Drug dependence
Definition
A physical and/or psychological state, resulting from an interaction between a drug and organism, characterised by a compulsion to take the drug on a periodic or continuous basis to experience its psychic effects and/or avoid the discomfort of its absence
Psychological effects in dependence
wish
need
desire
craving
Physical effects in dependence
most marked with depressant
(inhibitory) drugs - opioids, alcohol
Addictive drugs
Depressants
(Psychological and Physical dependence)
Barbiturates
Opiates (heroin)
Alcohol
Stimulants
(Psychological dependence)
Amphetamines
MDMA
Cocaine
Cannabis
Hallucinogen
Inhalants
addiction mechanism
drug alters the physiological function of the organism and psycholigcal state of the subject
Continuous use develops tolerance
metabolistic or cellular
tolerance does not cause addiction,
but reinforces heavier or more frequent use
abstention from drug after abuse causes
physical and/or psychological withdrawal
patterns of use across countries vary depending on the availability of the chemicals and costs
Risk factors for drugs use
Dopamine & Reward
VTA
oppioids, alcohol, cannabis
Nicotine
works on nAChRs at the DA neurons in VTA
Mesolimbic (reward) pathway
Physical withdrawal
Psychological dependence
Non-addictive
Hypoxia
Glue
Solvents
Environmental
Genetic
Peer pressure
Unemployment
Childhood abuse
Formulation
mode of delivery
Personality traits
Impulse control
Risk-taking
Drug disposition
Pharmacokinetics
Pharmacodynamics
Psychopathology
Anxiety
Depression
Personality disorder
Stress responsivity
Drug induced neurochemical changes
work on inhibitory GABA neurons that
project to DA neurons in VTA
Anything that triggers release of DA
in the VTA can cause psychological addiction
DA neurons of the VTA projecting to the nucleus Accumbens
Cocaine & MDMA
work through blocking the uptake or increaseing
release of DA from presynaptic terminall
function of the reward system
reinforcing the positive behaviours
Sex
Food
Evidence for involvement
of DA in addiction
Intracranial stimulation in the VTA causes pleasure
D2 antagonists prevent that effect
Knock-out models
Physical dependence
normally inhibitory systems are balanced out by the excitatory systems
use of depressant drugs shifts that balance to the inhibitory side
abusing a drug causes the adaptation of the excitatory systems to match the the drug-induced levels of inhibition
Adaptation mechanisms
Receptor upregulation
increased NT synthesis
increased 2nd messenger concentrations
more depolarisations
Plasticity
Withdrawal
Withdrawal symptoms are the opposite
of acute effects of the drug
Caused by disrupted balance of inhibition/excitation (more excitation) in the absence of the drug
Heroin withdrawal
Withdrawal effects
Acute effects
Reflexes down
Secretions down
Feeling of warmth
Constipation
Cough down
Anxiety down
Aches and pains
Spontaneous muscle contractions (reflexes)
Tears, runny nose
Fever, goosebumps
Diarrhea
Coughing
Panicky
Heroin
effects mediated through the opioid receptors
in the forebrain, midrain and spinal cord
Alcohol
effects mediated through Ca2+ channels, GABARs and many other targets
very severe withdrawals
Pain relief
about 20% of patients stay clean after detox
association component
environment of the same friends or places, which were associated with drug abuse promotes the relapse
Anti-addictive therapy
Aversion theraphy
Substitution drug therapy
Clinical therapy
Methadone
Electric shocks used as a punishment for the drug use
Types of abusive drug users
Experimental
Recreational
Dependent
early stages
peers
choice
risk
Non-addictive
network
rules
mixed friends (users & non-users)
other life commitments
Addicts
experienced
friends are users
disrupted lifestyle
Soft/Hard
Soft
Recreational
Socially controlled
culturally conscious lifestyle
clubs, home use
Hard
addicted
Injecting
social and economic deprivation
inner city, street use
Reasons to try drugs
Availability
Curiosity
Peers
Context
Escape (for a while or forever)
Problems with the drug use
Infections (sharing needles)
Addiction
Cost
Drug habit is expensive, getting
the money often leads to crime
Social problems
Private and professional life
Mental problems
Psychosis, depression, anxiety
Revise drug mechanisms from 1st year notes