1b Psychopharmacology for psychiatry Flashcards
targets for psychiatric medicines
receptors
neurotransmitter reuptake sites
ion channels
enzymes
how are psychiatric drugs classified?
based on chemical structure
based on illnesses they treat
based on pharmacology
pros/cons of grouping drugs based on chemical structure?
WHO classification system
pro - each drug has unique structure so easy to allocate data
con - no use in clinical decision making
pros/cons of grouping drugs based on illnesses they treat?
pro - easy for Dr to choose drug as they make diagnosis
cons - many medicines work for several disorders, many psychiatric disorders have multiple symptoms, one drug may not treat them all
multiple symptoms may be based on different neurotransmitter systems
how is grouping drugs based on pharmacology done?
neuroscience based nomenclature, targets neurotransmitters
what is the only NT not taken back up by cell
Ach acetylcholine
acetylcholinesterase breaks it down
what is a neuron auto-receptor?
usually inhibitory, activated by neurotransmitter it releases inhibits calcium influx switches off firing of terminal reduces neurotransmitter release (autoregulating neuron firing)
what is the most common form of psychiatric drug? give an example
blocking enzyme activity
MOAIs for anxiety/depression block breakdown of serotonin and NA
acetylcholinesterase inhibitors for dementia
lithium blocking glycogen synthase kinase for mood stability
give examples of receptor targeting psychiatric medicines
dopamine receptor blockers - schizophrenia
serotonin receptor subtype antagonists - depression
histamine receptor antagonists - sleep/insomnia
benzodiazapines - enhance GABA for sleep
guanfacine - enhance NA for ADHD
how do reuptake targeting medicines produce effect?
most neurotransmitters are recycled via reuptake sites
drug blocks reuptake site
increases neurotransmitter concentration in synapse
enhances post-synaptic receptor activity
e.g citalopram SSRI
reuptake targeting drugs examples
citalopram SSRI
desipramine - NA reuptake inhibitor (depression)
methylphenidate - dopamine reuptake inhibitor (ADHD)
amfetamine - ADHD swithces reuptake site direction to enhance release
key neurotransmitter system in psychiatry and its receptors
5-HT
post synaptic 5-HT1A inhibitory, reduces downstream firing
5HT2A implicated in psychadelic drugs
ion channel targeting psychiatric medicines examples (and channels targeted)
Na channels sodium valproate and carbamazepine - epilepsy and mood stabiliser
Ca channels - gabapentin, pregabalin - epilepsy and anxiety
how are neurotransmitters categorised?
fast acting - on/off switches (effects on content e.g memory, movements)
slow acting - modulation - not on/off as too slow (effects on emotions/drives)
examples of fast acting neurotransmitters
excitatory - glutamate from pyramidal cells
inhibitory - GABA from inter-neurons
examples of slow acting neurotransmitters
only 5% of neurons dopamine serotonin acetylcholine noradrenaline endorphins
drug classes that treat depression
MAOIs TCAs SSRIs SNRIs receptor antagonists
impact of excess glutamate in psychiatric disorders and its treatment
epilepsy - perampanel
alcoholism - acamprosate, ketamine
impact of GABA deficiency in psychiatric disorders and its treatment
anxiety
treated by benzodiazapines (gaba enhancers)
impact of 5-HT deficiency in psychiatric disorders
depression and anxiety
MAOIs and SRIs
role of excess dopamine in psychiatric conditions and their management
psychosis
dopamine receptor blockers
role of excess noradrenaline in psychiatric disorders and management?
nightmares
prazosin - blocker
role of acetylcholine deficiency in psychiatric disorders and management?
impaired memory/dementia
acetylcholinesterase enzyme blockers
what is a partial agonist?
lower max efficacy than full agonists
has improved safety - overdoses
can act as antagonist in states of high neurotransmitter
some intrinsic agonist to allow normal function
examples of partial agonists?
aripiprazole
buprenorphine
varenicline
what is an inverse agonist?
opposite effects to agonists
role of GABA in dementias and histamine in ADHD
what is meant by GABA subtypes?
neurotransmitter has 14 subtypes
receptor made of 5 different proteins
different locations for different receptor subtypes meaning they have different functions
comparison of dopamine blocker drug selectivity
haloperidol - very selective, adverse effects due to dopamine receptor block
clozapine - non selective, many adverse effects due to off targets (sedation, weight gain)
what is allosteric modulation?
drug acts on different sites of same protein complex e.g benzodiazapines and alcohol (GABA)
what is orthosteric binding?
drug binds to same site as endogenous neurotransmitter
comparison of serotonin reuptake blocker drug selectivity?
amitriptyline - TCA, less selective. also inhibits histamine and acetylcholine receptor
citalopram - SSRI, adverse effects driven solely by inc serotonin
