Tricyclic and related antidepressants & MAOIs Flashcards
Mechanism of action
Block re-uptake of both serotonin and noradrenaline - although to different extents
What adverse effects in overdose vary between the different types of these class of drugs?
Antimuscarinic effects
Cardiotoxicity
How can this class of drugs be easily divided?
Between those with a sedative effect (e.g. amitriptyline) and those with a less sedative effect (e.g. nortriptyline)
Why is amitriptyline no longer recommended in the treatment of depression?
It is very dangerous in overdose
Why do some patients fail to respond to tricyclics?
Inadequate dosage
Therapeutic dose needs to be high but if dose is too high it becomes toxic
Why is it that tricyclics are often only needed to be administered once a day?
Long half life
When is it best to take tricyclics?
At night
What conditions other than depression are some tricyclics used to treat?
Neuralgia
Nocturnal enuresis - bedwetting (children)
What are some common tricyclics?
Amitriptyline Hydrochloride
Dosulepin Hydrochloride
Which patients are said to respond well to MAOIs?
Phobic patients with atypical hypochondrial or hysterical features
Why are MAOIs rarely prescribed?
Due to dietary and drug interactions
What is Monoamine oxidase?
An enzyme which destroys Norepinepherine (noradrenaline)
Where does the name Tricyclic originate from?
The three ring chemical structure of the drugs
Foods containing what can lead to a hypertensive crisis if consumed with MAOIs?
Tyramine
What is Tyramine?
A form of the amino acid Tyrosine
Why is it dangerous to consume foods with Tyramine whilst taking MAOIs?
MAO breaks down Tyramine. MAOIs therefore inhibit the breakdown of tyramine leading to high concentrations entering the blood stream. It displaces norepinephrine within presynaptic nerve terminals causing a sudden release of norepinephrine causing acute hypertension.
What can be given as an antidote to a MAOIs hypertensive crises caused by eating foods with tyramine?
Calcium Channel blockers.
