Mood disorders Flashcards
Give examples of 5HT2C antagonist properties
Antidepressant action
Disinhibition (enhancing) dopamine and norepinephrine release
Activating properties ( reduced fatigue, improved concentration. Therefore good for depressed patients with decreased positive affect.
Anti bulimia effect
List drugs with 5HT2C antagonism
- Fluoxetine
- Trazodone
- Mirtazepine
- Agomelatine
- Some tricyclic antidpressants
- Quietiapine & Olanzepine (5HT2A/ Dopamine 2 receptor antagonists)
What type of drug is Sertraline
SSRI with Dopamine transport (DAT) Inhibition and Sigma1 Binding
Sigma 1 actions with drug Sertaline
Anxiolytic effect in psychotic and delusional depression
Which drugs is Sertraline often combined with
Wellbutrin (bupropion), because both have weak DAT inhibitory properties
What type of drug is Paroxetine
SSRI with Muscarinic anticholinergic and norepinephrine transporter inhibitory actions
Why is Sertraline theoretically “activating”
It has Dopamine transporter inhibitory properties
Why is Paroxetine “calming/ sedating”
Because it has anticholinergic actions
Common side effect of paroxetine
Sexual dysfunction in men, due to Nitric oxide synthase enzyme inhibition
What type of drug is Fluvoxamine
SSRI with sigma 1 receptor binding
Pharmacological action of Fluvoxamine
Sigma 1 receptor agonist leading to a anxiolytic properties
What type of drug is citalopram
SSRI, which has 2 enantiomers (R&S),
Mild antihistamine properties come from the R entantiomer
Draw backs of Citalopram
Inconsistent therapeutic actions at low doses (often dose increases will be needed)
Limitations in dose increase (high doses lead to QT prolongation)
What type of drug is Escitalopram
SSRI
Why is escitalopram so well tolerated
Unwanted R enantiomer is removed (which removes antihistamine effects), no dosing restrictions (no risk for QT prolongation)
SSRI for which pure SERT inhibition most likely explains pharmacological effects.
Drug with fewest CYTP450 mediated drug interactions
What type of drug is Vilazodone?
Serotonin Partial agonist reuptake inhibitor (SPARI)
Which 3 actions do SNRI’s have|
- Increase serotonin
- Increase Norepinephrine
- Increase dopamine in the prefrontal cortex
Which transporter is found in small amounts in the prefrontal cortex
Dopamine transporter.
The consequence of the above is that when dopamine is released in the prefrontal cortex, it is free to cruise away from the synapse (this is known as having a wide diffusion radius). Therefore dopamine can have a widespread effect.
By which two mechanisms is dopamine inactivated in the prefrontal cortex.
Catechol o methyltransferase (degrades dopamine)
Uptake into the nerve terminal by NET (Norepinephrine transporter) - this reuptake stops the action of dopamine
Therefore when there is NET inhibition, there is an increase of norepinephrine and dopamine
What type of drug is Venlafaxine?
Venlafaxine is a Serotonin and Norepinephrine reuptake inhibitor (SNRI)
NET inhibition when Venlafaxine is given accounts for which 2 side effects?
- Sweating
- Elevated blood pressure
Why does Desvenlafaxine have more predictable NET inhibition over Venlafaxine?
There are genetic polymorphisms of CYP450 2D6, ie poor metabolisers which can shift the ratio of the 2 drugs more towards Venlafaxine (parent) and away from active metabolite Desvenlafaxine.
What type of drug is Duloxetine?
SNRI ( serotonin and norepinephrine reuptake inhibitor\0
Which conditions can be treated with Duloxetine?
- Unipolar depression
- Pain conditions without depression
- Painful symptoms associated with depression.
- Cognitive symptoms of depression in geriatric depression
Which pain syndromes have shown improvement on Duloxetine?
Diabetic peripheral Neuropathic pain
Fibromyalgia
Chronic MSK pain
Lower back pain
What type of drug is Milnacipran?
SNRI
Which pharmacological property make Milnacipran well suited for treating pain syndromes.
Milnacipran has more potent NET Inhibition than SERT inhibition.
