Antidepressants Flashcards
What are the examples of SSRI’s?
- Citalopram (most selective)
- Fluoxetine
- Paroxetine (most potent)
- Sertaline
What is the mechanism of action
- Limits the reabsorption of serotonin in the presynaptic cell
- This increases the level of serotonin in the synaptic cleft available to bind to the post synaptic receptor and carry on action potential
What are the side effects of SSRI’s?
- Nausea
- Sexual dysfunction
- Insomnia
- Anorexia
- Diarrhoea
- Prolonged QTc interval
- Precipitation in mania, possible suicidal ideation, tremor (rare)
What causes serotonin syndrome?
- Due to excess serotonergic neurotransmission
- Occurs within a few weeks of initiating SSRIs or when more than 2 used at once commonly
- Confused with the neuroepileptic malignant syndrome
What are the symptoms of serotonin syndrome?
- Tachycardia
- Sweating
- Dilated pupils
- Myoclonic
- Hyperthermia (causes complications)
- Seizures
- Muscle breakdown
Which drugs are used for depression?
- Serotonin Selective Reuptake Inhibitor (SSRI)
- Tricyclic Antidepressants (TCA)
- Serotonin/Noradrenergic Reuptake Inhibitor (SNRI)
What are the pharmacokinetics of SSRIs?
- Almost completely absorbed from gut
- Long elimination half lives
- Metabolised in the liver
- Reasonably safe in overdose
When is amitriptyline indicated?
- Depression
- Diabetes
- Pain
What are the examples of TCAs?
- Amitriptyline
- Duloxetine
- Clomipramine
- Lofepramine
Used less often
What is the mechanism of action of TCA?
Act largely as SNRIs
- Inhibition of noradrenaline uptake resulting in enhanced noradrenergic neurotransmission
- Muscurinic Cholinoceptor blockage so reduced chlinergic neurotransmission
- Alpha 1 adrenoceptor blockage so suppression of noradrenergic neurotransmission
What are side effects of TCAs?
- Dry mouth
- Dry nose due to reduction in glandular secretions
- Blurry vision due to lack of eye accommodation block
- Constipation (lowered gastrointestinal motility)
- Urinary retention
- CNS - sedation and impairment of psychomotor performance, lowering of seizure threshold
- Increased body temperature.
- CVS - tachycardia, postural hypotension, impaired myocardial contractiity
What are some toxicities demostated by TCAs?
- CARDIOTOXIC: can result in life threatening inhibitors
- NEUROTOXIC: seizures, hallucinations, delirium and coma
When are TCAs contraidicated?
-Do not prescribe if suicidal as overdose is lethal
What the pharmacokinetics of TCAs?
- Lipid soluble
- Absorbed from gut
- Long half lives
- Metabolised in liver
What are examples of SNRI’s?
- Venlafaxine
- Duloxetine
Which drugs are given first, second and thirdline for (moderate - severe) depression?
- SSRIs
- TCA/SNRI
- TCA/SNRI
What is the mechanism of action of SNRI?
- Inhibition of noradrenaline uptake, resulting in enhanced noradrenergic neurotransmission
- Muscarinic cholinoceptor blockade so reduced cholinergic neurotransmission (anticholinergic effect)
- Alpha 1 adrenoceptor blockage so suppression of noradrenergic neurotransmission
What are the side effects of SNRIs?
- Sleep disturbance
- Increased blood pressure
- Dry mouth
- Hyponatraemia
- Relatively short half-life therefore may be withdrawal syndrome on discontinuation
- Nausea
- Sexual dysfunction
- Insomnia
- Anorexia
- Diarrhoea
- Prolonged QTc interval
- Precipitation in mania, possible suicidal ideation, tremor (rare)
Which drugs are used for anxiety?
- SSRIs
- TCA
- SNRIs
How does the action of SNRIs change depending on the dose?
- High doses have more noradrenaline action
- Lower doses have more serotonin action
Are MAOI’s used in practice for depression?
No
