What MAOI (Monoamine Oxidase Inhibitor) medications start with the letter P?

MAOI Medications That Start with P

The only MAOI medication that starts with the letter P is phenelzine (Nardil). 1, 2

Phenelzine: Clinical Information

Mechanism of Action

• Phenelzine is a potent, irreversible inhibitor of monoamine oxidase (MAO) that belongs to the hydrazine derivative class 2
• It works by preventing the breakdown of neurotransmitters such as serotonin, norepinephrine, and dopamine in the brain, thereby increasing their availability 2

Clinical Uses

• Indicated for treatment-resistant depression, particularly melancholic depression 3
• Effective for atypical depression and bipolar depression 4
• Used in the treatment of certain anxiety disorders with high levels of anxiety 1
• Should be considered before electroconvulsive therapy in appropriate cases 3

Dosing

• Available as 15 mg oral tablets 2
• Typically started at lower doses and titrated based on response and tolerability 3

Important Safety Considerations

Contraindications

• Hypersensitivity to phenelzine or its ingredients 2
• Pheochromocytoma, congestive heart failure, severe renal impairment 2
• History of liver disease or abnormal liver function tests 2
• Concomitant use with:
  • Other MAOIs (including tranylcypromine, isocarboxazid, pargyline) 2
  • Sympathomimetic drugs (amphetamines, cocaine, methylphenidate) 2
  • Serotonergic agents (SSRIs, SNRIs) 2
  • Meperidine and other opioids 2
  • Dextromethorphan 2
  • Buspirone 2
  • Bupropion 2
  • Tryptophan supplements 2

Drug Interactions

• Requires at least 14 days washout period when switching to or from other antidepressants 1
• Requires 5 weeks washout period when switching from fluoxetine 2
• Can cause potentially fatal serotonin syndrome when combined with serotonergic medications 5
• Contraindicated with guanethidine 2

Dietary Restrictions

• Patients must avoid foods high in tyramine to prevent hypertensive crisis 6
• Restricted foods include:
  • Aged cheeses 2
  • Fermented, aged, or smoked meats 2
  • Broad bean pods (fava beans) 2
  • Aged or fermented products (sauerkraut, kimchi) 2
  • Tap/draft beers and some wines 2
  • Excessive amounts of caffeine and chocolate 2

Metabolism

• Metabolized through multiple pathways including acetylation (minor pathway) 7
• Produces metabolites including phenylacetic acid and p-hydroxyphenylacetic acid 7
• May elevate brain GABA levels through metabolic pathways 7

Other MAOIs (Not Starting with P)

For completeness, other MAOIs include:

• Tranylcypromine (irreversible, non-selective MAOI) 3
• Isocarboxazid (irreversible, non-selective MAOI) 3
• Selegiline (MAO-B selective at lower doses) 4
• Moclobemide (reversible MAO-A inhibitor) 4

Clinical Pearls

• Despite recommendations in treatment guidelines, MAOIs like phenelzine are underutilized in clinical practice 4
• Modern food production has reduced tyramine content in many foods, making dietary restrictions more manageable than historically believed 6
• MAOIs should not be considered drugs of last resort but may be appropriate earlier in treatment algorithms for specific depression subtypes 3
• Patients should be educated about recognizing signs of serotonin syndrome and hypertensive crisis 1
• Phenelzine should be discontinued at least 10 days prior to elective surgery requiring general anesthesia 2