* The potent NET inhibition makes it useful in pain syndromes
This property also makes it well suited for the treatment of cognitive symptoms ( cognitive symptoms of unipolar depression and cognitive symptoms associated with fibromyalgia).
Why may Levomilnacipran be favourable over Milnacipran
Once daily dosing instead of BD
(controlled release formulation )
What type of drug is Bupropion?
Norepinephrine-dopamine reuptake inhibitor.
Why does bupropion NOT cause sexual dysfunction?
Bupropion has limited serotonergic action.
When should Bupropion be used for unipolar depression:
- In patient’s who cannot tolerate serotonergic side effects of SSRI’s
- In patient’s who do not respond to serotonergic boosting
It is especially useful for dopamine deficient syndrome (patients lacking positive affect)
Which pharmacological properties does Agomelatine have?
- Agonist actions at Melatonin 1 and Melatonin 2 receptors
- Antagonist actions at 5HT2c
How does Agomelatine resynchronise circadian rhythms?
In the abscence of melatonin production from the Pineal gland, Agomelatin is able to act as a substitute melatonin and acts as an agonist on Melatonin 1 & 2 receptors In the suprachiasmic nucleus.
Additionally it also blocks 5HT2c receptors in the ventral tegmental area and locus coeruleus therefore promoting dopamine and norepinephrine release in the PFC.
Mirtazepine is a multifunctional drug, it has which 5 principal mechanisms of action?
5HT2a antagonism
5HT2c antagonism
5HT3 antagonism
alpha2 adrenergic antagonism
H1 histamine antagonism
h1 Antagonism causes
sedation and weight gain
5ht2A Antagonism causes:
Increase downstream release of dopamine in the prefrontal cortex.
Also improves slow wave sleep.
Alpha 2 antagonist actions ( as seen with Mirtazepine)
Alpha 2 autoreceptors on noradrenergic neurons are responsible for turning off norepinephrine release (auto receptor).
When this auto receptor is blocked, norepinephrine can no longer turn off its own release.
The same happens on alpha 2 heteroreceptors on the 5HT neuron
Where are 5HT3 receptors found in the body
Chemoreceptor trigger zone in the brainstem
(.where they mediate nausea and vomiting)
In the GI tract where they mediate nausea, vomiting and diarrhoea when stimulated by serotonin.
Therefore blocking 5HT3 receptors can protect against chemotherapy induced nausea and vomiting as well as serotonin induced Gi effects.
How does 5HT3 receptor antagonism ( Mirtazepine) have antidepressant effects.
5HT3 antagonism leads to disinhibition of glutamate release, and of acetylcholine and norepinephrine. These actions theoretically release neurotransmitters downstream to have antidepressant actions.
Which type of drug is trazodone?
Serotonin antagonist/ Reuptake inhibitor (SARI)
Which pharmacological actions does trazodone have (receptor)
5ht2a & 5ht2c receptor antagonism
5ht1d & 5ht7 receptor antagonism
alpha 1a, 1b, 2c, 2b antagonism
h1 receptor antagonism
5ht1A Agonism
Trazodone at low doses is used as a …
Hypnotic agent,
A hypnotic agent can potentially relieve insomnia and increase remission rates of depression. Remember the common residual symptoms of depression are often insomnia
How does trazodone exert its hypnotic effects
Blocking 5HT2a, alpha1 subtypes and H1
blocking 5ht2a receptors enhances slow wave sleep
blocking alpha1 and h1 receptors interferes with monoamine arousal mechanisms.
Vortioxetine is especially good at improving…?
Cognitive symptoms in unipolar depression
Name 4 domains of Cognition (fab four)
- Attention
2, executive function - Memory
- Processing speed
pharmacological actions of Vortioxetine
SERT inhibition and 5ht1a agonism
(raised serotonin levels- SERT inhibition, raised dopamine, acetylcholine and norepinephrine- 5ht1a agonism)
SERT inhibition and 5HT1b/d antagonism
stimulation of 5ht1b/d autoreceptors by serotonin turns off further serotonin release. Therefore antagonism of 5ht1b/d inhibits this negative feedback, allowing continuous release of serotonin.
5ht1b partial agonism/ antagonism causes downstream release of neurotransmitters ( DA, NE, HA, ACh)
5ht3 antagonism causes release of pro cognitive neurotransmitters.
