Basics Of Toxicology Flashcards
What is toxicology?
The science that relates adverse effects of chemicals, including drugs, to biological systems
Acute toxicity arises from what?
A single or multiple exposure to an agent over 1-2 days
Subacute toxicity occurs from what?
Repeated exposures of an agent over a period no longer than 3 months
Chronic toxicity occurs from what?
Repeated exposures over a period greater than 3 months
What is synergism in toxicodynamics?
when 2 drugs with the same effect are used together, and produce a greater response than what would be expected by adding the responses of each drug used alone
How does volume of distribution (Vd) of a toxin affect the ability to purify it through hemodialysis? (toxicokinetics)
The larger the Vd, the harder it is to purify because the toxin is accumulated in the periphery
What happens to the elimination process at very high and toxic concentrations? (toxicokinetics)
Elimination process may become saturated and toxins/ drugs normally eliminated by 1st order kinetics are now eliminated by 0 order kinetics
What are the primary determinants of toxicity?
- hazard vs risk
- dose/ dose rate
- duration of exposure (AUC)
- route of exposure
How do different routes of exposure affect toxicity?
IV > inhalation > IM > SC > oral > topical
What is biomagnification?
The increase in concentration of toxins from small to large sources/ organisms (ex. phytoplankton vs herring gull)
What are the 2 basic mechanisms of oxidative toxicity and cell death?
- compounds bind directly to cellular components and interfere with normal cell function causing oxidative stress (CO, cyanide, lead)
- compounds undergo redox cycling in the presence of oxygen increasing the formation of ROS (paraquat)
What is necrosis and how does lack of a proper immune response contribute to this process?
The acute, traumatic premature death of cells in living tissue caused by external factors
Lack of a proper immune response leads to a buildup of dead tissue and cell debris
What is apoptosis?
A “programmed” mode of cell death (“cell suicide”)
Apoptosis can occur in what 2 fashions?
Naturally (to benefit an organism) or induced by the chronic exposure to certain toxins
What 4 treatments are used for acute poisoning?
- gastric lavage
- activated charcoal (absorbs toxins)
- induced emesis (ipecac syrup)
- increase the rate of excretion
Under what circumstances is gastric lavage not recommended?
After 4 hours or if:
- 30 min have elapsed since ingestion of corrosive material
- hydrocarbon solvents have been ingested
- coma, stupor, delirium, or convulsants are present
How can you increase the rate of excretion as a way to treat acute poisoning?
- osmotic diuretics
- alter urinary pH (bicarbonate, ammonium chloride)
- hemodialysis and hemoperfusion
What is the rule of thumb for dialysis?
Smaller the Vd, more effective the dialysis
What drugs act to reduce absorption or enhance elimination?
- activated charcoal
- ammonium chlorine
- sodium bicarbonate
What drugs act to chelate metals?
- dimercaprol: arsenic
- penicillamine: copper poisoning (Wilson’s disease, resistant rheumatoid arthritis)
- deferoxamin: iron poisoning
- calcium disodium edetate: lead poisoning
What drugs act to inactivate toxins?
Acetylcysteine- acetaminophen poisoning
What is the mechanism of bleach poisoning?
Oxidative stress