Pharmacology - antidepressants Flashcards
SSRIs mechanism of action
Increase serotonin activity by reducing the presynaptic reuptake of serotonin after release
Common side effects of SSRIs
Restlessness and agitation on initiation
Last for few weeks:
- Nausea and GI disturbance
- Headache
Long term:
- Weight changes
- Sexual dysfunction
- Bleeding
- Suicidal ideation - more energy but bleak outlook
Examples of SSRIs
Sertraline
Citalopram
Fluoxetine - give to under 25’s
Paroxetine
Cautions for specific SSRIs
Sertraline - safest in cardiac disease
Citalopram - Long QTc syndrome especially with antipsychotics
Fluoxetine - serotonin syndrome (long half-life)
Paroxetine - discontinuation syndrome (short half -life)
Use of SSRIs
Antidepressant used in depression and anxiety
SNRI method of action
Act in the same way as SSRIs plus binds to noradrenaline reuptake receptors as well
SNRI use
Neuropathic pain
SNRI side effects
Same as SSRIs but more likely to have sedation, nausea and sexual dysfunction
SNRI examples
Duloxetine - low dose
Venlafaxine - greater efficacy and can use higher doses
Venlafaxine cautions
Caution with heart disease
Monitor BP at higher doses
Mirtazapine mechanism of action
Acts of 5HT-2 and 5HT-3 antagonist
Strong histamine activity - sedation
Mirtazapine side effects
Sedation
Weight gain
TCA use
Low dose - neuropathic pain
High dose - second-line antidepressant if SSRI’s not tolerated
TCA side effects
Muscarinic side effects
Histaminic side effects
Long QTc syndrome and arrhythmias
Monoamine oxidase inhibitors types
MAOI A - serotonin receptors
MAOI B - dopamine receptors
Irreversible and reversible
Both can potentially increase adrenaline
Uses of MAOI
Used as an adjunct to increase the effectiveness of SSRIs
Effective for atypical depression
Examples of MAOI
Irreversible - more dangerous
- Phenelzine
- Isocarboxazid
Reversible - less dangerous
- Moclobamide
- Tranylcypromine
Side effects of MAOI
Tyramine reaction - hypertensive crisis
- avoid amino acids in cheese, pickled meats, wine
If changing to another antidepressant, needs a washout period of up to 6 weeks
Vortioxetine features
Serotonergic agonist and antagonist
- effective
- well-tolerated
- used to treat cognitive symptoms
Monitoring on antidepressants
Measure weight before antidepressants
Anti muscarinic side effects
Dry Mouth Palpitations Difficulty swallowing Thirst Urinary retention Hot and flushed skin Dry skin
Histamine side effects
Dry mouth
Drowsiness
Dizziness
Nausea and vomiting
Discontinuation syndrome
Antidepressants are not addictive but there can be withdrawal symptoms
- sweating
- agitation and tremor
- insomnia
- headaches
- nausea and vomiting
- clonus
- paraesthesia
- increased mood change
Shorter half-life, bigger problem
How to minimise discontinuation syndrome
- Alternate days of taking and not taking
- Take half tablets
- Can switch from paroxetine to fluoxetine before reducing
Serotonin syndrome features
Cognitive - headaches, agitation, hypomania, confusion, coma
Autonomic - shivering, sweating, hyperthermia, tachycardia, nausea and diarrhoea
Somatic - myoclonus, hyper-reflexia and tremor
Treatment of serotonin syndrome
Fluids and monitoring
Cause of serotonin syndrome
SSRI + MAOIs
How to prevent serotonin syndrome
Give a 14 day SSRI washout period before starting MAOIs
Antidepressant interactions
NSAIDs - increased risk of bleeding
Other antidepressants - serotonin syndrome
Carbamazepine, diuretics - hyponatraemia
How to withdraw from antidepressants
Withdraw slowly for at least 4 weeks to reduce the severity of discontinuation syndrome
