Monoamine Oxidase Inhibitors Flashcards
(21 cards)
What are common examples of monoamine oxidase inhibitors?
moclobemide and phenelzine
What is the mode of action of moclobemide?
Reversible inhibitor of MAO-A and MAO-B
What is the mode of action of phenelzine?
Form stable complexes with the enzyme causing an irreversible inactivation of MAO-A and MAO-B
What is the major side effect of MAO inhibitors?
“Cheese reaction” or hypertensive crisis caused by irreversible inhibition of MAO-A in the gut and liver
which prevents breakdown of dietary tyramine.
What are the other side effects of MAO inhibitors?
-Potentiates the effects of other drugs (barbiturates) by decreasing their metabolism -insomnia (stimulant) -Postural hypotension -Peripheral oedema
What is a “cheese reaction”
When a large amount of tyramine is consumed, a
tyramine pressor response occurs in which there is an increase of systolic pressure of 30mmHg or more
Are antidepressants useful in general?
Yes, there is clear evidence that it is more useful in
severe depression. More of a placebo effect is seen
in those with mild depression.
What is Monoamine Oxidase?
It is a mitochondrial enzyme in nerves (as well as gut & liver) which functions as safety valve to inactivate any excess neurotransmitter (Norepinephrine, dopamine, sertononin)
Why are the use of MAO-I restricted?
Because of the complicated dietary restrictions required when taking these medications
What are the indications of MAO-I?
For patients with depression who are unresponsive to TCAs and SSRI’s or who experience strong anxiety or atypical depression (mood brightens to positive events)
How long does it take for MAO to regenerate
2 weeks. When switching MAO-I to another class of antidepressants, 2 weeks of delay must be allowed.
How are MAO-I metabolised
In the liver and excreted in the urine
How does MAO-I cause a “cheese reaction” or hypertensive crisis?
Undegraded tyramine causes large amounts of catecholamines from nerve terminals. Norepinerphrine is usually broken down by MAO-A so its inhibition leads to accumulation of NE leading to a hypertensive crisis
What are the signs and symptoms of a hypertensive crisis?
- occipital headache
- stiff neck
- tachycardia
- hypertension
- cardiac arrhythmia
- seizures
- stroke
Can MAO-I’s be prescribed with other antidepressants
NO! due to the risk of serotonin syndrome.
When are MAO-I’s usually used
In treatment resistant depression due to dietary and medication restriction. Dosage is also 3x a day so adherence can be difficult
What drugs can interact with MAO-I’s
- SSRI/SNRI (cause serotonin syndrome)
- tryptophan (cause serotonin syndrome)
- mirtazapine
- phenyephrine
How is a hypertensive crisis treated?
phentolamine infusion
What are serotonin antagonist/reuptake inhibitors (SARI)?
It is an antidepressant often used when sedation is needed and to augment other antidepressants
Give an example of SARI’s
Trazodone
What are the side effects of SARI’s?
- GI upset
- sedation (TAKE meds at NIGHT)
- dizziness
- tiredness
- hypotension/syncope
- blurred vision
- oedema
- priapism
