Phenelzine
Phenelzine is an MAO inhibitor antidepressant used for certain types of depression, usually after other antidepressants have not worked.
🧬 Where this information comes from Click to expand
The clinical label records used on this page are FDA-filed Structured Product Labeling (SPL) retrieved through openFDA. We identified 3 clinical label sets within the page’s selected clinical scope after exact ingredient or ingredient-combination matching and applicable route/form matching. Forms, routes, brands, labelers, strengths, and NDC product-record counts are built separately from matching FDA National Drug Code Directory records. The linked DailyMed document is a representative official source for verification, not the page’s only clinical source. View the linked label on DailyMed →
Phenelzine (Nardil) is an MAO inhibitor antidepressant that blocks monoamine oxidase, an enzyme found throughout the body, and a specialist choice for depression mixed with anxiety, usually after more common antidepressants have failed; on the market since about 1961, it is available as a generic. Side effects are common but often manageable, mainly dizziness, drowsiness or poor sleep, dry mouth and weight gain. Watch for a hypertensive crisis (dangerously high blood pressure) after aged or fermented foods or interacting medicines, signaled by a sudden severe headache or pounding heartbeat, and for worsening mood or suicidal thoughts, the subject of its boxed warning for children, teens and young adults.
Clinical pearls
- Avoid aged, cured and fermented foods high in tyramine, such as aged cheese, dry sausage, yeast extract, beer and wine.
- Tell every dentist and surgeon you take it; meperidine and the cough suppressant dextromethorphan must never be combined with it.
- Never overlap it with other MAO inhibitors or serotonin-type antidepressants, and allow a five-week gap after stopping fluoxetine.
- Do not stop it suddenly, since withdrawal can bring vivid nightmares, agitation or seizures; it is tapered over several weeks.
⚠️ FDA Boxed Warning — the FDA’s strongest safety alert ▾
Antidepressants, including Phenelzine, can increase the risk of suicidal thoughts and behavior in children, teens, and young adults. Phenelzine is not approved for use in children.
Studies did not show this increased risk in adults over 24, and risk was lower in adults 65 and older. Depression itself also raises suicide risk. Anyone starting an antidepressant should be watched closely for worsening mood, suicidal thoughts, or unusual behavior changes. Families and caregivers should stay in close contact with the prescriber.
Patient information guide A plain-language walkthrough of Phenelzine, written from its FDA label.
What Phenelzine is used for
▾
Phenelzine is used for a specific group of depression types.
- Depression described as “atypical,” “nonendogenous,” or “neurotic,” often with mixed anxiety and depression and phobic or hypochondriacal features (Phenelzine Sulfate and Nardil tablets).
- People who have not responded to more commonly used antidepressants. It should rarely be the first one tried.
- Less conclusive evidence exists for severe depression with endogenous features.
How Phenelzine works
▾
Phenelzine is a potent inhibitor of monoamine oxidase (MAO), an enzyme found widely in the body. Blocking it causes many effects. It is not known whether MAO inhibition itself, other actions, or both explain how it helps depression.
Phenelzine dosage
▾
Phenelzine is taken by mouth as a tablet. Treatment usually starts with a tablet three times a day, then the dose is raised fairly quickly as you tolerate it.
- Many people do not respond until at least 4 weeks at the full treatment dose.
- After maximum benefit, the dose is lowered slowly over several weeks.
- Some people stay on a low maintenance dose, taken daily or every other day, for as long as needed.
Follow your prescriber and label directions.
Dosing details from the FDA-approved label
From the Phenelzine prescribing information (“Dosage and Administration”). Doses are set by your prescriber for your product, condition, kidney function and age — never change a dose on your own.
- Initial dose
- One tablet (15 mg) three times a day
- Early phase treatment
- Dosage should be increased to at least 60 mg per day at a fairly rapid pace consistent with patient tolerance
- Many patients do not show a clinical response until treatment at 60 mg has been continued for at least 4 weeks
- Maximum: up to 90 mg per day may be necessary to obtain sufficient MAO inhibition
- Maintenance dose
- After maximum benefit is achieved, dosage should be reduced slowly over several weeks
- May be as low as one tablet, 15 mg, a day or every other day, continued for as long as is required
- Elderly patients (65 and over)
- Dose selection should be cautious, usually starting at the low end of the dosing range
- reflects greater frequency of decreased hepatic, renal, or cardiac function, and of concomitant disease or other drug therapy
Read the label’s full dosing text
DOSAGE AND ADMINISTRATION Initial dose The usual starting dose of Phenelzine Sulfate Tablets is one tablet (15 mg) three times a day. Early phase treatment Dosage should be increased to at least 60 mg per day at a fairly rapid pace consistent with patient tolerance. It may be necessary to increase dosage up to 90 mg per day to obtain sufficient MAO inhibition. Many patients do not show a clinical response until treatment at 60 mg has been continued for at least 4 weeks. Maintenance dose After maximum benefit from Phenelzine Sulfate Tablets is achieved, dosage should be reduced slowly over several weeks. Maintenance dose may be as low as one tablet, 15 mg, a day or every other day, and should be continued for as long as is required.
