Phenelzine
A non-selective, irreversible MAOI used for depression, mainly atypical depression or depression other drugs have not helped.
Drug card
- Class
- MAOI
- How it works
- Inhibiting monoamine oxidase, so serotonin, norepinephrine and dopamine rise
- Used for
- Depression that has not responded to other drugs
- Atypical depression with anxiety or phobic features
- Known for
- Hypertensive crisis after tyramine-rich food
- Serotonin syndrome with serotonergic drugs
- Dizziness on standing (postural hypotension)
Study it as a flashcard, and it comes back before you forget it.
Mechanism of action
How does phenelzine work?
Phenelzine is a hydrazine MAOI. MAO oxidizes it to a reactive intermediate that then attacks and inactivates the enzyme's flavin group, so the block is irreversible and non-selective. Maximal inhibition builds over 5 to 10 days, and the antidepressant effect can take several weeks.
Uses
What is phenelzine used for?
- Depression that has not responded to other drugs
- Atypical depression with anxiety or phobic features
Side effects
Side effects of phenelzine
- Hypertensive crisis after tyramine-rich foodKnown forSerious
- Serotonin syndrome with serotonergic drugsKnown forSerious
- Dizziness on standing (postural hypotension)Known for
- Drowsiness and tiredness
- Trouble sleeping
- Weight gain
- Swelling from fluid retention (edema)
- Sexual problems, such as anorgasmia or impotence
- Dry mouth and constipation
- Liver damage, rarely fatalSerious
- Suicidal thoughts in children and young adultsSerious
- Withdrawal symptoms if stopped abruptly
Known for marks what an exam expects you to know it for.
Watch for
Cautions and what sets it apart
- Avoid tyramine-rich foods and drinks during treatment and for 2 weeks after stopping.
- Contraindicated with sympathomimetics (amphetamines, methylphenidate, epinephrine), levodopa and serotonergic antidepressants.
- Contraindicated in pheochromocytoma, heart failure, severe kidney disease and liver disease.
- Allow 14 days after stopping it before another antidepressant, and 5 weeks after fluoxetine before starting it.
Good to know: Rarely a first choice: it is kept for people whose depression has not responded to the antidepressants more commonly used.
Remember it
A way to remember it
Say cheese, think crisis.
Aged cheese and other tyramine-rich foods can set off a hypertensive crisis in someone taking a non-selective MAOI, so these foods are avoided during treatment and for two weeks after it stops.
Written for biofideX
Its class
Monoamine oxidase inhibitors
MAOIs inhibit monoamine oxidase, the enzyme that deaminates and so inactivates serotonin, norepinephrine and dopamine, which leaves more of them available in nerve endings; how this relieves depression is not fully known. Older MAOIs such as phenelzine are non-selective and irreversible. Tyramine in food is also a monoamine, so with MAO blocked, tyramine-rich food can trigger a hypertensive crisis.
Easily mixed up with tricyclic antidepressants and MAO-B inhibitors.
Sources
Checked against
Written for biofideX in plain words, after checking these references:
- Phenelzine sulfate tablets: label (DailyMed)
- Phenelzine 15 mg film-coated tablets: SmPC (emc)
- Phenelzine (NCI Thesaurus)
For learning pharmacology, not for treatment decisions: no doses are given, and a prescriber, pharmacist or the product's own label is the word on any one patient. Spotted a mistake? Tell us and we'll correct it.
Depression, anxiety and sleep
Phenelzine is one of 15 drugs practiced together here: their classes, how they work, what they treat and what they're known for.
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