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Year 2 Brain and Behaviour > Drugs and Addiction (Laura) > Flashcards

Drugs and Addiction (Laura) Flashcards

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1
Q

Drug definition

A

A chemical substance, with a known chemical structure that. produces a biological and psychological effect when it is administered

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2
Q

How are drugs made?

A
  • Can come from plants or animals
  • Can be entirely synthetic
  • May be the result of genetic engineering
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3
Q

What is the key factor that makes a drug a drug?

A

Needs to be something that is administered to the body rather than a natural (endogenous) substance released by the body

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4
Q

What is pharmacokinetics?

A

The branch of pharmacology concerned with the movement of drugs within the body

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5
Q

How does route of administration affect pharmacokinetics?

A
  • Causes drastic differences in onset, intensity and duration of a drug’s effect
  • Slower onset of drug action the more gradual the build up of the effect and the longer it will last
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6
Q

How is a route of administration chosen?

A
  1. Chemical characteristics of the drug
    - Unprocessed drugs such as tobacco or cannabis cannot be injected only smoked, snorted and cooked
  2. Personal preference
    - Disliking sensation of inhalation
  3. Speed with which the drug acts
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7
Q

How are health outcomes associated with route of administration?

A
  1. Risk of dependence - the sooner the effect of the drug is experienced the more reinforcing it is
  2. Susceptibility to infection - intravenous could lead to Hepatitis C
  3. Route specific health complications - snorting can lead to nasal ulcerations
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8
Q

Route of administration: Rural Vs. Urban Drug Users (study)

Young, Havens and Leukefeld (2010)

A
  • 212 rural users vs 111 urban users
  • Prescription drug. abuse (e.g OxyCodone)
  • Urban users more likely to swallow drugs
  • Rural most likely to snort drugs
  • Alternative routes of administration were more likely in rural populations
  • Linked to drug problem severity (higher in rural populations)
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9
Q

How does absorption into the bloodstream account for some differences in pharmacokinetics? (and distribution of drug after absorption)

A
  • More barriers a drug has to travel through too reach the brain the slower the effect and drug more likely to be degraded
  • Degree too which drug is soluble in lipids
  • Degree of ionisation (ionised forms less likely to cross cellular membrane than deionise)
  • Size of molecule (smaller = faster)
  • Difference in drug concentration on either side of membrane
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10
Q

Examples of absorption at different routes of administration

A
  1. Intravenous = Little absorption, direct delivery to the blood stream and move to site of drug action
  2. Inhalation = Difference in chemical concentration from lung to blood stream always high, so rapid (movement down the gradient), high lipid solubility and small particles
  3. Mucous membrane = Several layers of cells to cross but aided by difference in concentration
  4. Oral = very slow, often poor because of degradation by stomach acid and enzymes
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11
Q

How are drugs distributed after absorption?

A
  1. Stored in body tissue
  2. Remains in blood stream
  3. Metabolised
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12
Q

What does an agonistic drug do to neurotransmission?

A

Drug that binds to receptor and switches neuron on

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13
Q

What does an antagonistic drug do to neurotransmission?

A

Drug that binds to receptor and prevents agonists from binding and neuron won’t switch on (drug blocker)

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14
Q

What are the monoamines?

A
  • Neurotransmitters
  • Dopamine
  • Serotonin
  • Norepinephrine
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15
Q

What are the 2 main process that contribute to drug elimination?

A
  1. Metabolism
  2. Excretion
  • The body works actively to eliminate the drug
  • Reverse of absorption
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16
Q

How are drugs excreted?

A
  • Drugs can be excreted. either unchanged or as a metabolite
  • Via. many different wxit routes, urine, bile, exhalation, sweat, saliva etc
  • The most important organ in excretion is the kidney
  • Drug molecules that cross membranes easily can be accidentally reabsorbed so products that are most easily
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17
Q

Mode of drug excretion: Exhalation (Lungs)

A
  • Example of the importance of principles of diffusion
  • When being excreted the concentration gradient works in the opposite direction to absorption
  • Lungs should have low concentration so drug moves from blood stream to lungs
  • Every time breathe out drug is excreted
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18
Q

How does the metabolism break down drugs?