Read the full Dosage and Administration section on DailyMed →
Phenelzine side effects
▾
Side effects are usually mild or moderate, often ease with time, and can be reduced by adjusting the dose.
Common side effects
- Dizziness
- Headache
- Drowsiness
- Sleep problems (trouble sleeping or sleeping too much)
- Fatigue and weakness
- Constipation
- Dry mouth
- Weight gain
- Tremors, twitching
- Low blood pressure when standing, swelling (edema)
- Sexual side effects
When to get medical help
- Call your doctor right away if you have new or worsening depression, suicidal thoughts, or unusual changes in behavior.
- Get help right away for a severe headache, a pounding or irregular heartbeat, or other signs of a hypertensive crisis (dangerously high blood pressure), especially after certain foods or medicines.
- Seek care for yellowing of the skin or eyes (jaundice), which can signal liver damage.
- Get help for high fever with muscle stiffness, marked sweating, agitation, or confusion.
- Report convulsions (seizures), hallucinations, or severe agitation.
- Tell your doctor about blurred vision or eye pain, since angle-closure glaucoma has been reported.
- Do not stop suddenly. Withdrawal can cause vivid nightmares, agitation, psychosis, or seizures within 1 to 3 days.
Seek help for severe headache, seizures, jaundice, high fever with stiff muscles, or worsening mood. Stopping suddenly can cause withdrawal symptoms.
Phenelzine warnings and precautions
▾
- Suicidality: Antidepressants can raise the risk of suicidal thoughts in children, teens, and young adults. Watch for worsening or unusual behavior, especially early in treatment.
- Hypertensive crisis: Certain foods and drugs can cause dangerously high blood pressure.
- Liver damage: Rare fatal liver injury has been reported.
- Surgery: Elective surgery with general anesthesia should be avoided. Stop it at least 10 days beforehand.
- Withdrawal: Abrupt stopping can cause nightmares, agitation, psychosis, or seizures.
Phenelzine interactions
▾
Phenelzine interacts with many drugs and foods.
- Other MAO inhibitors: risk of hypertensive crisis and seizures.
- Serotonin-type antidepressants: risk of serious reactions with fever, rigidity, and death. Wait 14 days, or 5 weeks after fluoxetine.
- Bupropion and buspirone: risk of high blood pressure or serious reactions.
- Meperidine: can cause severe, even fatal reactions.
- Dextromethorphan, alcohol, and certain narcotics: should not be combined.
- Amphetamines, cocaine, methylphenidate, and similar drugs: can cause hypertensive crisis.
- Guanethidine: can cause moderate to severe high blood pressure.
- Tyramine-rich foods such as aged cheese, cured meats, beer, wine, and yogurt: can raise blood pressure.
Interactions listed in the FDA-approved label
From the Phenelzine prescribing information (“Drug Interactions”): what the manufacturer studied or reported to the FDA.
- Serotoninergic agents (e.g., dexfenfluramine, fluoxetine, fluvoxamine, paroxetine, sertraline, citalopram, venlafaxine): In patients receiving nonselective MAO inhibitors with serotoninergic agents there have been reports of serious, sometimes fatal, reactions. Phenelzine Sulfate Tablets should not be used concomitantly with a serotoninergic agent (See CONTRAINDICATIONS).
- Guanethidine: Administration of guanethidine to patients receiving an MAO inhibitor can produce moderate to severe hypertension due to release of catecholamines. At least two weeks should elapse between withdrawal of the MAO inhibitor and the initiation of guanethidine (see CONTRAINDICATIONS).
