Download TOXICOLOGY

TOXICOLOGY
• Is the study of the adverse effect of chemicals
on living organisms.
• All chemicals and drugs have some degree of
toxicity.
ROUTE OF CONTACT WITH THESE
CHEMICALS
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Inhalation
Oral
Topical
Self-injection
TARGET ORGANS
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Lungs via inhalation for gases, vapors
Liver for ingested chemical by mouth
Brain
Kidney
Heart
TOXIC ACTIONS
• Nonselective action
• Selective action: e.g., warfarin inhibiting
specific clotting factors
• Immediate actions: e.g., OP poisoning
• Delayed action: e.g., exposure to asbestos
OCCUPATIONAL AND SPECIFIC
ENVIRONMENTAL TOXINS
• A. Halogenated hydrocarbons: exposure is
through ingestion or inhalation.
• Carbon tetrachloride: contracted by consumption
of contaminated drinking water, inhalation (low
levels)
• Toxic effects: irritation of the eye and respiratory
system at low levels.
• Nausea, vomiting, stupor, convulsion, coma and
death from CNS depression at high levels
• Kidney and liver damage.
• Chloroform: by ingestion or inhalation
• Toxic effect: hepatotoxicity, nephrotoxicity,
arrythmias, nausea, vomiting, dizziness,
headaches and stupor.
AROMATIC HYDROCARBONS
• Benzene: half of exposure is via tobacco smoke,
combustion of fossil fuels including automobile
gasoline, consumption of contaminated water.
• Toxic effect: are hematopoietic toxicities
particularly leukemia (AML), agranulocytosis.
• Toluene: by automobile emissions, use of
toluene-like degreasers, certain paints and
furniture polish.
• Toxic effect: CNS depression, drowsiness, ataxia,
tremors, impaired speech, hearing , vision, liver,
kidney damage and death.
ALCOHOLS
• Methanol & Ethylene glycol: are oxidized to
toxic products.
• Formic acid- methanol
• Glyoxylic, glycolic and oxalic acid- ethylene
glycol
• Toxic effects: coma, seizures, hyperpnea,
visual loss (esp with methanol), hypotension
and nephrotoxicity (ethylene glycol).
• Antidote: fomepizole, IV ethanol
PESTICIDES
• Organophosphates and carbamate
insecticides: toxicity is via inhibition of AchE
resulting in accumulation of excess
acetylcholine.
• Antidote: atropine + pralidoxime
RODENTICIDES
• Exposure is by accidental ingestion or suicidal
ingestion e.g., warfarin.
HEAVY METALS
• Lead: exposure is by old paint chips, drinking water,
industrial pollution, food and contaminated dust
• Distributed to soft tissues, teeth, hair and bone where
it is detected by X-ray examination.
• Half life in blood- 1-2 months, in bone- 20 to 30 years.
• Toxic effects:
• CNS: headache, confusion, clumsiness, convulsion
coma & rarely death if treated with chelation therapy.
• GIT: constipation, intestinal spasm
• BLOOD: hypochromic, microcytic anemia.
• Still birth, decrease fertility.
• Antidotes: dimercaprol, succimer
• IRON: used as prenatal supplements and also
for the treatment of anemias
• s/s of iron poisoning: severe GI distress
leading to necrotizing gastroenteritis with
hematemesis and bloody diarrhea, dyspnea,
shock, coma
• Antidotes: deferoxamine IV, phlebotomy
• Mercury: forms;
• 1. Elementary mercury: exposure is usually occupational by
inhalation of the vapor.
• S/S: depression, tremors, memory loss, inflammation of the
kidneys, decreased verbal skills & pulmonary toxicity.
• 2. inorganic mercury: e.g., mercuric chloride, exposure is
usually occupational.
• Toxic effect: renal damage.
• 3. organic mercury: exposure is by ingestion of fish
contaminated with methylmercury, dyes, fireworks,
photography
• S/S: visual loss, loosening of teeth, paresthesias, ataxia,
hearing loss, tremors, mental deterioration & movement
disorders.
• Can be misdiagnosed as Parkinson's disease in the elderly.
• It is the most toxic of the 3 forms.
• Antidotes: activated charcoal, succimer and dimercaprol
• Arsenic: seen as wood preservatives,
pesticides, ant poisons
• s/s: gastroenteritis, hypotension, garlic
scented breath, torsades, rice water stool,
stocking glove neuropathy, skin
pigmentation(raindrop pattern)
• Antidotes: activated charcoal, dimercaprol,
penicillamine or succimer
GASES
• Carbon monoxide: colorless, odorless and tasteless
gas.
• Sources: combustion of carbon materials,
automobiles, poorly vented furnaces, fireplaces,
wood-burning stoves, charcoal grills and kerosene
space heaters.
• Toxic effects: is related to hypoxia within the brain
and heart. Dyspnea, lethargy, confusion, headache,
drowsiness, seizures, coma & death.
• antidote: removal of patient from source, 100%
oxygen by face mask or endotracheal tube.
• Cyanide: toxicity is as a result of inactivation of the
enzyme cytochrome oxidase.
• Toxic effect: death due to respiratory arrest .
• Antidote: nitrite, thiosulfate
• Asbestos: exposure is by inhalation of the fibers.
• Abestosis, mesothelioma and lung cancer are
associated with its exposure.
• Symptom: pain in the vicinity of the lesion,
dyspnea and cough.
• Silica: occupational, seen in mine workers,
construction sites and stone cutting.
• Is currently incurable.
ANTIDOTES
• Atropine: for intoxication by OP
• N-acetylcysteine: for acetaminophen toxicity.
• Sodium nitrite and sodium thiosulfate: for cyanide
toxicity.
• Fomepizole: for methanol or ethylene glycol toxicity.
• Pralidoxime: for organophosphate poisoning by
reactivation of acethylcholinesterase.
• CHELATORS:
• Dimercaprol: to chelate mercury ,lead and arsenic
• Succimer: for mild lead, mercury intoxication.
• EDTA: back up for lead intoxication.
• Penicillamine: copper, iron, lead, mercury