Antidepressants Flashcards
Important early evidence for Monoamine theory came from the observation that reserpine, which inhibits ___ and ____ storage, depressed mood.
NA (noradrenaline)
5-HT (serotonin)
Initially, the monoamine theory was formulated for ____, but the emphasis for Monoamine theory has since shifted towards _____.
- NA
2. 5-HT
Where is Monoamine oxidase (MAO) found in the human body?
Found in nearly all tissues, including nerve terminals, intestine, and liver.
Found intracellularly, mostly on the mitochondrial surface
There are 2 major forms of MAO.
Neurochemical _____ is mainly broken down by MAO-A.
5-HT
Which MAO form acts on NA and dopamine?
Both forms of MAO act on NA and dopamine and have equal selectivity.
MAO-B selective inhibitors (i.e. selegiline) are used in _________.
Parkinson’s disease
Which part of the synapse is MAO found at the synaptic junction?
Pre-synapse (intraceullarly)
Effect of MAO-inhibitors on monoamines?
Increased biological availability of monoamines.
Phenelzine is more/less/non selective for MAO-A vs MAO-B.
Non-selective
Phenelzine is more/less/non selective for MAO-A vs MAO-B.
Non-selective
What are the adverse effects of MAO inhibitors?
- Postural Hypotension
2. Restlessness and insomnia
MAOIs can cause Postural Hypotension via ________ caused by accumulation of dopamine in cervical (neck) ganglia, where it acts as an ______ transmitter.
- sympathetic block
- inhibitory
(heart can no longer pump faster in response to postural change = insufficient blood to brain)
MAOIs can cause restlessness and insomnia due to _____ stimulation.
CNS
Why should MAOIs not be combined with drugs that enhance serotoninergic function, such as Pethidine?
May lead to: Hyperexcitability, increased muscular tone, myoclonus (jerking, involuntary movements), loss of consciousness
What is the interaction in the ‘Cheese’ reaction and what is it caused by?
A Drug-Food interaction arising from consuming cheeses and concentrated yeast products (i.e. marmite) together with MAOIs
What are the consequences of a ‘Cheese reaction’?
Acute hypertension, giving severe throbbing headache, and occasionally intracranial haemorrhage
How can we try to prevent ‘cheese’ reaction?
- Avoid taking Cheese/conc. yeast food with MAOI
2. Use reversible MAO-A/B selective inhibitors (i.e. moclobemide)
‘Cheese’ reaction is _____ likely to occur with reversible, MAO-A/MAO-B selective(e.g. moclobemide) vs. irreversible, non-selective MAOIs
less
non selective = more enzymes blocked = worse reaction
What is the MOA of the cheese reaction?
- Amines such as tyramine (in cheese) accumulate when MAOs are inhibited.
- Tyramine is taken up into adrenergic terminals and competes with NA for vesicular compartment.
- Increased NA release into synapses. (sympathomimetic effect)
What is the MOA of the cheese reaction?
- Amines such as tyramine (in cheese) accumulate when MAOs are inhibited.
- Tyramine competes with NA for vesicular compartment.
- Increased NA release into synapses and a sympathomimetic effect.
_________ are TCAs that are non-selective for SERT/NET.
Imipramine, Amitriptyline, nortriptyline
________ is a TCA that is selective for NET.
Desipramine
Nortriptyline is a _______ TCA that has _______ compared to amitriptyline and imipramine which leads to _______________.
- 2nd gen TCA
- milder side effects
- improved compliance
Nortriptyline is a _______ TCA that has _______ compared to amitriptyline and imipramine and improved compliance.
- 2nd gen TCA
2. milder side effects
TCAs can lead to sedation due to ________ receptor antagonism. Tolerance to sedation can develop in ____ weeks
- H1 Histamine
2. 1-2wks