A
  • Breaks them down into metabolites
  • Breaks them down into another chemical that can be active (can also create biological or psychological effects) or inactive
  • Tends to take place in the liver
  • Phase 1 (oxidation), phase 2 (conjugation) (and phase 3)
  • Doesn’t always go in the expected direction
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19
Q

Metabolism example: Alcohol

A
  • Alcohol is metabolised by specific enzymes in the liver
  • Constant rate (170-240g per day average)
  • Alcohol to acetaldehyde to acetate to water and carbon dioxide
  • Important area of research is individual differences in alcohol metabolism
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20
Q

What is the half life of a drug?

A
  • The amount of time it takes to eliminate half the drug
  • Reflects time to metabolise and excrete
  • Affects how long the effects of drug will last
  • Time interval to avoid withdrawal
  • Caffeine has a half-life of 3-7 hours
  • Half-life can vary from person to person (e.g. weight, gender etc..)
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21
Q

Journey case study: MDMA (route of administration)

A
  • Oral
  • Intravenous
  • Intranasally
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22
Q

Journey case study: MDMA (absorption)

A

Gastrointestinal tract

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23
Q

Journey case study: MDMA (Onset of action)

A

30 minutes

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24
Q

Journey case study: MDMA (Peak serum levels)

A

1-3 hours

25
Q

Journey case study: MDMA (Distribution)

A

Passes readily int tissues

26
Q

Journey case study: MDMA (Site of action)

A
  • Indirect serotonergic agonist
  • Increasing the amount of serotonin released into the synapse
  • Enhances the release of dopamine and noradrenaline
  • Can block their re-uptake
27
Q

Journey case study: MDMA (Metabolism)

A
  • In liver to an active metabolite

- Methydioxyamphetamine

28
Q

Journey case study: MDMA (Excretion)

A
  • Urine
  • Unchanged drug
  • Phase 1 and 2 metabolites
29
Q

Journey case study: MDMA (half-life)

A

7 hours

30
Q

What is neuroadaption?

A
  • When we introduce drug to the brain we upset its balance
  • Brain seeks to adapt to redress this imbalance by minimising the effect of the drug
  • Brains version of homeostasis
31
Q

What is tolerance of drugs?

A
  • When we use a drug repeatedly the effects diminish
  • We need more and more to get the same effect as when we first used it
  • Tolerance is to effects of drug and not drug itself
  • Applies to almst all effects associated with drugs of abuse
  • Happens at different rates and to varying extents for different effects of those drugs
32
Q

What effects of drugs do we usually become tolerant to the quickest?

A

Negative effects e.g. nausea

33
Q

Tolerance case study: heroin

A
  • Quick tolerance to nausea
  • No tolerance ever to constipation or ‘pinpoint’ pupils

CROSS-TOLERANCE: Once you are tolerant to effects of heroin you are also tolerant to effects of morphine, codeine and methadone. Tolerance to effects of one drug in a class leads to tolerance of effects of other drugs in the class

34
Q

What is metabolic tolerance

A
  • Pharmacokinetic tolerance

- Body becomes better and more efficient at breaking the drug down (small effects)

35
Q

Metabolic tolerance example: Alcohol

A

Amount of liver enzyme produced by body goes up

36
Q

What is cellular tolerance?

A
  • Pharmacodynamic tolerance

- Change in number of receptors, in receptor function and/or post-synaptic function (large effect)

37
Q

Cellular tolerance example: Caffeine

A
  • Changes in adenosine receptor signalling that oppose effects
38
Q

Tolerance and drug overdose

A
  • Overdose often happens when people are on the road to recovery
  • Tolerance has gone down but individuals use a habitual amount and that habitual amount is too much following abstinence or reduction
39
Q

What is sensitisation?

A
  • Opposite of tolerance
  • After repeated administration it will take less of a drug to elicit the same effect
  • Cross-sensitisation can also occur e.g. cocaine and amphetamine
  • Thought to be due to persistent activation of ventral hippocampus-nucleus accumbens pathway
40
Q

How does physical withdrawal syndrome occur

A
  • Due to neuroadaptation (tolerance)
  • As drug wears off uncomfortable symptoms occur
  • Reversed by administering drug
  • Sign of physical dependence on a drug
41
Q

What factors affect withdrawal?

