Symposium - Addiction Psychiatry Flashcards
What are the 2 mechanisms that explain why humans misuse drugs?
- Tolerance (the basis of physical dependence)
- Reward centre (the basis of psychological craving)
Of tolerance and reward centre, which is the basis of:
- physical dependence
- psychological craving
- Tolerance (the basis of physical dependence)
- Reward centre (the basis of psychological craving)
What is tolerance?
Tolerance = reduced responsiveness to a drug caused by previous administration
What are examples of drugs that tolerance develops in response to?
Develops in response to most but not all drugs, such as:
- Opioids, ethanol, barbiturates, benzodiazepines
What are the 2 mechanisms of tolerance?
- Dispositional tolerance
- Less drug reaches the active site
- Could happen due to
- Decreased rate of absorption
- Increased rate or metabolism to inactive metabolites
- Decreased rate of metabolism to active metabolites
- Increased rate of excretion
- Pharmacodynamics tolerance
- Drug has less action at the active site
- Down-regulation or internalisation of drug receptors
- Reduced signalling down stream of drug receptors
- Some other compensatory mechanism
- Drug has less action at the active site
WHat is dispositional tolerance?
- Less drug reaches the active site
What is pharmacodynamic tolerance?
- Drug has less action at the active site
What could dispositional tolerance happen due to?
- Decreased rate of absorption
- Increased rate or metabolism to inactive metabolites
- Decreased rate of metabolism to active metabolites
- Increased rate of excretion
What could pharmacodynamic tolerance happen due to?
- Down-regulation or internalisation of drug receptors
- Reduced signalling down stream of drug receptors
- Some other compensatory mechanism
What is tolerance closely related to?
Tolerance is closely related to dependence, as development of tolerance may also lead to withdrawal symptoms:
- About balance between drug and adaptive response
- When drug removed the adaptive response remains and so imbalance
- Dependent on drug to keep normal response
How does the effect of withdrawal of a drug usually compare to the effect of a drug?
Withdrawal phenomena:
- Withdrawal effect of a drug is usually the reverse to the acute effect
What is the acute effect and withdrawal effect of the following:
- opiod
- barbiturate
- cocaine
Where do neurons of the reward pathway project?
The reward pathway:
- Neurons project from the ventral tegmental area to the nucleus accumbens and prefrontal cortex
- When VTA neurons are stimulated dopamine is release
- This causes a sensation of pleasure/reward
What is released when VTA neurons are stimulated?
- When VTA neurons are stimulated dopamine is release
What does VTA stand for?
Ventral tegmental area
What is the reward pathway supposed to be activated by?
These exist to be activated by normal healthy behaviours that propagate genes:
- Eating, drinking and sex
What are examples of drugs that tap into the reward pathway?
Some drugs of abuse tap into reward pathway and increase dopamine levels to produce cravings:
- Heroin increases firing rate of dopaminergic neurons
- Amphetamine increases dopamine release
- Cocaine inhibits dopamine uptake
- Alcohol
How do the following drugs affect the reward pathway:
- heroin
- amphetamine
- cocaine
- Heroin increases firing rate of dopaminergic neurons
- Amphetamine increases dopamine release
- Cocaine inhibits dopamine uptake
What are the 2 distinct components of drug dependence?
So drug dependence has 2 distinct components:
- Physical dependence which develops as a consequence of tolerance to drug
- Psychological craving which is result of stimulation of the reward pathways in the brain
- Discriminative (cue) effects
- People taking drugs around the person
What are discriminative (cue) effects?
- Discriminative (cue) effects
- People taking drugs around the person
Different drugs have different associated risks, depending on what?
- Type of drug and effect
- Purity, dose, strength and tolerance
- Route of administration
- Legal status
- Comorbid health conditions
- Likelihood of dependency
- Methods of purchase
- Legal, prescribed, OTC, black market, internet
- Drug related deaths
What are the drugs with most impact on local health services and local communities?
- Alcohol
- Heroin/opiate misuse
- Benzodiazepine misuse
- Cocaine/crack cocaine misuse
What are examples of stimulants?
- Cocaine
- Amphetamine (also called speed)
- Methamphetamine
- Methylphenidate
For cocaine:
- mechanism
- administration
- effect
- problems
- withdrawal
- Cocaine
- Mechanism - monoamine reuptake inhibitor, increasing dopamine, serotonin and noradrenaline
- Administration – sniffed, inhaled
- Effect – stimulant and euphoria, anaesthetic effect, hypersensitive, increased alertness and energy, increased confidence and impaired judgement
- Problems – damage to nose and airways, convulsions with respiratory failure, cardiac arrhythmias and MI, hypertension and CVA, toxic confusion
- Withdrawal – depression, irritability, agitation, craving, hyperphagia, hypersomnia
