Antidepressants Flashcards
What is the common aim of antidepressants?
work on serotonin activity and aim to increase activity in post synaptic receptors
*most effective in 2-3w and clinically detectable in 4-6w
What is the mechanism of action of SSRI?
reduce presynaptic reuptake of serotonin after release, serotonin sits in synapse, down regulation of post synaptic receptors
What are some side effects of SSRI?
GI: nausea, diarrhoea, constipation
sweating, tremor
headache
weight changes
sexual dysfunction
bleeding and suicide ideation (from more motivation as a result of meds) less common
What is something to be aware of when monitoring SSRI?
be wary of those with exaggerated response to meds, as may induce mania!!
What are some SSRI examples?
sertraline (safest in cardiac disease)
citalopram
fluoxetine
paroxetine
What is serotonin syndrome?
rare but life threatening complication of increased serotonin, rapidly within minutes
- cognitive: headache, agitation, hallucination, coma,?seizure
- autonomic: shivering, sweating, hyperthermia, tacky
- somatic: myoclonus, hyperreflexia, tremor
*stop offending drugs and give supportive measures
How does serotonin and noradrenaline reuptake inhibitors work?
same as SSRI but on noradrenaline reuptake receptors too! no cholinergic block
eg: duloxetine and venlafaxine
What are some side effects of SNRI?
similar to SSRI
more sedation potential, nausea, sexual dysfunction
What is the mechanism of action of Mirtazapine?
*used to be called noradrenergic and specific serotonergic antidepressant
weak NA reuptake inhibitor, strong anti-histaminergic properties, alpha 1 and 2 blocker!
What are some side effects of Mirtazapine?
increased appetite
weight gain
sedation
What is the mechanism of action of TCA?
inhibiting serotonin and adrenaline reuptake in synaptic cleft
affinity for cholinergic and 5HT2 (dopamine related)
eg: amitriptyline, clomipramine, imipramine
*low doses for neuropathic pain
What are some side effects of TCAs?
anticholinergics: dry mouth, constipation, urinary retention
QTc prolongation and arrhythmia risk
What is the mechanism of action of Monoamine oxidase inhibitors?
inactivate the enzymes that is involved in the removal of NA, serotonin and dopamine. type A more on serotonin and B on dopamine. both potentially adrenaline.
*mostly effective for atypical depression
eg: irreversible - phenelzine
reversible - moclobemide
What are some cautions with MAOI to know about?
dangerous interactions with other drugs
tyramine reaction (MOAI also metabolises tyramine) potential leading to hypertensive crisis –> avoid cheese, pickled meat, wine etc
*headache, palpitations, fever
if changing to other need washout period of unto 6w
How to know which antidepressant to use?
- what has been used before
- was it effective or tolerated?
- comorbidities: WL, insomnia, neuropathic pain
- side effects
- pt expectation: ‘use placebo to your advantage’
*SSRI unless major weight loss or sleep difficulty (Mirtzapine better) or elderly with falls risk
*neuropathic pain consider SNRI
*SSRI first mostly then to different SSRI then to SNRI Venlafaxine or Mirtazapine