A
  • Pattern of drug use
  • Amount of drug consumed
  • Length of time using drug
  • Half-life
42
Q

Evidence for caffeine withdrawal study

Silverman, Evans, Strain and Griffiths (1992)

A
  • Double-blind trial
  • Two days of their normal caffeine regime
  • Two days with placebo pills
  • Two days with. caffeine pills
  • Assessed depression level, anxiety, mood state and incidence of headaches
  • Significantly higher scores in these tests in the placebo condition than in either of the other conditions
43
Q

What is the withdrawal-reversal hypothesis

A
  • When baseline cognitive performance levels are taken at the beginning of a trial, experimenters are actually misinterpreting withdrawn performance as normal
  • James (1997) suggested a long term repeated measures trial with suitable ‘washout’ periods between testing
  • James (1998) failed to find any net benefits of sustained caffeine usage
44
Q

What is learning theory?

A
  • Dominant approach to understanding addictive behaviour
  • Helpful way of exploring non-drug addictions

Two variations:

  1. Learning theory
  2. Social learning theory
45
Q

How does learning theory work?

A
  • Operant conditioning
  • Understanding behaviour in terms of rewards and punishments resulting from that behaviour
  • Assumption that we will tend toward reward and avoid punishment
46
Q

Positive reinforcement for drugs (operant conditioning)

A
  • Taking the drug leads to activation of reward pathway
  1. Contiguity - how clearly the behaviour and the effect are linked (time)
  2. Routes of administration - how soon you feel effects = more reinforcing because behaviour and effect are more clearly linked (time)
47
Q

Negative reinforcement for drugs (operant conditioning)

A
  • Removal of unpleasant stimulus/discomfort

- Removal of withdrawal symptoms (nausea, headaches etc)

48
Q

Punishment for drug (operant conditioning)

A
  • Negative consequences of behaviour
  • Withdrawal, health consequences
  • Can often be in medium and long term in cases of addictive substances
  • Often lower or low contiguity
49
Q

What is conditioned tolerance?

A
  • Drug opposite conditioned responses counteract. anticipated effects of drugs
  • This may contribute to tolerance
  • Attenuate drug effect
50
Q

What is conditioned ‘high’ needle- freaking

Levine (1974)

A
  • Heroin users when heroin is unavailable
  • Go through ritual of preparing to inject drug but use saline (or other things) instead
  • Mild ‘high’, some physiological signs, some withdrawal reversal
51
Q

What is social learning theory?

A
  • Learning always takes place within a social context (Bandura, 1977)
  • Self-efficacy, the extent to which someone feels capable of an action (Bandura, 2010)
  • Expectancy theory (expectation of an outcome) especially relevant in alcohol research (Jones et al 2001)
52
Q

Animal model pros

A

Helps us to understand neuroadaptation, risk factors for addiction and development of treatments.

53
Q

Animal model cons

A
  • Led us down wasteful routes
  • Many drugs based on animal models have failed.
  • Animal models portray addiction as a disorder of compulsion but human evidence suggest goal-directed operant behaviour
  • Addiction: dependence on language
  • Cannot ignore environmental and social: hard to model with animals
54
Q

What is the incentive sensitisation theory based on?

Robinson and Berridge (1993)

A
  1. Craving
  2. Craving and drug taking can. be re-instated after drug use has ceased
  3. As drugs are wanted more and more, liking may go down
55
Q

What is polydrug use?

A

The use of more than one drug in combination

56
Q

Why is there polydrug use?

A
  • Cumulative or complementary effects: mixed to increase overall psychoactive experience
  • Offsetting of negative effects of a drug
  • The use of several substances by an individual over a longer period of time might reflect the replacement of one drug by another, due to changes in price, availability, legality or fashion
  • Could also reflect the use of separate drugs in different settings or contexts, or simply reflect regular multi-substance use associated with drug dependence
57
Q

What is the underlying neurobiology of polydrug use?

A
  • Common neural systems
  • Use of one drug leads t risk of using another
  • Cocaine addict at risk of relapse from occasional heroin use and vice versa
  • Rehab requires total abstinence
  • Cross sensitisation exists between non-drug and drug based addictions
  • Sex addicts are often addicted to alcohol or another drug
58
Q

Heroin and cocaine co-use

A
  • Negative consequences on health
  • Simultaneous. use doesn’t induce novel effects
  • No difference in reinforcement value, especially at high doses
  • Cocaine alleviates withdrawal effects of opioid use

Year 2 Brain and Behaviour (4 decks)

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