VPT 421: Veterinary Toxicology (2+0)

TYPES OF POISONING

• Acute
  • Acute poisoning is associated with exposure to a relatively large, often single, dose of a toxic agent, this being followed by rapid manifestation of more severe clinical signs of intoxication.
  • It is also defined as sudden violent syndrome caused by a single large dose of poison.
• Sub-acute
  • In sub-acute poisoning the exposure level is lower and the survival time longer, than in acute poisoning, but the period between exposure and manifestation of signs of poisoning and possible death is again relatively short.
  • Symptoms of toxicity develop gradually.
  • In sub-acute toxicity studies, low doses of poisons are administered for a period of 90 days. These tests are performed to study, the No Observed Effect Level or No Observed Adverse Effect Level and to identify the specific organ(s) affected by the test compound after repeated administration.
• Chronic
  • Chronic poisoning is usually caused by multiple exposures to the poison, while individual quantities are not sufficiently large to produce clinical intoxication.
  • It is also defined as persistent lingering condition brought about by small repeated doses.
  • A relatively long delay is observed between the first exposure to the toxic agent and the eventual development of signs of poisoning.
  • Agents that cause chronic poisoning exhibit a cumulative effect. They either accumulate within the body or produce additive tissue damage. Once this level becomes critical, symptoms of poisoning develop.
  • In some cases, the development of symptoms of poisoning may be noticed many months after the exposure, even if there is no contact with the poison during the intervening period.
  • In the chronic toxicity studies, the exposure time is six months to two years for rodents and one year for non-rodents.