Pathophysiology, treatment and Pharmacology Flashcards
what is tolerance
refers to either very short term or long term kiss if agonist efficacy
- mainly attributed to LTD within reward circuit
- dependence and addiction are associated with tolerance
describe how acute tolerance can be observed
can be observed rapidly (seconds to mins) during the course of a single episode of opioid intoxication
describe how long term tolerance is observed
more substantial and emerges after days to weeks of substance misuse
what does tolerance result from
results from adaptive mechanisms at the level of the drug target receptors
- desensitisation and internalisation
as well as at the cellular, synaptic and network levels
- downregulation of signalling components
what is dependence
compulsive craving that develops as a result of repeated administration of a substance of misuse, mainly due to the positive reinforcing action
what is drug addiction
an uncontrolled craving for a substance and is manifested in drug seeking behaviours
what is the most well established site of action of addictive drugs
the mesocorticolimbic dopamine system
what are the 2 main factors that substance misuse is mainly attributed to
- positive reinforcement- reward circuit
- avoiding negative effects- withdrawal
give examples of drug related harms of substance misuse
- damaging quality of life- social impact
- liver damage
- neuropathy
- respiratory complications
- CV complications
- infections
describe the pathophysiology of alcohol ethanol
- ethanol mainly acts via activating GABA receptors
- leads to overall inhibitory effect including inhibiting GABAergic neurons
- inhibiting GABAergic neurons lead to less GABA production
- means less inhibition to dopaminergic neurons (disinhibition)
- therefore, increases dopaminergic neutron excitation
- ethanol leads to synaptic plasticity for dopaminergic and GABAergic neurons
- tolerance is induced
- dependance and addiction start
outline the major alcohol related harms in substance misuse
- liver damage
- respiratory depression
- CV complications
- nervous system
- infection
how does alcohol substance misuse affect liver
accumulated acetaldehyde leads to
1. increase fatty acids and lipogenesis and hence fatty liver
2. the formation of free radicals and reactive oxygen species leading to liver fibrosis
how does alcohol substance misuse affect respiratory depression
- potentiates and mimics GABA action leading to inhibitory effects on respiratory centres
- respiratory failure
how does alcohol substance misuse affect cardiovascular system
causes hypertension, stroke, arrhythmia, cardiac hypertrophy
how does alcohol substance misuse affect nervous system
- depressing vital centres in the CNS
how does alcohol substance misuse affect infection
alcohol reduces key pulmonary defences against infection such as reducing mucociliary clearance, macrophage mobilisation and killing and clearance
explain why withdrawal effects occur in alcoholism
- mainly attributed to synaptic plasticity
- GABAergic receptors on dopaminergic and glutaminergic neurons are directly activated by high dose of alcohol
- this initially leads to suppressing of dopamine and glutamate release - LTP occurs in these suppressed neuronal synapses
- prolonged alcohol use leads to development of tolerance and physical dependance, which may result from compensatory functional changes by downregulation of GABA receptors
- therefore, alcohol is administered to calm and counteract the overexcited excitatory neurons
- in the absence of alcohol, withdrawal effects evolve by overstimulated potentiated and overstimulated dopaminergic and glutaminergic neurons
- leading to symptoms such as delirium and seizures
name the drugs that can be used to treat alcohol misuse
- disulfiram
- acamprosate
- naltrexone
- benzodiazepines
what is the mechanism of action of disulfiram
- irreversible inactivation of liver ALDH and increases acetaldehyde concentration leading to disulfiram alcohol reaction
- reducing alcohol induced CV complications
how does acamprosate work
- similar structure to that of amino acid neuromediators, such as GABA
- stimulates GABAergic inhibitory neurotransmission and antagonising excitatory amino acids, particularly glutamate
how does naltrexone work
- long acting specific opioid antagonist
- non aversive therapy and does not cause disulfiram like reactions
- reduces risk of a full relapse after having consumed a limited amount of alcohol and reduces the desire for alcohol during abstinence
what is the role of benzodiazepines
increases the inhibitory effects of GABA
- reducing neuronal excitability
describe the actions of methanol
- exerts similar CNS actions as ethanol
- exerts major health problems due to the metabolic product formaldehyde