Drug Interaction Report

Esmolol and Phenelzine: Interaction Details

A pharmacist-reviewed analysis of the Esmolol and Phenelzine interaction: the documented clinical effects, severity rating, onset, mechanism, and management considerations, with cited references throughout.

AI-assisted, pharmacist-reviewed · Source data updated Aug 8, 2026 · Sources: FDA labeling, DDInter 2.0, cited literature

Phenelzine

Nardil
+

Esmolol

Brevibloc
Dr. Brian Staiger, PharmD, BCPS
Medically reviewed by
Dr. Brian Staiger, PharmD, BCPS
Updated Aug 8, 2026
Editorial policy · Data sources
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Interaction severity
Major
Potentially serious — often needs a change or close monitoring.
How we grade severity & evidence

Severity levels

  • Contraindicated: These should generally not be used together.
  • Major: Potentially serious — often needs a change or close monitoring.
  • Moderate: Can be significant — usually manageable with monitoring.
  • Minor: Usually limited clinical impact.

Evidence grades

  • Established: Well documented — supported by controlled studies or strong clinical data.
  • Probable: Good supporting evidence, though not definitively proven.
  • Suspected: Some evidence suggests this interaction, but it is not well established.
  • Possible: Limited or conflicting evidence; the interaction may occur.
  • Theoretical: Predicted from the drugs' pharmacology; not yet confirmed in people.

Ratings come from the documented interaction literature and are reviewed by a pharmacist. They describe the documented risk of the combination, not what will necessarily happen to you — your dose, timing, and health picture all matter.

Of 191 documented Esmolol interactions, 36 are rated major — including this one.
Worried about symptoms right now? Contact your pharmacist or prescriber, or call Poison Control at 1-800-222-1222 (US). Call 911 for an emergency.
Onset
unspecified
Evidence
theoretical
Severity
Major

What happens

An increased risk of exaggerated hypotensive effect and an increased risk of bradycardia

Interaction Deep Dive

Exert caution when phenelzine and antihypertensive drugs, like beta blockers are coadministered, since exaggerated hypotensive effects may result1. In two case reports involving elderly patients (more than 63 years), when phenelzine (more than 30 mg daily) was added to their nadolol or metoprolol therapy, a significant drop in pulse rate occurred after eight to eleven days 2.

Why it happens (mechanism)

Unknown

Literature reports

1 report — tap to read

a) Bradycardia of 46 to 50 beats per minute from a baseline of 62 to 80 beats per minute was described in a 75-year-old man 8 days following the addition of phenelzine 30 mg to 60 mg daily to a regimen of oral nadolol 40 mg daily. With a dose reduction of the nadolol to 20 mg daily, the pulse rate increased to baseline levels. In the second case, a 63-year-old woman developed sinus bradycardia 11 days after phenelzine 60 mg daily was added to chronic oral metoprolol therapy (150 mg daily). Withdrawal of the metoprolol with continuation of the phenelzine at the same dose resulted in a return of the pulse rate to baseline values. The mechanism involved in this interaction is not clear, but may involve altered pharmacodynamic responses 2.

Common questions

Can I take Esmolol and Phenelzine together?

An increased risk of exaggerated hypotensive effect and an increased risk of bradycardia Always confirm with your pharmacist or prescriber before making any change.

How serious is the Esmolol and Phenelzine interaction?

It is rated major. Potentially serious — often needs a change or close monitoring.

How quickly could this interaction happen?

The documented onset is "unspecified". The timing of this interaction is not well characterized.

How strong is the evidence for this interaction?

The evidence is graded "theoretical". Predicted from the drugs' pharmacology; not yet confirmed in people.

Questions for your pharmacist

  • Does my dose of Esmolol or Phenelzine need adjusting while I take them together?
  • What symptoms should prompt me to call you or my prescriber right away?
  • Does the timing of my doses matter for this combination?
  • Is there a safer alternative to one of these medications for me?

References (2)

  1. Product Information: NARDIL(R) oral film coated tablets, phenelzine sulfate oral film coated tablets. Parke-Davis Div of Pfizer Inc (per DailyMed), New York, NY, 2020. DailyMed
  2. Reggev A & Vollhardt BR: Bradycardia induced by an interaction between phenelzine and beta blockers. Psychosomatics 1989; 30:106-108. PubMed
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Beyond drug–drug

These medications also interact with supplements

Prescription drugs aren't the whole picture — herbal and dietary supplements can interact with them too. From the evidence-graded Natural Medicines database:

Esmolol + Activated Charcoal American Hellebore American Mistletoe Indian Snakeroot Tyramine Adrafinil Agmatine Algal Oil + 131 more

major · moderate · minor — check everything you take with our drug–supplement interaction checker.

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This information is for education, not a substitute for professional medical advice. Do not start, stop, or change any medication without talking to your pharmacist or prescriber.