Phenelzine Drug Profile

What is Phenelzine?

Phenelzine is a prescription antidepressant medication that belongs to the class of drugs known as monoamine oxidase inhibitors (MAOIs). It is primarily used to treat major depressive disorder, particularly in patients who have not responded adequately to other antidepressant treatments. This medication has been available since the 1960s and remains an important option for treatment-resistant depression.

Uses

Phenelzine is approved and used for several psychiatric conditions:

• Major depressive disorder: Particularly effective for atypical depression characterized by mood reactivity, increased appetite, and hypersomnia
• Treatment-resistant depression: Used when other antidepressants like SSRIs or tricyclics have failed to provide adequate relief
• Social anxiety disorder: Sometimes prescribed off-label for severe social phobia when other treatments are ineffective
• Panic disorder: May be used in cases where first-line treatments have not been successful
• Bulimia nervosa: Occasionally prescribed off-label for eating disorders with depressive components

How it works

Phenelzine works by inhibiting monoamine oxidase enzymes (MAO-A and MAO-B) in the brain and other tissues. These enzymes normally break down neurotransmitters such as serotonin, norepinephrine, and dopamine. By blocking these enzymes, phenelzine increases the availability of these mood-regulating chemicals in the brain, which helps alleviate symptoms of depression and anxiety.

Side effects

Common side effects include:

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• Dizziness and lightheadedness
• Drowsiness or fatigue
• Dry mouth
• Constipation
• Weight gain
• Sexual dysfunction
• Sleep disturbances
• Headache

Serious side effects to watch for:

• Hypertensive crisis (sudden severe high blood pressure)
• Serotonin syndrome when combined with other serotonergic drugs
• Severe liver damage or hepatitis
• Suicidal thoughts, particularly in young adults
• Severe hypotension (low blood pressure)

Warnings and precautions

• Dietary restrictions: Patients must follow a strict tyramine-free diet, avoiding aged cheeses, cured meats, fermented foods, and certain alcoholic beverages to prevent dangerous blood pressure spikes
• Pregnancy and breastfeeding: Should be used only when potential benefits outweigh risks; adequate studies in pregnant women are lacking
• Liver function: Regular monitoring required as phenelzine can cause hepatotoxicity; contraindicated in patients with liver disease
• Elderly patients: Increased risk of falls due to orthostatic hypotension; dosage adjustments may be necessary
• Bipolar disorder: May trigger manic episodes in susceptible individuals; mood stabilizers may be required

Interactions

Phenelzine has numerous potentially dangerous drug interactions:

• SSRIs and SNRIs: Can cause fatal serotonin syndrome; requires 2-week washout period between medications
• Tricyclic antidepressants: May lead to serotonin syndrome and hypertensive crisis
• Sympathomimetics: Including decongestants and stimulants, can cause severe hypertension
• Opioids: Particularly meperidine and tramadol, can trigger serotonin syndrome
• Tyramine-containing foods: Can cause hypertensive crisis requiring emergency treatment
• St. John’s Wort: Herbal supplement that increases serotonin syndrome risk
• Dextromethorphan: Found in cough medications, can cause dangerous CNS effects
• General anesthetics: May interact during surgery; anesthesiologists must be informed

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Dosage

Typical adult dosing for depression begins at 15 mg three times daily, with gradual increases based on patient response and tolerance. The usual effective dose ranges from 60-90 mg per day, divided into multiple doses. Some patients may require up to 90 mg daily for optimal therapeutic effect. Dosage adjustments should be made slowly, typically at intervals of 1-2 weeks. Elderly patients or those with medical conditions may require lower starting doses and more cautious titration. All dosage determinations should be made by a qualified healthcare provider who can monitor for effectiveness and side effects.

Sources: FDA DailyMed drug labels (public domain), BNF, WHO Essential Medicines List. This article is for informational purposes only and does not constitute medical advice. Always consult your healthcare provider before starting or stopping any medication.

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