Symposium 3 - Addictions Flashcards
What mechanisms are involved with substance misuse?
Tolerance (dependence) Reward centre (cravings)
What is tolerance?
Reduced responsiveness to a drug caused by previous administration
Form of homeostasis
What are the mechanisms for dispositional drug tolerance?
Decreased absorption
Increased metabolism to INACTIVE metabolites
Decreased metabolism to ACTIVE metabolites
Increased excretion
What are the mechanisms for pharmacodynamic drug tolerance?
Down-regulation of drug receptors
Reduced signalling of drug receptors
What are the main mechanisms of tolerance?
Dispositional tolerance - less drug reaches active site
Pharmacodynamic tolerance - drug has less action at site
What is the mechanism of withdrawal?
Reverse of the acute effect of a drug
What is physical dependence?
Avoidance of withdrawal effects of a drug
What is the reward pathway?
Neurones project from ventral tegmental area to nucleus accumbens & prefrontal cortex
VTA neurones release dopamine
Leads to pleasure
What is the function of the reward pathway?
Reward the individual for eating, drinking and sex to encourage healthy behaviours
How does heroin effect the reward pathway?
Increases firing of dopaminergic neurones
How does amphetamine effect the reward pathway?
Increase dopamine release
How does cocaine effect the reward pathway?
Inhibits dopamine reuptake
How long do the modalities of cocaine take to onset?
Smoking - immediate
Injecting - 15-30s
Insufflating - 3-5mins
What are the recreational effects of cocaine?
Stimulant and Euphoriant Alertness and energy Confidence Impaired judgement Lessens appetite & desire for sleep
What are the harmful effects of cocaine?
Damage to nose/airways Convulsions Arrhythmias and MI HTN Toxic confusion Paranoid psychosis