Read the label’s full interactions text
Drug Interactions In patients receiving nonselective monoamine oxidase (MAO) inhibitors in combination with serotoninergic agents (e.g., dexfenfluramine, fluoxetine, fluvoxamine, paroxetine, sertraline, citalopram, venlafaxine) there have been reports of serious, sometimes fatal, reactions. Because Phenelzine Sulfate Tablets is a monoamine oxidase (MAO) inhibitor, Phenelzine Sulfate Tablets should not be used concomitantly with a serotoninergic agent (See CONTRAINDICATIONS ). Administration of guanethidine to patients receiving an MAO inhibitor can produce moderate to severe hypertension due to release of catecholamines. At least two weeks should elapse between withdrawal of the MAO inhibitor and the initiation of guanethidine. (see CONTRAINDICATIONS ) Geriatric Use Clinical studies of Phenelzine Sulfate Tablets did not include sufficient numbers of subjects aged 65 and over to determine whether they respond differently from younger subjects. Other reported clinical experience has not identified differences in responses between the elderly and younger patients. In general, dose selection for an elderly patient should be cautious, usually starting at the low end of the dosing range, reflecting the greater frequency of decreased hepatic, renal, or cardiac function, and of concomitant disease or other drug therapy.
Not a complete list. The label covers the interactions the manufacturer studied or reported, and our own interaction database does not cover every medicine either. Bring your full medication list, including vitamins and herbal products, to your pharmacist.
Before taking Phenelzine
▾
- Do not use if allergic to it or its ingredients.
- Do not use with pheochromocytoma, heart failure, severe kidney disease, a history of liver disease, or abnormal liver tests.
- Not approved for children.
- Young people need close monitoring for suicidal thoughts.
- Older adults should usually start at the low end of dosing.
- Tell your care team before any surgery or dental procedure involving anesthesia.
Phenelzine overdose
▾
Overdose can cause drowsiness, agitation, severe headache, hallucinations, seizures, fast or irregular pulse, high or low blood pressure, high fever, and coma. Symptoms may be minimal for the first 12 hours and peak at 24 to 48 hours. Death has been reported, so immediate hospitalization and close monitoring are essential.
What Phenelzine does in the body
▾
Phenelzine inhibits monoamine oxidase, an enzyme found throughout the body, which produces many different effects. The label notes it is unknown whether this inhibition alone or other actions explain its clinical effects.
How your body processes Phenelzine
▾
After a single dose, blood levels peak in about 43 minutes. Phenelzine is extensively broken down, mainly by the MAO enzyme. About 73% of a dose was recovered in urine as breakdown products within 96 hours. The average half-life after a single dose is about 11.6 hours.
How to store Phenelzine
▾
Store between 15° – 30°C (59° – 86°F).
Written from the FDA-approved label with AI and reviewed by our pharmacy team. How we use AI →
Supplements & herbs that interact with Phenelzine
144 supplements and herbal products have documented interactions with Phenelzine in the licensed clinical database we use. Most are manageable — but your pharmacist should know about everything you take, including vitamins and herbals.
- Major · 18
- Moderate · 111
- Minor · 15
Educational information from a licensed clinical database (Natural Medicines) — see our data sources & update cadence. Not medical advice: an interaction being documented does not mean it will happen to you; do not start or stop medications or supplements without professional guidance.
Nutrient depletion considerations
Phenelzine has been associated with lower levels of 1 nutrient in the clinical literature. This does not mean a deficiency will occur — it means these may be worth discussing with your pharmacist or healthcare provider, especially with long-term use.
Educational information from a licensed clinical database (Natural Medicines) — not medical advice. Do not start or stop medications or supplements without professional guidance.
Phenelzine: pharmacist answers to common questions
Quick, plain-English answers to the questions patients ask most about Phenelzine — the kind of thing our pharmacy team would talk through with you at the counter.
What is Phenelzine used for?
▾
How long until it starts working?
▾
Are there foods I need to avoid?
▾
Can I take cold medicine or other drugs with it?
▾
What side effects are normal?
▾
Can I stop it if I feel better?
▾
Is Phenelzine available over the counter?
▾
When was Phenelzine first available?
▾
Who makes Phenelzine?
▾
Answers drafted from the FDA-approved label with AI and reviewed by our pharmacy team. How we use AI →
More about Phenelzine on HelloPharmacist
Phenelzine forms and strengths (how it comes)
Phenelzine is available in 1 form. Different forms and brands can have different approved uses, doses, schedules, and directions. Follow the instructions for your exact product, and do not switch forms without guidance from your prescriber or pharmacist.
