What makes drugs of abuse psychoactive?
They can cross the blood brain barrier
In which 4 ways do drugs of abuse affect brain function?
What is the key feature of drugs of abuse that makes them addictive?
The user finds it rewarding and pleasant
Withdrawal= bad feeling
What two processes occur once you have been taking a drug repeatedly fro long periods of time?
Why does dependence occur?
Long term adaptive changes occur in receptors, transporters and second messengers etc.
What is withdrawal syndrome?
The unpleasant physical symptoms when an addicted person stops taking a drug of abuse
(means they want to take it again even more!)
How long after a person stops taking a drug of abuse can craving last for?
Why does withdrawal occur?
Uncompensated adaptive changes
(e.g. decrease in dopamine and increase glutamate levels)
What can cause dependence to occur?
Taking larger amounts for longer periods than origionally intended
(e.g. carry on taking opioids e.g. Morphine without pain)
Which characteristics of an individual who is dependant on a drug (7)?
- Express persistant desire to reduce substance use
- Spend a lot of time obtaining substance, using it and recovering from using
- Intense desire for substance (environmental cues)
- Impaired social performance (withdrawal from society & decreased ability to perform well at work)
- Risky use of substance (more likely to get caught)
- Withdrawal effects
N.B. wont see all in those who are addicted
What is habituation?
A reduction in response to a drug when the usual dose is taken (following continued presence of stimuli)
How does habituation lead to tolerance?
Individual must markedly increase dose to achieve the desired effect = keep taking more
How long does it take to start to build up tolerance?
4 days (less than a 50% response)
What is another name for metabolic tolerance?
How does metabolic tolerance work?
Alters the metabolism of a drug
(increases break down = lower concentrations left in body = less of an effect)
Which enzyme expression is up-regulated in repeated alcohol exposure (metabolic tolerance)?
= ethanol broken down faster = doesn't reach same levels in blood so less intoxication
What is another name for functional tolerance?
What happens in functional tolerance?
There is a change in drug target expression or sensitivity on the target cells
Give an example of functional tolerance
Excess use of opioid receptor agonists
= phosphorylation of opioid receptor = internalisation of receptor or uncoupling of G protein = presence of opioid has no effect as cannot bind or doesn't start cascade
How are receptors internalised?
It is held inside the cell in a vesicle membrane
By which process are receptors internalised?
Dynamin dependent endocytosis
What 3 things cause the type and intensity of withdrawal symptoms to vary?
- Amount of drug
What are the 7 main symptoms of withdrawal?
What is craving based on?
-> drug produces Euphoria and you want to feel the same way again= known as "substance dependant"
In which three ways does addiction cause problems?
- Drug harm (direct effects e.g. opiate respiratory depression & route of administration e.g. risk of HIV with IV use)
- Reduction in users ability to function normally (e.g. in social situations, problems at work = job loss = steal money)
- Cost to society!
Which drug causes the most harm to users and others?
Give 4 examples of opioid drugs that are drugs of abuse:
Give 4 examples of CNS depressants that are drugs of abuse:
Still activate reward pathway
Give two examples of anxiolytics and hypnotics that are drugs of abuse:
- Gamma-hydroxybutyrate (GHB)
N.B. both are moderate drugs of abuse... moderate dependency liability
Give 4 examples of Psychomotor stimulants (CNS stimulants) that are drugs of abuse:
- MDMA (ecstasy)
-> n.b. not psycologically or physically dependent