Chapter 4 - Central Nervous System Flashcards
What are the three main classes of antidepressants?
- Tricyclic antidepressants (TCAs)
- Monoamine oxidase inhibitors (MAOIs)
- Selective serotonin re-uptake inhibitors (SSRIs)
How long is it thought to take for an antidepressant to exert its therapeutic effect?
2 weeks
Which two criteria are used in the diagnosis of depression?
ICD-10 (international classification of diseases)
DSM-4 (Diagnostic and statistical manual of mental disorders) NICE guidelines uses this diagnostic criteria
Depression can be caused by psychological, genetic and biological factors. What are the likely ‘biological candidates’ which have shown to play a part in depression?
Cortisol and Monoamines
monoamine hypothesis proposes a functional deficit of monoamine transmission in
the central nervous system, involving deficits of the neurotransmitters noradrenaline, serotonin (5-HT) and dopamine in the synaptic cleft.
Depression is thought to cause higher cortisol levels
Which drugs may contribute to ‘drug induced depression’?
Isotretinoin
Montelukast
Systemic corticosteroids
Levodopa
What important counselling point should you give to patients starting mirtazepine?
Mirtazepine may cause blood disorders - patients are advised to report any sore throat, fever or other signs of infections
What role do benzodiazepines have in the treatment of mania?
Useful in the initial stages of treatment for behavioural disturbance or agitation. Long periods aren’t used because of the risk of dependence
What treatment options are available for the long term treatment of bipolar disease?
Antipsychotics (e.g olanzapine)
Lithium
Valproate or Lamotrigine
Which antipsychotic drugs are generally used in the treatment of acute episodes of mania?
Olazanpine, quetiapine and risperidone
How long does it generally take for the full prophylactic effect of lithium to occur for the treatment of bipolar disease?
6-12 months
What major side effects are associated with lithium use?
- Hypo or hyperthyroidism- lithium increases intrathyroidal iodine content, inhibits the coupling of iodotyrosine residues to form iodothyronines (thyroxine [T4] and triiodothyronine [T3]), and inhibits release of T4 and T3
- renal dysfunction
- lithium toxicity
When should samples be taken to check lithium levels?
12 hours after the dose, 7 days after initiation
What should optimum serum lithium levels be?
0.4-1mmol/L
What specific advice should patients/carers be given for someone initiated on lithium?
Report signs/symptoms of:
- lithium toxicity
- hypothyroidism
- renal dysfunction (polyuria, polydipsia (excessive thirst))
- benign intercranial hypertension (persistent headache, visual disturbances)
Attend all routine blood tests
Can different preparations of lithium be used interchangeably?
No, preparations vary in bioavailability. Changing preparations requires the same precautions as initiation of treatment
Which antidepressant is safe to be used in a patient who has unstable angina or had a recent myocardial infarction?
Sertraline
Which class is the most ‘efficacious’ antidepressant?
None, all have similar efficacy to each other. The side-effect profile and patient factors determines choice.
Which electrolyte imbalance is commonly associated with antidepressant use?
Hyponatraemia - particularly with SSRIs
What is the MOA of TCAs?
Block the re-uptake of serotonin and noadrenaline by blocking the re-uptake channels. They als adversely block muscarinc and histamine receptors which accounts for their increased side effect profile in comparison to SSRIs.
TCAs can be roughly dicided into sedating and less sedating properties. Which TCAs have sedative properties?
Amitriptyline Clomipramine Dosulepin Doxepin Mianserin Trimipramine
Which TCAs are less sedative?
Imipramine
Lofepramine
Nortriptyline
Which two TCAs are NOT recommended for the treatment of depression?
Amitriptyline and dosulepin - particularly dangerous in overdose
Which TCA has more marked antimuscarinic effects?
Imipramine
Which TCA is less dangerous in overdose and has a lower incidence of side effects?
Lofepramine
True or False: TCAs have a long half-life
True - which is why it allows for once daily administration usually given at night
Are tricyclics effective in treating depression in children?
Studies have shown that they aren’t effective in treating depression in children
Why are MAOIs not generally used unless started under a specialist for the treatment of depression?
Have dangerous drug and food interactions
What is the MOA of MAOIs?
Block the monoamine oxidase enzyme which functions to breakdown serotonin and noradrenaline when they have been re-uptaken back into the Pre-synaptic neurones to be repackaged.
There are two subtypes of Monoamine oxidases
Which drugs belong to the MAOIs?
Phenelzine
Tranylcypromine
Isocarboxazid
Moclobemide
Citalopram and Escitalopram are contra-indicated in patients with what?
QT-interval prolongation - both can cause QT-prolongation as a side-effect