Tablet
How this form is used
- Nardil and Phenelzine Sulfate tablets are used for depression described as “atypical,” “nonendogenous,” or “neurotic.”
- Nardil and Phenelzine Sulfate tablets are more suitable for people who failed to respond to more commonly used antidepressants.
- Nardil and Phenelzine Sulfate tablets are taken by mouth, usually several times a day when starting.
- Nardil and Phenelzine Sulfate tablets may take at least 4 weeks at the full treatment dose before a response is seen.
- Nardil and Phenelzine Sulfate tablets should be lowered slowly over several weeks after maximum benefit is reached.
Phenelzine on the U.S. market: products, makers and brands
How Phenelzine appears in the FDA’s National Drug Code Directory — including its dosage forms, strengths, brand names, manufacturers, and FDA-listed product records. These are directory records, not sales or prescription volume.
3 companies list 3 Phenelzine product records with the FDA, mostly as tablet; the earliest marketing or approval year on record is 1961. Brand names on the directory include Nardil; the rest are generics.
Also listed with the FDA, not a patient dose form: Powder (3) — bulk drug substance sold to compounders/manufacturers and multi-item kits. These aren’t counted in the dose-form total above.
Share of FDA-listed product records by manufacturer — FDA National Drug Code Directory. Record counts are not sales or prescription volume.
How widely Phenelzine is used (Medicaid data)
A general measure of how commonly Phenelzine is prescribed, based on Medicaid — one of the largest public drug programs. The figure below is prescriptions filled in Q1–Q4 2025, summed across every form and brand of the drug.
Think of this as a proxy for how widely Phenelzine is used, drawn from freely available public data. Medicaid is just one program — these numbers don’t include Medicare, other government coverage, or commercial and cash-pay prescriptions, so real-world use is higher than what’s shown here.
How commonly is Phenelzine prescribed? Of the 1,601 medications we measure, Phenelzine ranks #1,255 by Medicaid prescriptions — more than 22% of them.
Utilization by Phenelzine product
Pick a product to see its own Medicaid numbers. Each chip is one clinical product — a specific strength & dosage form as defined by RxNorm — with brand-name and generic versions combined.
phenelzine 15 MG Oral Tablet
Summed across the 1 of 3 listed NDC products with Medicaid activity — every brand and generic of this exact strength & form. RxNorm 312347
Shares are of the Medicaid prescriptions shown here. Product grouping follows RxNorm (the National Library of Medicine’s drug terminology), so “one product” means one strength & dosage form regardless of manufacturer. Dollar figures are gross Medicaid reimbursement before mandatory rebates — rebates (often large, especially for brand-name drugs) are confidential, so actual net cost to Medicaid is lower than shown.
Source: Medicaid State Drug Utilization Data (CMS), aggregated by generic ingredient — summed across every NDC (all brands, strengths, salt forms and dosage forms) of Phenelzine, and across all states and both fee-for-service and managed-care claims. A general popularity signal; it excludes Medicare, commercial insurance and cash prescriptions, so it is not total U.S. use. Based on the 1 of 3 listed Phenelzine NDCs with Medicaid activity.
Compare Phenelzine products
A representative set of FDA-listed product records for Phenelzine — across manufacturers, strengths, and dosage forms, grouped by form with each product’s manufacturer and how the FDA approved it. The same medicine may be made and packaged by different companies, so a single drug can have many directory entries. (It’s also why a refill can look different — a new shape, color, or box — even though it contains the same medication.)
| Strength | Route | Manufacturer / Labeler | Category ⓘ | Details |
|---|---|---|---|---|
| 💊Tablet | ||||
| 15 mg | Oral | Lupin Pharmaceuticals,Inc. | ANDA | View NDC → |
| 15 mg | Oral | Mylan Pharmaceuticals Inc. | NDA AUTHORIZED GENERIC | View NDC → |
| 15 mg | Oral | Parke-Davis Div of Pfizer Inc | NDA | View NDC → |
Showing 3 of 3 products — FDA National Drug Code Directory. See every product, package size and price: browse all 3 Phenelzine NDCs →
Phenelzine side effects reported to the FDA (FAERS)
After a medicine reaches the market, patients, doctors and drugmakers can send the FDA reports of problems they think may be linked to it. Here’s what’s been reported for Phenelzine — a signal of what to watch for, not proof the drug caused it.
