Irreversible MAOI·Psychiatry - Antidepressants

Phenelzine

Severe Treatment-Resistant Depression, Atypical Depression (hyperphagia, hypersomnia, leaden paralysis), severe Panic/Social anxiety

Authority requiredPBSMAOINardil15 mg tablet+2

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At a glance

Max Dose

90 mg/day

Half-life

11 h

High risk: Diet Restrictions

CRITICAL

High risk: Hypertensive Crisis

RISK

Cautions

Avoid / Cautions

Non-compliance. If the patient cannot be trusted to follow the strict diet, do not prescribe this drug. Pheochromocytoma, heart failure, severe liver disease. Pregnancy Category B3 (Avoid due to intense BP fluctuations).

Where it stands

Rapid Summary

Overview

Irreversible Monoamine Oxidase Inhibitor (MAOI). The most potent class of antidepressants in existence. Highly effective for severe, atypical, treatment-resistant depression.

Clinical Focus

Permanently destroys the MAO enzyme in the gut and brain. Eating Tyramine-rich foods (cheese, wine) causes a fatal hypertensive crisis (stroke/death).

Bottom Line

Phenelzine is an irreversible MAOI for treatment-resistant depression and social phobia, but requires strict dietary tyramine restriction and has potentially fatal interactions with serotonergic drugs.

Formulation & Access

Brand Names

Nardil

Oral Routes

Tablets (15 mg).

Prescribing & PBS

Authority Required (PBS). Initiated by Psychiatrists only.

Indications & Use

Primary

PBSTGA

Severe Treatment-Resistant Depression, Atypical Depression (hyperphagia, hypersomnia, leaden paralysis), severe Panic/Social anxiety.

Clinical Place

Last line of defense in psychiatry when SSRIs, SNRIs, TCAs, and ECT have completely failed.

Quick reference

Class & Role

Irreversible MAOI — Irreversible Monoamine Oxidase Inhibitor (MAOI).

Route / Formulation

Tablets (15 mg). (Nardil)

Usual Dose & Max

Start PO 15 mg BD or TDS. Titrate up to 60-90 mg/day. Reduce to maintenance dose (15-30 mg/day) once remission is achieved. Max 90 mg/day (e.g., 30 mg TDS).

Key Indication Doses

Treatment Resistant Depression: Start PO 15 mg BD or TDS. Titrate up to 60-90 mg/day. Reduce to maintenance dose (15-30 mg/day) once remission is achieved. Washout Period: Must wait 14 days after stopping an SSRI (or 5 weeks after Fluoxetine) before starting Phenelzine.

Best Uses

Key Risks

Cardiovascular: Hypertensive Crisis (Tyramine reaction: sudden explosive headache, stiff neck, vomiting, stroke, death). HIGH — Paradoxical postural hypotension (very common baseline side effect). Neurological: Fatal Serotonin Syndrome (if mixed with SSRIs). HIGH — Insomnia, daytime somnolence, B6 deficiency (neuropathy). Metabolic: Massive weight gain, peripheral edema.

Key Interactions

Aged cheeses (Cheddar, Brie), cured meats (salami), tap beer, red wine, Marmite/Vegemite, soy sauce. (These contain Tyramine. Without MAO in the gut to destroy it, Tyramine floods the blood, forcing massive noradrenaline release). SSRIs, TCAs, Tramadol, Dextromethorphan (Cough syrup), Pseudoephedrine (Cold meds), Adrenaline. ALL ARE FATAL.

Monitoring

Strict dietary counseling. Provide the patient with an 'MAOI Alert Card'. Monitor BP for both severe postural drops and hypertensive spikes. Routine LFTs (rare hepatotoxicity).

Clinical Pearl

If a patient eats a block of aged cheese and presents to ED with a BP of 240/140 and a pounding headache, you must treat the hypertensive crisis with IV Phentolamine or GTN infusion. Do not use beta-blockers.

Access

Authority requiredNardil15 mg tablet

Brand: Nardil
PBS status: Authority required
Formulation: Tablets (15 mg).

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