Pharmacodynamics Flashcards
Which psychiatric drugs affect the storage of neurotransmitters?
Reserpine depletes NA and DA
Which psychiatric drugs cause partial agonism?
Aripiprazole - D2
Buspirone - 5HT1A
Clonazepam - BDZ receptor
Buprenorphine - opioid receptor mu
Which receptor does Buprenorphine cause partial agonism at?
Opioid receptor mu
Which psychiatric drugs cause full agonism?
Benzos - GABA-A complex
Bromocriptine - dopamine
E.g. of ionotropic receptors?
Acetylcholine
GABA-A
Glutamate
5HT-3
Examples of Metabotropic receptors?
Dopamine - D1-5 Noradrenaline 5HT1-7 (except 5HT-3) Muscarinic Acetylcholine receptors Opioid receptors - mu
What is a ceiling effect?
Related to partial agonists; degree of response depends on availability of physiological neurotransmitter in the vicinity.
What is competitive antagonist?
Can be reversed by increasing dose of agonist drug.
Reduce potency but not efficacy of agonist.
What is potency?
Minimal dose needed to produce an efficacy
How do noncompetitive antagonists work?
Alter receptor site so increasing dose of agonist drug can reverse effects on partially.
Reduces both potency and efficacy of agonists.
Shift curve to right.
E.g. of noncompetitive antagonists.
Ketamine and phencyclidine are noncompetitive NMDA antagonists.
What is pharmacological antagonism?
Opposing action of 2 molecules acting via same receptor
What is physiological antagonism?
Opposing action of 2 molecules by acting via different receptors
What is the potency of a drug?
Amount of drug needed to produce particular effect compared to another standard drug with similar receptor profile (vigor)
What does efficacy depend upon?
Affinity
Potency
Duration of receptor action
Kinetic properties such as half-life
Mechanism of Amisulpride?
D2 and D3 antagonism
Dose-dependent
Limbic selectivity an 5HT7 activity
Mechanism of Aripiprazole?
Partial dopamine agonist at D2
5HT2A antagonist
Mechanism of Asenapine
D2 antagonist and 5HT2A blocker
Alpha-2 blockage
Mechanism of clozapine?
High ratio of 5HT2 to D2 blockade Blocks D4 and 5HT5 Alpha 1 antagonism Anticholinergic and antihistaminic properties Weak D1 and D2 affinity Binds 5HT3
Mechanism of Lurasidone?
D2 antagonist 5HT2A blocker High affinity for 5HT7 Partial agonist at 5HT1A receptors Minimal affinity for alpha-1 (less orthostatic effect) and histamine receptors (perhaps weight neutral)
Mechanism of Olanzapine
High 5HT2/D2 blockade ratio.
Potent D4 blockade and 5HT6 blockade
Significant anticholinergic and antihistaminic effects
Mechanism of Risperidone
Serotonin-Dopamine antagonist.
High 5HT2A antagonist.
Therapeutic doses: binds D2 similar to typicals -> EPSEs and prolactin SEs
Mechanism of Sulpride?
Pure D2 antagonist.
Low doses: presynaptic receptors blocked (helps with -ve symptoms).
Above 800mg/day; affects postsynaptic D2 - reducing +ve symptoms.
Mechanism of Zotepine
Atypical antipsychotic 5HT2A, 5HT2C, D1-D4 antagonism Potent noradrenaline reuptake inhibitor Potent antihistaminic activity Some NMDA antagonism
Mechanism of action of Agomelatine as an antidepressant
Enhances norepinephrine and dopamine neurotransmission through 5-HT2C antagonism.
Norepinephrine and dopamine disinhibitor via 5HT2C inhibition
How does Agomelatine cause inhibition of norepinephrine and dopamine via 5HT2C
GABA interneurons tonically inhibit noradrenergic circuits from locus coeruleus and dopaminergic ciriuts from ventral tegmentum, projecting to prefrontal cortex.
Serotonin via 5HT2C stimulation drives these GABA interneurons.
Structure of Amoxapine
Tetracyclic with dibenzoxazepine structure
Mechanism of Amoxapine
Both dopamine antagonistic and serotonin-noradrenaline reuptake inhibition effects.
Antipsychotic + antidepressant.
EPSEs.
Mechanism of Buspirone?
Partial agonist on 5HT1A
Presynaptic - full agonist, inhibits release of serotonin which leads to antianxiety.
Postsynaptic - partial agonist to account for antidepressant activity.
Mechanism of Desipramine
Tricyclic with least anticholinergic action but lethal on OD.
Mechanism of Milnacipran
SNRI
Mechanism of Mirtazapine
5HT2A antagonism
Alpha 2 antagonism
Antihistaminic
Anti 5HT3
Mechanism of Moclobemide
Reversible inhibitor of MAO-A electively.
Mechanism of Nefazadone
5HT2A antagonist with serotonin ruptake inhibition and mild norepinephrine reuptake inhibition.
Alpha 1 antagonism
Mechanism of Pindolol
Beta blocker with intrinsic symapthomimetic activity.
5HT1A antagonism - possibly enhances action of SSRI by this
Mechanism of action of Selegiline
MAOI - selective for B at normal dose.
Selectivity lost when applied at higher doses
Mechanism of action of Tranylcypromine
MAOI - irreversible, non-selective.
Mechanism of Vilazodone
Selective serotonin reuptake inhibition
Partial agonist at 5HT1A
Mechanism of Vortioxetine
SSRI-like effect
5HT3 antagonism
5HT1-A agonism
Mechanism of Carbamazepine
Prolongs Na channel inactivation, so that ca channel inactivation is prolonged.