Source: openFDA, from the FDA Adverse Event Reporting System (FAERS). These are voluntary reports — they don’t prove the drug caused the effect, and counts reflect how often something was reported, not how often it actually happens. Reports also often name the very problem the medicine is taken for — a common reason to file one is that the drug didn’t help — so for a pain reliever you may see “pain” high on the list; that points to why the report was filed, not to the drug causing the symptom. This counts every report that lists Phenelzine in any role, so the total runs higher than the FDA’s official dashboard, which counts only cases where the drug is the suspect. For the authoritative figures, see the FDA FAERS Public Dashboard. Always talk to your pharmacist or doctor.
Phenelzine FDA approval history
How Phenelzine went from FDA review to the pharmacy shelf — the key milestones in its regulatory journey.
Source: Drugs@FDA.
Phenelzine recall history
A recall is when a specific batch of a medicine is pulled from the market — usually a manufacturing issue, not a problem with the drug itself. Class I is most serious, Class III least.
The FDA’s enforcement reports list no Phenelzine recalls since July 2021.
✅No Phenelzine recalls on record since July 2021Source: FDA enforcement (recall) reports, via openFDA; our copy was last updated Sep 24, 2026.
RxNorm Concept Web — From Ingredient to Every Form and Strength
This page starts with one ingredient concept (IN). The branches below show its dose-form concepts (SCDF), then the available clinical drug and strength concepts (SCD). Combination products remain separate concepts with their own pages.
RxCUI 8123 1 dose form · 1 strength
-
Dose form (SCDF) Oral Tablet RxCUI 373308In current FDA listingsClinical drug / strength (SCD) 15 MGRxCUI 312347
Look up RxCUI 8123 in the RxCUI Atlas →
RxNorm is the U.S. National Library of Medicine’s normalized drug vocabulary. Its concept hierarchy can include forms that are not currently marketed; the status on each branch compares that concept with current FDA listings. RxCUIs identify vocabulary concepts, not individual packages or manufacturers.
Phenelzine supply and shortage status
Whether Phenelzine is in short supply in the U.S. right now, plus any shortage history the FDA has on record. A shortage usually reflects a manufacturing or demand issue — not a safety problem with the drug.
Source: openFDA, from the FDA Drug Shortages database.
💵 What Phenelzine costs pharmacies (NADAC benchmark)
The national average invoice price pharmacies pay for the drug itself, from CMS's NADAC survey (data as of Mar 11, 2026). This is a supply-cost benchmark — not a retail price and not what you'd pay at the counter.
| Form | Strength | Pharmacy acquisition benchmark | |
|---|---|---|---|
| Tablet, Film Coated · Oral | 15 mg | $2.53 per tablet | NDC details & price history |
| Tablet · Oral | 15 mg | $0.570 per tablet | NDC details & price history |
Source: CMS National Average Drug Acquisition Cost (NADAC), a survey of retail pharmacy invoice prices. Benchmarks shown are the range across package sizes of a representative product for each form and strength — other manufacturers' products may differ.
Phenelzine brand names
Phenelzine is sold under one brand name in the FDA directory — Nardil. A brand and its generic contain the same active ingredient; the brand name belongs to one company's product.
Who makes Phenelzine: manufacturers and labelers
3 companies list Phenelzine products with the FDA. By number of product records, the largest are Lupin Pharmaceuticals,Inc., Mylan Pharmaceuticals Inc., Parke-Davis Div of Pfizer Inc. Labelers include manufacturers and repackagers; the product in your bottle depends on which one your pharmacy stocks.
Phenelzine drug class (RxNorm)
Phenelzine belongs to the Monoamine Oxidase Inhibitor class.
Classified by RxNorm RxClass — the U.S. National Library of Medicine's standardized drug-classification service (Established Pharmacologic Class from the FDA, the ATC drug family from the WHO, and mechanism of action). Reference only, not medical advice.
Sources for this Phenelzine page
Core label, product, RxNorm, safety, and utilization data on this page come from the sources identified below. AI-written, editorial, and licensed sections are labeled separately.
How this page is built
HelloPharmacist combines public FDA and NLM records and does not author the underlying clinical facts. The plain-language sections are written with AI from the FDA-approved label text and reviewed by our pharmacy team before publication. Greenstone LLC is the representative DailyMed label linked for verification and dates. This is general education, not medical advice: always talk to your doctor or pharmacist about your own medicines. How we build and review drug pages →