Depression - Treatment Flashcards
How do the MAOIs result in therapeutic effects?
Inhibit monoamine oxidase to increase biological availability of monoamines – counteract deficits in monoamine neurotransmitters
- MAO-A: noradrenaline, dopamine, 5-HT (Serotonin)
- MAO-B: noradrenaline and dopamine only
(moclobemide - reversible antagonism)
What are the adverse effects of MAOIs
- Postural hypotension – likely due to sympathetic block produced by accumulation of dopamine in the cervical (neck) ganglia, where it acts as an inhibitory transmitter
- Restlessness and insomnia – due to CNS stimulation
- Should not be combined with other drugs enhancing serotonergic function (e.g. pethidine) – can result in hyperexcitability, inc muscle tone, myoclonus (jerking, involuntary movements), loss of consciousness
How does the interaction between MAOIs and cheese work?
- Amines (e.g. tyramine) in foods are usually broken down by MAO in the intestines and liver
- Inhibition of MAO allows them to exert sympathomimetic effect – tyramine gets taken into adrenergic terminals , competes w NA for vesicular compartment, ↑NA release to synapses
- Less likely with reversible MAO-A selective MAOIs (e.g. moclobemide)
What is the MOA of the TCAs?
Blocks reuptake of NA and 5-HT
Non-selective for Serotonin and Norepinephrine Transporters: Imipramine, Amitriptyline, Nortriptyline
Selective for Norepinephrine Transporter: Desipramine
What are the adverse effects of the TCAs?
Sedation – due to H1 histamine receptor antagonism
* Tolerance to sedation can develop in 1-2 weeks
Postural Hypotension – due to α-adrenoreceptor sympathetic block
Dry mouth, blurred vision, constipation – due to muscarinic receptor antagonism
What are the advantages of SSRIs?
- Low affinity for α-adrenoreceptors – lack of CV effects, safer in overdose
- Lack of effect at histamine receptors – reduced sedation
- Low affinity for muscarinic cholinergic receptors – minimal anticholinergic SE
- Due to less side effects, able to prescribe more adequate doses (compared to TCAs that are frequently used at subtherapeutic doses due to intolerability of adverse effects)
What is the MOA of SSRIs?
Selectively blocks reuptake of 5-HT
What are the adverse effects of SSRIs?
→ Nausea
→ Insomnia
→ Sexual dysfunction
→ Citalopram still has some histamine receptor antagonism leading to sedation
→ Serotonin Syndrome – DDI with other drugs increasing serotoninergic activity
(Tremor, Hyperthermia, Cardiovascular collapse)
What is the MOA of SNRIs?
Blocks reuptake of NA and 5-HT
What are the adverse effects of SNRIs?
→ Serotoninergic adverse effects similar to SSRIs: nausea, insomnia, sexual dysfunction
→ Serotonin syndrome when combined with other serotoninergic drugs
→ Withdrawal effects may be more common and stronger than for SSRIs and TCAs
What is the MOA of mirtazapine?
→ Norepinephrine and specific serotonin antidepressant
→ Antagonist of adrenergic α2 autoreceptors and 5-HT2C receptors, among others
What is the MOA of bupropion?
Blocks reuptake of NA and DA
What is the MOA of agomelatine?
MT-1, MT-2 agonist
5-HT2C antagonist
↑DA and NA
What is the MOA of ketamine?
Glutamate NMDA agonist used as anaesthetic, currently evaluated for rapid onset antidepressant effect
What is the MOA of vortioxetine?
Multimodal serotonergic antidepressant – novel class
* Agonist activity at 5-HT1A receptor
* Partial agonist activity at the 5-HT1B receptor
* Antagonism at 5-HT1D, 5-HT7, and 5-HT3 receptors
Additional receptor affinities may ↑release of serotonin and release other neurotransmitters
May be efficacious in patients resistant to other antidepressants
May also have pro-cognitive effects