Reduces glutamate neurotransmission,
Mechanism of Lamotrigine
Neuronal stabilization
Block Na channel–>decrease glutamate release
Mechanism of Levetiracetam
Indirectly enhances GABA system
Mechanism of Tiagabine
Potent and selective reuptake inhibitor of GABA.
Mechanism of Topiramate
Enhances GABA
Blocks glutamate at NMDA
Mechanism of Valproic acid
Enhances GABA
Inhibits GABA aminotransferase
Increases GABA binding sites
Mechanism of Benzos
Act via omega site in GABA-A all agonists (except clonazepam - partial)
Mechanism of Ramelteon
MT1 and MT2 agonist with high affinity
Decreases sleep latency, increases sleep time.
Mechanism of alcohol
Intercalates into fluid cell membrane
Decreases NMDA sensitivity
Increases GABA sensitivity
Mechanism of amphetamine
Acts via releasing stored monoamines - noradrenaline and dopamine.
Mechanism of clonidine and lofexidine
Presynaptic alpha 2 agonist - reduces central sympathetic tone.
Mechanism of disulfiram
Inhibits aldehyde dehydrogenase
Leads to accumulation of acetaldehyde if alcohol is consumed.
Mechanism of LSD
5HT2A partial agonism - produces hallucinogenic effect
Mechanism of methadone
Opioid receptor agonist
Longer acting than heroin
Pure mu agonist
Mechanism of varenicline
Alpha 4 beta 2 partial agonist
Rivastigmine
Rivastigmine inhibits both acetyl and butyl-cholinesterase.
Galantamine
Galantamine - nicotine agonist
Which drug is approved for use in MND?
Riluzole
What does Riluzole do for MND?
Prolongs survival by 10% for more than a year of treatment
Riluzole’s mechanism of action?
Na channel blockade
High voltage Ca channel blockade
NMDA glutamate receptor antagonism
Mechanism of dextroamphetamine and methylphenidate
induce release of dopamine and noradrenaline from presynaptic neurons.
Weak inhibitors of catecholamine reuptake
Mechanism of atomoxetine
Selective inhibitor of presynaptic noradrenaline reuptake
Cyproheptadine -
antihistamine and 5HT2 antagonist.
What was Cyproheptadine used as?
Treat delayed ejaculation associated with SSRI use
Mechanism of Modafinil
Activates hypocretin-producing neurons through alpha 2 and alpha 1 adrenergic agonist properties and noradrenaline reuptake blocking effects.
Mechanism of pramipexole, ropinirole, aopmorphine
Dopamine agonists - bind 20x more selectively to D3 than D2.
Pramipexole - nonergot dopamine agonis
Mechanism of sumatriptan
5HT1D and 1F agonist
Mechanism of yohimbe
Alpha 2 antagonist
Used to treat erectile dysfunction
Relationship between ECT and kindling?
ECT is anti-kindling
How does ECT lead to neurogenesis?
Mediated by increased expression of brain-derived neurotrophic factor and its receptor
What happens to blood brain barrier permeability in ECT?
Acutely increases, returns to normal within 24 hours
EEG activity in ECT
Delta and theta activity afterwards - returns to normal after 3 months
Impact of ECT on neurotrophic factors
Increase in NGF, BDNF, NF3
Impact of ECT on hormones
Increased cortisol, prolactin and TSH coincides with good response.
Impact of ECT on 5HT2 receptors?
Increase
Which ethnicity are poor metabolizers of CYP2D6?
Caucasians - 7%
East asians - 1%
These lack this enzyme so are poor metabolizers of TCAs and risperidone
Etnicity with intermediate metabolization of CYP2D6?
Higher in asians - higher SE but good drug efficacy
Which ethnicity are ultrarapid metabolizers of CYP 2D6?
33% of north africans - they have multiple copies of CYP 2D6
5% cauccasians
1% east asians
25% indians
weight gain caused by antipsychotics
5HT2C block
GI side effects caused by SSRIs
5HT3 stimulation
Newborn with spina bifida
Valproate
What should ideally not administered with Fluvoxamine
Diazepam
Theophylline
Warfarin
Acidification of urine helps eliminate what drugs
Amphetamine
PCP
OD with amitryptiline
Diazepam to prevent seizures
treatment for excessive salivation with clozapine
Hyoscine 300micrograms
Therapeutic blood level for clozapine
350-500 micrograms/L
Therapeutic blood level for amitrtriptyline
100-200 micrograms/L
Mechanism of atomoxetine
Inhibits NE transporter
Treatment of NMS
Dantrolene
Bromocriptine
what is a heteroreceptor
A receptor that mediates the synthesis of mediators other than its own ligabd
Blockade of postsynaptic alpha-1 Receptor
Orthostatic hypotension
Sedation
Tolerance to LSD
downregulation of 5HT2
Clozapine induced hypersalivation
M4 agonism
Low incidence of EPSE
5HT2 blockade
Mechanism of vigabatrin
irreversibly inhibits GABA transaminae
Side effect of reboxetine in 10% males
Urinary hesitency
Hydralazine MAOi
Phenelzine
isocarboxizid
Non-hydralazine MAOi
Tranycypromine
Mechanism of dry mouth TCAs
M3 antagonism
Most important side effect with anti- dementia drugs
Bradycardia
Competitive antagonist
reversed completely by increasing dose of agonist
Reduce potency but not efficacy
Mechanism of GHB
GABA-B agonist
1/2 life of temazepam
10 hours