Phenelzine and Atenolol: Interaction Details
AI-assisted, pharmacist-reviewed · AI content regenerated Jul 15, 2026 · Source data updated Jul 11, 2026 · Sources: FDA labeling, DDInter 2.0, cited literature
Phenelzine
Atenolol
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.
Phenelzine (Nardil) is an antidepressant, and atenolol (Tenormin) is a beta blocker that lowers blood pressure and slows your heart rate. When taken together, they can add up, so your blood pressure may drop more than expected and your pulse may get too slow. You might feel dizzy, lightheaded, or very tired, especially when standing up.
The good news is that this is manageable. Your care team can watch your blood pressure and heart rate and adjust your doses if needed. Please don't stop or change either medicine on your own. Just let your pharmacist or doctor know about any dizziness or a slow, pounding, or faint feeling.
Effect: Additive risk of exaggerated hypotension and bradycardia when phenelzine (a nonselective MAOI) is combined with atenolol (a beta-1 selective blocker).
- Direction: Enhanced hypotensive/bradycardic PD effect. Neither agent requires bioactivation here.
- Mechanism: Unknown/theoretical; likely additive cardiovascular depression.
- Evidence: Theoretical, supported by two case reports (patients >63 yr, phenelzine >30 mg/day added to nadolol or metoprolol) with significant pulse drop at 8 to 11 days.
- Onset: Unspecified (reports suggest delayed, ~1 to 1.5 weeks).
- Management: Monitor BP and heart rate; individualize/titrate doses. Watch for orthostasis, symptomatic bradycardia.
What happens
An increased risk of exaggerated hypotensive effect and an increased risk of bradycardia
Interaction Deep Dive
Caution is warranted when phenelzine is given together with antihypertensive agents such as beta blockers, because the combination can produce exaggerated hypotensive effects 1. Two case reports described elderly patients (over 63 years) in whom phenelzine (more than 30 mg per day) was introduced alongside existing nadolol or metoprolol treatment; within eight to eleven days these patients experienced a marked reduction in pulse rate 2.
Why it happens (mechanism)
Unknown
How to manage this interaction
What your care team may do:
- Check your blood pressure and pulse more closely, especially in the first couple of weeks after both drugs are being used together.
- Adjust and individualize your doses if your pressure drops too low or your heart rate slows too much.
What you can do:
- Keep taking both medicines exactly as prescribed unless your doctor tells you otherwise.
- Rise slowly from sitting or lying down to avoid dizziness.
- Report dizziness, fainting, unusual tiredness, or a slow/weak pulse to your pharmacist or prescriber.
Management is individual — confirm any change with your pharmacist or prescriber.
Literature reports
1 report — tap to read
a) A 75-year-old man experienced bradycardia of 46 to 50 beats per minute, down from a baseline of 62 to 80 beats per minute, 8 days after phenelzine 30 mg to 60 mg daily was added to a regimen that included oral nadolol 40 mg daily. When the nadolol dose was lowered to 20 mg daily, the pulse rate rose back 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 ongoing oral metoprolol therapy (150 mg daily). Discontinuing the metoprolol while maintaining the phenelzine at the same dose brought the pulse rate back to baseline values. The mechanism underlying this interaction is not clear, but it may involve altered pharmacodynamic responses 2.
Common questions
Can I take Phenelzine and Atenolol together?
Combining phenelzine and atenolol can lower your blood pressure and heart rate more than either alone, so your care team may monitor you and adjust doses. Keep taking both as prescribed and report dizziness or a slow pulse. Always confirm with your pharmacist or prescriber before making any change.
How serious is the Phenelzine and Atenolol 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 is the Phenelzine and Atenolol interaction managed?
What your care team may do: Check your blood pressure and pulse more closely, especially in the first couple of weeks after both drugs are being used together. Adjust and individualize your doses if your pressure drops too low or your heart rate slows too much. What you can do: Keep taking both medicines exactly as prescribed unless your doctor tells you otherwise. Rise slowly from sitting or lyin… Management is individual — always follow your own care team's guidance.
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 Phenelzine or Atenolol 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)
- 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
- Reggev A & Vollhardt BR: Bradycardia induced by an interaction between phenelzine and beta blockers. Psychosomatics 1989; 30:106-108. PubMed
Keep reading about Phenelzine
Keep reading about Atenolol
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