty of fluid, diuretics.

b.

c.

d.

Increasing diaphoresis ( Perspiration) using neostigmine, pilocarpine By dialysis.

By chelating agents

4. Treatment of general symptoms:-

Pain, shock, peripheral circulatory collapse, electrolyte imbalance.

• • • •

Initial Management of the poisoned patient (ABCD’s)

First, the airway should be cleared of vomitus or any other obstruction and an oral airway or endotracheal tube inserted if needed.

Breathing should be assessed by observation and oximetry and, if in doubt by measuring arterial blood gases patients with respiratory insufficiency should be intubated and mechanically ventilated Circulation should be assessed by continuous monitoring of pulse rate, blood pressure , urinary output. An intravenous line should be placed and blood drawn fro serum glucose and other routine determinations Dextrose to treat hypoglycemia (0.5gm/kg)

History & Physical Exam

 Lab and Imaging procedures:  Arterial Blood Gases  Electrolytes: Sodium, Potassium, Chloride, Bicarbonate  Renal Function Tests: Blood Urea, Creatinine  Electrocardiogram

Decontamination

 Decontamination procedure should be undertaken simultaneously with initial stabilization, diagnostic assessment and lab evaluation  Decontamination involves removing toxins from the skin or GIT

A) Skin

 Contaminated clothing should be completely removed and double bagged to prevent illness in health care providers and for possible lab analysis  Wash contaminated skin with soap and water

B) GIT

1.

2.

3.

4.

– Emesis: Emptying of stomach in conscious children Syrup: Ipecac (6-12 months 10 ml single dose and >1 yr 15 ml) *repeated in 20 mins for those more than 1 yr.

– Gastric Lavage: 0.9% saline , Left Lateral position – – Activated Charcoal Catharsis: Laxative and purgatives Mannitol (1-2 gm/kg) Magnesium or sodium sulfate (200-300 mg/kg) * Specific Antidotes*



CONTRAINDICATION OF GASTRIC LAVAGE:

1.

Very old patients with esophageal varices.

2.

3.

4.

Poisoning with corrosives: danger of perforation of stomach.

Convulsant poisons: attempt of using tube may lead to convulsions Comatosed patients : risk for aspiration

CONTRAINDICATION OF EMESIS

 Corrosives and volatile poisons.

 Comatose patients.

 Heart disease patients.

 Pregnant women.

 Kerosene : may cause aspiration pneumonia.