introduction to toxicology

Introduction to Toxicology

General toxicology
Define what is meant by the science of toxicology. Describe different areas of toxicology Classify toxic agents in groups. Explain factors affecting toxic responses. Discuss medicolegal aspects of poisoning.

What is toxicology? 

Is the study that relates the poison with its effects on the living. What is clinical toxicology? It is the science that deals with nature, action , symptoms and treatment of poisoning.

What are the areas of general toxicology? Forensic toxicology, environmental, occupational, experimental, developmental laboratory etc,

Factors affecting toxic responses

Factors related to the patient
Factors related to the poison
Stomach Age Tolerance Hypersensitivity.
Amount taken Route of administration Form of the poison Cumulation

Medicolegal aspects of poisoning

A case of poisoning is a medicolgal case. There are three categories of poisoning: ( Homicidal, suicidal and accidental). 3. Medicolegal duties of a doctor in suspected poisoning: - First, treat the patient - Suicidal cases or accidental do not necessarily require notification except if death occurs, but all cases of suspected homicide.


Medicolegal aspects of poisoning
No scope for professional secrecy Collect and preserve evidence of poisoning e.g. sealed samples biological fluids If a case dies Do not issue death certificate , notify the police who may require autopsy Detailed written reports of the case and keep in a safe custody Facing a case of food poisoning from a public eatery, notify the public health authority concerned.

Toxidromes

What is the meaning of toxidrome?
It is the syndrome caused by a specific type of poison Or the constellation of symptoms and signs resulting from any given poison How they can be helpful? May suggest the drug involved if the history is not reliable

What are the common toxidrome?

Anticholinergic Sympathomimetic Cholinergic Opioid Benzodiazepine

Anticholinergic syndrome

Symptoms: Dry m. m. , flushed skin, urinary retention, decreased bowel sounds, dilated irreactive pupil , cycloplegia and altered mental status { blind as a bat, hot as hades ,red as beet , dry as bone} Causes: Atropine, Antihistaminic,TCA, antipsycotic, Antiparkinsons, Amanita muscaria ( mushroom)

Sympathomimetic toxidrome

Symptoms: Dilated pupil, Hypertension, tachcardia, hyperpyrexia, agitation , diaphoresis (sweating), dilated pupils, tremors, arrhythmias convulsion and hypotension in severe cases.Toxic causes : Cocaine- Theophylline – Amphetamines , Caffeine- Ephedrine.

How to differentiate sympathomimetic from anticholinergic

Sympathomimetic
Anticholinergic
Symptom
Diaphoresis
Dry
Skin
Hyperactive
Inhibited
Bowel sounds
Absent
Present
Urine retention
Dilated reactive
Dilated irreactive
Pupil


Cholinergic toxidrome
Symptoms: Miosis.LacrimationUrinationDiaphoresis Vomiting – DiarrheaBronchorhea, bronchospasm, bradycardia

Cholinergic syndrome

Toxic causes: Organophosphates Carbamates Physeostigmine Neostigmine

Opioid syndrome

Symptoms: CNS depression Pinpoint pupil Respiratory depression Bradycardia, hypotension and decreased intestinal motility. *Reversed by Naloxone.

Opioid syndrome

Causes: Morphine and its derivatives Meperidine

Benzodiazepine toxidrome

CNS depression (altered consciousness) Rarely serious disturbed vital signs causes: diazepam.

Management

A. Decontamination B. Antidotes A. Decontamination: removal of the toxin from the patient or the patient must be removed from the toxic environment. 1. Emesis (vomiting): this induced with syrup of ipecac which causes vomiting by acting on the chemoreceptor trigger zone.



2. Orogastric lavage: by rinsing the patient’s stomach with water or saline lavage solution by means of a tube inserted through the patient’s mouth or nose.3. Activated charcoal: it binds many chemicals and prevents their absorption into the bloodstream and excreted together with the feces. Charcoal bind well to nonpolar drugs and toxins and binds poorly to polar substances.

4. Whole bowel irrigation: by flushing the entire GI tract with the intention of drastically reducing transit time (polyethyleneglycol) therefore, limiting the opportunity for toxins to be absorbed into the bloodstream. It must be employed soon after the toxin exposure has occurred. 5. Enhanced elemination: is also called ion trapping, acidification of the urine enhance the excretion of basic drugs while alkalizations of the urine enhance the acidic drug excretions.

6. Dialysis: is a process in which the blood is circulated through a bath in which a semipermeable membrane separates the components of the blood from the constituents. B. Antidotes: mean a medical intervention that is specific to a toxin and is effective only for that toxin or others closely related to it. Antidote is effective only once the toxin has reached the biological receptor.