Atenolol and Quinidine: 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
Quinidine
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.
You've been prescribed quinidine (a heart rhythm medicine) and atenolol (a beta blocker). Both of these medicines can slow your heart rate and lower your blood pressure. When taken together, those effects can add up, so your heart may beat more slowly and your blood pressure may dip, especially when you stand up quickly.
Watch for feeling dizzy, lightheaded, very tired, or faint. The good news is that this is very manageable. Your care team can check your heart rate and blood pressure and fine-tune your doses so both medicines work safely together. Keep taking both as prescribed, and let your doctor or pharmacist know if you feel any of these symptoms.
Effect: Additive negative chronotropic and hypotensive effects when quinidine is combined with atenolol.
- Mechanism: Pharmacodynamic additivity, not primarily PK. Both agents depress heart rate; quinidine prolongs QTc and PR, and beta blockade adds to bradycardia and orthostatic hypotension. Atenolol is largely renally cleared and hydrophilic, so CYP-mediated PK interaction is minimal.
- Direction/magnitude: Increased beta-blocking and hypotensive effect; magnitude variable.
- Onset: Rapid. Evidence: Probable.
- Management: Monitor BP and HR (and ECG for PR/QTc) closely. Consider lower initial doses of each agent and individualize titration.
What happens
Bradycardia, hypotension
Interaction Deep Dive
When beta blockers (propranolol, metoprolol, timolol, atenolol) are taken together with quinidine, the combined effect has been described as additive, producing greater beta blockade (slowing of heart rate along with lengthening of the QTc and PR intervals) as well as orthostatic hypotension2341.
Why it happens (mechanism)
Additive cardiovascular effects
How to manage this interaction
This combination can be used safely with the right oversight. Here is what typically happens and what you can do:
- Closer monitoring: Your care team may check your blood pressure and heart rate more often, and may track your ECG.
- Dose tailoring: The starting dose of each medicine may need to be adjusted and individualized by your team.
- Keep taking both exactly as prescribed unless your doctor tells you otherwise.
- Report symptoms: Tell your pharmacist or prescriber about dizziness, lightheadedness on standing, fainting, unusual tiredness, or a very slow heartbeat.
Management is individual — confirm any change with your pharmacist or prescriber.
Literature reports
1 report — tap to read
a) It was reported that giving atenolol together with quinidine produced orthostatic hypotension in a 56-year-old woman 1. Stopping atenolol led to resolution of the symptoms within 2 days.
Common questions
Can I take Atenolol and Quinidine together?
Quinidine and atenolol both slow the heart and lower blood pressure, so together they can cause bradycardia and dizziness; your care team can manage this with closer monitoring and adjusted doses, so keep taking both as prescribed and report any dizziness or slow heartbeat. Always confirm with your pharmacist or prescriber before making any change.
How serious is the Atenolol and Quinidine interaction?
It is rated moderate. Can be significant — usually manageable with monitoring.
How quickly could this interaction happen?
The documented onset is "rapid". Effects can appear quickly, often within about 24 hours of combining the drugs.
How is the Atenolol and Quinidine interaction managed?
This combination can be used safely with the right oversight. Here is what typically happens and what you can do: Closer monitoring: Your care team may check your blood pressure and heart rate more often, and may track your ECG. Dose tailoring: The starting dose of each medicine may need to be adjusted and individualized by your team. Keep taking both exactly as prescribed unless your doctor tells… Management is individual — always follow your own care team's guidance.
How strong is the evidence for this interaction?
The evidence is graded "probable". Good supporting evidence, though not definitively proven.
Questions for your pharmacist
- Does my dose of Atenolol or Quinidine 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 anything you'd monitor while I'm on both?
References (4)
- Manolis AS & Estes NAM: Orthostatic hypotension due to quinidine and atenolol. Am J Med 1987; 82:1083-1084. PubMed
- Zhou HH, Anthony LB, Roden DM, et al: Quinidine reduces clearance of (+)-propranolol more than (-)-propranolol through marked reduction in 4-hydroxylation. Clin Pharmacol Ther 1990; 47:686-693. DOI
- Leemann T, Dayer P, & Meyer UA: Single dose quinidine treatment inhibits metoprolol oxidation in extensive metabolizers. Eur J Clin Pharmacol 1986; 29:739-741. DOI
- Dinai Y, Sharir M, Naveh N, et al: Bradycardia induced by interaction between quinidine and ophthalmic timolol. Ann Intern Med 1985; 103:890-891. PubMed
Keep reading about Quinidine
Keep reading about Atenolol
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