Psychology 2020A/B Chapter Notes - Chapter 2: Laissez-Faire, Nicotine, Tegmentum
22 May 2018
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Psychology 2020
Chapter 2
Drug Toxicity
- Toxicity – the physical or psychological harm that a drug might present to the user
- any substance has the potential for toxicity if the dose (amount) is high enough
- acute toxicity – the physical or psychological harm a drug might present to the user immediately
or soon after the drug is ingested into the body
o when there is a possibility that the SHORT TERM effects of the drug will trigger a toxic
reaction
- effective dose (ED) – the minimal dose of a particular drug necessary to produce the intended
drug effect in a given % of the population
- lethal dose(LD) – the minimal dose of a particular drug capable of producing death in a given %
of the animal population studied
- dose response curve - used to evaluate how much biological or behavioural response there is to
the given drug concentration
o the probability (0%-100%) that a certain dose of a drug will have its effect on a test
population
o ED response curve
▪ ex: ED50 means the effective dose for 50% of the test population to see the effect
▪ the # refers to the drugs effect on a specific proportion of the population being
exposed to the drug
▪ note: the curve looks at the properties of a specific drug effect not all the overall
properties of the drug itself
• so the drug may cause other effects, but each effect will have its own
dose response curve
o LD response curve:
▪ always on the right of the dose response curve bc it would require higher
dosage of the drug
▪ may overlap with the ED response curve
▪ ex: LD50 means the lethal dose for 50% of the population
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- therapeutic index : LD50/ED50
o aka therapeutic ratio
o gives us an idea of the drugs overall toxicity
o ex: if the therapeutic index is 9, you would need to take 9X the dose that would be
effective for 50% of the population in order to get a 50% chance of death in that
population
o this can be done in animals but is not ethical in humans
- toxic dose (TD): TD50/ED50
o amount that causes a sublethal side effect of the drug
o done in humans
- margin of safety: LD1/ED99
o the ratio bw the dose that produces death in 1% of the test population and the dose that
would be effective in 99%
o this ratio should be as high as possible
o the higher the ratio, the greater the difference bw effectiveness and lethality
o the wider the margin of safety, the safer (less toxic) the drug
- Canadian Center on Substance Abuse (CCSA) – federal program to initiate leadership and
solutions to Canadas alcohol and drug related issues
- Drug related emergency department (ED) visit – an occasion on which a person visits an
emergence department for a purpose that is related to recent drug use
o Ex: suicide attempts
o Ex: poisoning
o Ex: overmedication
- Polydrug use – drug taking behaviour involving multiple drugs
- Drug Abuse Warning Network (DAWN) Statistics - compiles data on drug related emergency
room visits and drug related deaths in public hospitals
o According to DAWN stats, cocaine and narcotic drugs are both highly toxic and are
usually taken with alcohol
o Recent concerns about increasing # of emergencies associated with club drugs and
opioid pain medication
o It is far more common for drug related deaths to be a result of polydrug use than
monodrug use
o Opioid drugs (heroin, morphine, methadone, or pain medication) is most frequently
reported drug involved in drug related death incident
o Cocaine is always in the top 3
o Alcohol and medications used to treat anxiety or depression is always in the top 5
o Marijuana is far less common
Judging Drug Toxicity from Drug-Related Deaths
- The fact that there are more instances of drug related deaths resulting from heroin use than
cocaine use UNDERESTIMATES the potential lethality of heroin, since there are far fewer heroin
users than cocaine users in north America
- The rare association of weed with a drug related death OVERESTIMATES its potential lethality
bc its used by a shit ton of people
- SO a judgement about the relative toxicity of illicit drugs requires an understanding of how
frequently the drug is used in the general population
- Ex: if all other facts are the same, if one drug produces 2X as many deaths as a second drug, but
the # of users of the first drug is twice that of the second, then the toxicity levels of the drugs
should be considered equal
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find more resources at oneclass.com
From Acute Toxicity to Chronic Toxicity
- Chronic toxicity – the physical or psychological harm a drug might cause over a long period of
use
o Ex: alcohol and tobacco
Behavioural Tolerance and Drug Overdose
- Tolerance – the capacity of a drug to produce a gradually diminished physical or psychological
effect upon repeated administrations of the drug at the same dose level
o Over repeated administrations, a drug dose needs to be increased to maintain an
equivalent effect
o Ex: caffeine
- The tolerance effect presents a possibility of death by drug overdose
- Overdose:
o Must look at the interaction bw the actual amount of the drug taken and the other
factors involved in the drug taking behaviour such as…
▪ # of previous times the drug has been taken
▪ setting within the drug taking behaviour occurs
- Behavioural tolerance – the process of drug tolerance that is linked to drug taking behaviour
occurring consistently in the same surroundings or under the same circumstances
o Aka conditioned tolerance
o Tolerance effects are maximized when the drug is taken consistently in the same
surroundings or under the same circumstances
o Based on Pavolvian conditioning
o Environmental cues in the room where the initial injections were given elicited some
form of effect OPPOSITE to the effect of the drug (it was the body getting ready for the
drug coming bc it was conditioned to know that this environment means the body is
about to receive the drug so it would produce effects opposite to the drug effects to
protect the body against dying from potentially high dosage levels)
o This is why former drug addicts are told to avoid the surroundings associated with their
past drug taking behaviour
▪ Environmentally induced withdrawal symptoms could increase the chances of
relapse
- There are also other mechanisms of tolerance (physiological changes that occur as a result of
repeated drug use):
o How neurons in the brain adapt to repeated high concentrations of drugs
o How enzymes in the liver can work more to break drugs down
Physical and Psychological Dependence
- 2 forms of dependence:
- Physical dependence:
o Based on the idea that the drug abuser continues the drug taking behaviour to avoid the
consequences of physical withdrawal symptoms
o Withdrawal symptoms show us that some kind of physical need develops over the
course of drug use
o Withdrawal symptoms are symptoms that are opposite to effects the drug originally had
o Ex: heroine is extremely constipating but eventually the body compensates for these
effects but when you suddenly stop it, you get diarrhea
- Psychological dependence:
o Based on the idea that drug abuser is motivated by a craving for the pleasurable effects
of the drug
o These people may even think they need the drug to function
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find more resources at oneclass.com
Document Summary
Canadian center on substance abuse (ccsa) federal program to initiate leadership and solutions to canada(cid:495)s alcohol and drug related issues. Drug related emergency department (ed) visit an occasion on which a person visits an. Polydrug use drug taking behaviour involving multiple drugs: ex: suicide attempts, ex: poisoning, ex: overmedication. The fact that there are more instances of drug related deaths resulting from heroin use than cocaine use underestimates the potential lethality of heroin, since there are far fewer heroin users than cocaine users in north america. The rare association of weed with a drug related death overestimates its potential lethality bc its used by a shit ton of people. So a judgement about the relative toxicity of illicit drugs requires an understanding of how frequently the drug is used in the general population. Chronic toxicity the physical or psychological harm a drug might cause over a long period of.
