Post on 16-Dec-2015
Drugs, Poisons, Toxins
Drug - a substance that when taken into the body produces a physiological or psychological effects, usually by interfering with the body’s normal chemical reactions
Poison – a substance that when taken into the body produces death or physical harm, usually by interfering with the body’s normal chemical reactions
Toxin – a naturally produced substance that when taken into the body at very low doses causes death or physical harm, usually by interfering with the body’s normal chemical reactions
Ricin – a by product of castor beans
Drugs, Poisons, Toxins
How are they similar?• Must be taken into the body (inhaled, swallowed, absorbed, or
injected) for effect• Causes changes to the body by interfering with normal chemical
reactions• All can be poisons in the right dose
How are they different?• Drugs produce desired effects• Toxins are naturally produced, and cause damage at very low
doses
Examples?
“All substances are poisons. There is none which is not. The right dose
differentiates a poison and a remedy”
– Paracelsus 16th c. physician
Examples?
All drugs will become poisons at high doses. ● Tylenol, multivitamins, codeine, alcohol, etc.
“All substances are poisons. There is none which is not. The right dose
differentiates a poison and a remedy”
– Paracelsus 16th c. physician
Examples?
All drugs will become poisons at high doses. ● Tylenol, multivitamins, codeine, alcohol, etc.
Moreover, things that are typically considered toxins are sometimes therapeutic in the right dose. ● Arsenic is used to treat certain types of leukemia ● Botulin is used for botox, muscle spasms, crossed eyes, etc.
“All substances are poisons. There is none which is not. The right dose
differentiates a poison and a remedy”
– Paracelsus 16th c. physician
Determining Toxicity
There are 5 main things which determine the toxicity (adverse effects) of a poison:
1) The chemical form of the substance
2) How it enters the body
3) The victim’s age, weight, gender, and condition
4) Time period of exposure
5) Presence of other chemicals
Determining Toxicity
There are 5 main things which determine the toxicity (adverse effects) of a poison:
1) The chemical form of the substance
2) How it enters the body
3) The victim’s age, weight, gender, and condition
4) Time period of exposure
5) Presence of other chemicals
Example:
Arsenic, the metal, is not absorbed by the body, and so is not poisonous.
Arsenic compounds, such as As2O3 and As2O5, however, are readily absorbed and very toxic.
Determining Toxicity
There are 5 main things which determine the toxicity (adverse effects) of a poison:
1) The chemical form of the substance
2) How it enters the body
3) The victim’s age, weight, gender, and condition
4) Time period of exposure
5) Presence of other chemicals
Poisons can enter the body through inhalation, swallowing, absorption through skin or mucus membranes, or injection.
Determining Toxicity
There are 5 main things which determine the toxicity (adverse effects) of a poison:
1) The chemical form of the substance
2) How it enters the body
3) The victim’s age, weight, gender, and condition
4) Time period of exposure
5) Presence of other chemicals
Fetuses, the very young, the very old, and individuals in poor condition experience greater toxicity.
The greater the body weight, the less toxicity.
Women typically experience greater toxicity than men.
Determining Toxicity
There are 5 main things which determine the toxicity (adverse effects) of a poison:
1) The chemical form of the substance
2) How it enters the body
3) The victim’s age, weight, gender, and condition
4) Time period of exposure
5) Presence of other chemicals
Chronic exposure – toxin exposure occurs over a long period of time.
Acute toxicity – toxin exposure that is large enough to cause immediate serious problems
People with chronic exposure build up some tolerance to the poison, but will still experience ill effects
Determining Toxicity
There are 5 main things which determine the toxicity (adverse effects) of a poison:
1) The chemical form of the substance
2) How it enters the body
3) The victim’s age, weight, gender, and condition
4) Time period of exposure
5) Presence of other chemicals
Synergist - drugs are synergistic if their combined effects are greater than the sum of their individual effects (e.g. alcohol + some antihistamines)
Antagonists – drugs are antagonistic if taking them together reduces their individual effects
Measuring Toxicity
The toxicity of substances can be measured in animal trials.
• The poison is introduced to test animals at different dosages.
• The dose of poison that kills half of the animals exposed within a short time frame is LD50 (50% leathal dose).
Measuring Toxicity
Which substance is most toxic?
Why?
Botulin is most toxic because it is deadly in the smallest doses.
Measuring Toxicity
Which substance is most toxic? Why?
Not an easy question!
Green has the lowest LD50, and is the most toxic at high doses.
Red is most toxic at low doses.
Measuring Toxicity
Which substance is most toxic? Why?
Not an easy question!
Green has the lowest LD50, and is the most toxic at high doses.
Red is most toxic at low doses.
Doses where green is most toxic
Doses where red is most toxic
Calculating Dose Levels
TylenolLD50 rat = 3000 mg/kgRecommended maximum daily dose for adults: 4000 mg
1) What dose would be fatal for 50% of rats, if an average rat is 300g?
2) How much tylenol would a 150 lb person have to take to equal the LD50 dose (calculated for rats)? (Hint 1 kg = 2.2lb)
3) How many tylenol capsules would a 150 lb person have take to equal the LD50? (Hint 1 capsule = 500 mg)
Calculating Dose Levels
TylenolLD50 rat = 3000 mg/kgRecommended maximum daily dose for adults: 4000 mg
1) What dose would be fatal for 50% of rats, if an average rat is 300g? 90 mg
2) How much tylenol would a 150 lb person have to take to equal the LD50 dose (calculated for rats)? (Hint 1 kg = 2.2lb) 20,000 mg
3) How many tylenol capsules would a 150 lb person have take to equal the LD50? (Hint 1 capsule = 500 mg) 40 capsules
Calculating Dose Levels
CaffeineLD50 rat = 192 mg/kg
1) What dose would be fatal for 50% of rats, if an average rat is 325g?
2) How much caffeine would a 125 lb person have to take to equal the LD50 dose (calculated for rats)? (Hint 1 kg = 2.2lb)
3) How many No-Doz capsules would a 125 lb person have take to equal the LD50? (Hint 1 capsule = 100 mg)
Calculating Dose Levels
CaffeineLD50 rat = 192 mg/kg
1) What dose would be fatal for 50% of rats, if an average rat is 325g? 62.4 mg
2) How much caffeine would a 125 lb person have to take to equal the LD50 dose (calculated for rats)? (Hint 1 kg = 2.2lb) 13100 mg
3) How many No-Doz capsules would a 125 lb person have take to equal the LD50? (Hint 1 capsule = 100 mg) 131 capsules
Problems with LD50
Although LD50 trials are still used today, their use has declined over the last 20-30 years. Many people and organizations criticize LD50 trials both for their cruelty and their effectiveness.
Why might LD50 not be a useful measure of toxicity?• Animal studies have limited relevance to humans• We care about harmful effects, not just lethality• The toxicity of a substance varies greatly according to all
the factors discussed before (age, gender, condition, method, timing, other drugs, etc.)
Exit Ticket
1. Name 4 factors that affect the toxicity of a drug.2. Estimate the LD50 of the drug shown below.
3. The LD50 of ricin is 0.02 mg / kg. What does that dose correspond to in a 140 lb person? (1 kg = 2.2 lbs).
Homework
Toxicity Homework due next class
Bring materials to work on poisoner project next class – that project will be due 3/27