5ht7 Antagonism: Serotonin inhibits its own release by 5HT7 receptors. Therefore antagonism of 5ht7 causes serotonin release.
How does postpartum depression happen
Pregnant women have high circling brain levels of naturally occurring allopregnanolone. After delivery there is a decline in brain levels of neuroactive substances triggering a depressive episode.
How does the drug Brexanolone (neuroactive steroid) work.
It rapidly restores neuroactive steroid levels over a 60 hour IV infusion. Rapidly reverses depression.
The 60 hour time also provides the necessary time for postpartum patients to accommodate to their lower levels of Neuroactive steroids without relapsing.
Neuroactive steroids bind to benzodiazepine sensitive and benzodiazepine insensitive GABAa receptors.
GABAa benzodiazepine insensitive receptors are thought to have antidepressant effects.
Treatment resistant unipolar depression:
Olanzepine- Fluoxetine option
5HT2a blocking properties of olanzepine likely account for anti depressive effects.
Both fluoxetine and Olanzepine have 5HT2c antagonist properties.
Therefore this combination of drugs can be thought of as a potent SERT/ 5HT2c inhibitor.
Unfortunately this combination often leads to unacceptable weight gain and metabolic disturbances.
Treatment resistant unipolar depression:
Quetiapine
Action in depression likely linked to combined actions of quetiapine and its active metabolite norquetiapine at both 5HT2c receptors and at norepinephrine transporters.
It also acts at other relevant receptors: 5HT2a, 5HT7, alpha2a and agonist at 5HT1a
Issues: sedation, moderate weight gain and metabolic disturbance.
Treatment resistant depression:
Aripiprazole
Antidepressive properties attributed to 5HT1a partial agonist actions
secondary properties: D3, 5HT7, 5HT2c, alpha2 antagonist actions.
well tolerated, little weight gain, some may experience akathisia.
How does brexpiprazole exert its antidepressant effects:
- Alpha1 receptor antagonism: This reduces glutamatergic output in the substantial nigra leading to reduced activity of the GABA interneuron and therefore disinhibition of the dopamanergic pathway (increasing dopamine)
*reduced dopamine in the motor striatum leads to reduction in Drug induced Parkinsonism. - Alpha1 receptor antagonism: reduces glutamateric output in the VTA leading to reduced activity in the GABA interneuron & therefore disinhibition (enhancing) mesocortical dopamine pathway.
- 5HT2A antagonism
How does Ketamine exert its antidepressant effects?
IV ketamine is a racemic mixture of R & S ketamine, each have binding properties at NMDA subtype of glutamate receptor, and at sigma1 receptor.
The leading hypothesised theory is that ketamine has NMDA antagonism specifically at the open channel phencyclidine site.
Why does ketamine cause immediate improvement in depression?
IV administration of ketamine has rapid onset antidepressant effects and antisuicidal ideation effects.
Ketamine causes immediate improvement in neuronal plasticity. Neurotropic factors such as BDNF (brain derived neurotropic factor ) and growth factors such as VEGF ( vascular endothelial growth factor) are deficient in chronic stress and major depression.
*Loss of BDNF and VEGF are linked to neuronal atrophy in the hippocampus and and prefrontal Cortex.
How does ketamine cause its rapid antidepressant effects?
Ketamine causes an immediate burst of downstream glutamate release after blocking the NMDA receptor.
Glutamate release stimulates AMPA receptors. These receptors active ERK, AKT signal transduction, which leads to expression of dendritic spines and synaptogenesis. Increase in dendritic spines and synaptogenesis is hypothesised to be the cause of rapid antidepressance.
What is Esketamine used for
It is an intranasal preparation of ketamine can be given weekly or twice weekly.
May be used as an augmenting agent to standard antidepressant drugs
What is California rocket fuel?
It is the combination of an SNRI and Mirtazepine:
Its action is achieved by combining the serotonin and norepinephrine inhibition of the SNRI with the disinhibition of serotonin and norepinephrine release by alpha2 antagonist actions of mirtazepine.
Mirtazepine also has pro dopaminergic actions by 5ht2c.
Antidepressant actions of tricyclic antidepressants
Block serotonin and norepinephrine.
Additionally some may have antagonist actions at 5HT2A and 5HT2C receptors.
Name 4 unwanted effects of tricyclic antidepressants
- Blockade of muscarinic cholinergic receptors
(dry mouth, blurred vision, urinary retention and constipation- anticholinergic effects) - H1 histamine receptors
(sedation and weight gain) - Alpha1 adrenergic receptors
(orthostatic hypotension and dizziness) - Voltage sensitive sodium channels.
(Blockage of sodium channels in the heart and the brain leading to seizures and arrhythmias)
How many subtypes of monoamineoxidase are there?
2, MAO A & B
List properties of MAO A
MAO A preferentialy metabolises the monoamines that are closely related to depression ( serotonin and norepinephrine)
MAO A also metabolises dopamine and tyramine
MAO A is found in the brain. MAO A is found in noradrenergic and dopaminergic neurons.
MAO A is the major form of enzyme found outside the brain.
Brain MOA A must be substantially inhibited for antidepressant effects to occur. This is because it is the enzyme primarily responsible for the breakdown of serotonin and norepinephrine which are 2 of the 3 monoamines linked to depression and antidepressant effects.
List properties of MAO B
Inhibition of MAO B is not effective as an antidepressant, because it has no effect on serotonin or norepinephrine metabolism.
When MAO B is selectively inhibited it can boost the action of concomitantly administered levodopa in Parkinson’s disease and reduce on/off motor fluctuations.
Name the 3 MAO B inhibitors approved for use in Parkinson’s
- Selegiline
- rasagiline
- safinamide
Precautions with MAOIs
- Tyramine containing foods are to be avoided. (cheese)
Tyramine releases norepinephrine which is usually destroyed by MOA A (tyramine ). In the presence of a MAOI, tyramine can elevate blood pressure because norepinephrine is not safely destroyed. - Drug drug interactions
avoid drugs that can raise BP by sympathomimetic action and those that can cause a potentially fatal serotonin syndrome by serotonin reuptake inhibition.
What similarities are there in Bipolar mania and Acute psychosis
Excessive dopamine levels and release in the mesostriatal dopamine neurons.
This explains why dopamine/ serotonin blockers work both in bipolar mania and acute psychosis
Which group of agents are used to treat bipolar depression and depression with mixed features, and which agents have fallen out of favour?
- Serotonin/dopamine blocking agents are used.
*The monoamine reuptake inhibitors are used less commonly now…
However, Olanzepine + Fluoxetine is still approved for the treatment of bipolar depression.
Which properties make the combination of Olanzepine and Fluoxetine a good combination for bipolar depression.
5HT2a and 5HT2c antagonism.
Properties that make Quetiapine good for bipolar depression.
5HT2A and 5HT2c antagonism
alpha2 antagonism
AGONIST actions at 5HT1a
D2 antagonist properties of quetiapine will prevent spill over into mania
What is cariprazines action:
D3/D2 & 5HT1a partial agonism
Which agent I the most potent for the D3 dopamine receptor
Cariprazine
Postsynaptic blocking of D3 receptors in the limbic region may lead to…
Antipsychotic effects
What happens when D3 is blocked in the ventral tegmental area?
The function of D3 receptors in the VTA, is to act as auto receptors; their function is to detect dopamine and inhibit further release.
Dopamine receptors in the prefrontal cortex are D1.
When D3 antagonists act in the VTA, this disinhibits the dopamine neurons projecting to the prefrontal cortex and they release dopamine onto D1 receptors..This theoretically has antidepressant effects.
Name 3 possible mechanisms of action of Valproic Acid
- Inhibiting voltage sensitive sodium channels
(Inhibits phosphorylation. Leading to less sodium being able to pass into the neuron which causes diminished release of glutamate and therefore less excitatory neurotransmission) - Boosting the actions of neurotransmitter GABA (therefore more inhibitory neurotransmission)
- Regulating downstream signal transduction
side effects of valproate
Sedation
weight gain
hairloss
Bone marrow
Liver
Pancreas
Neuro tube defects
Menstrual disturbances, Polycystic ovaries
Insulin resistence
Mechanism of action of Carbamazepine
Acts by blocking voltage sensitive sodium channels, within the channel itself; the alpha subunit of VSSC.