Ampicillin 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
Atenolol
Ampicillin
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 atenolol (a blood pressure and heart medicine) along with the antibiotic ampicillin. Here's the simple version: taking them together can lower how much atenolol your body actually absorbs, so the atenolol may work a little less well while you're on the antibiotic. That could mean your blood pressure runs slightly higher than usual.
The good news is this is considered a minor interaction, and the real-world effect is often small. Your care team can easily handle it by checking your blood pressure and adjusting your atenolol if needed. Keep taking both as prescribed, and let your pharmacist or doctor know you're on them together.
Effect: Reduced atenolol effectiveness via decreased bioavailability (lower serum concentrations/AUC). Direction is a PD attenuation of beta-blockade, not enzyme-mediated; neither agent is a prodrug here.
- Mechanism: Ampicillin reduces atenolol absorption/bioavailability.
- Magnitude: Dose-dependent; ampicillin 1 g produced a greater fall in atenolol AUC than 250 mg.
- Onset: Rapid. Evidence: Probable (2 studies); clinical significance not established.
- Severity: Minor.
Management: If co-administered, monitor blood pressure and heart rate; titrate/individualize atenolol dose as clinically indicated.
What happens
Decreased atenolol effectiveness
Interaction Deep Dive
Two studies have shown that giving ampicillin and atenolol together lowers atenolol serum levels, though the clinical relevance of this effect remains unproven12. When ampicillin was administered at a higher dose (1 g compared with 250 mg), the reduction in atenolol's AUC was more pronounced2.
Why it happens (mechanism)
Decreased atenolol bioavailability
How to manage this interaction
This is generally a minor interaction, and your care team can manage it easily.
- Keep taking both medicines as prescribed unless your doctor or pharmacist tells you otherwise.
- Your team may monitor your blood pressure more closely while you are on the antibiotic.
- If needed, your atenolol dose may be adjusted and individualized by your care team.
- Ampicillin is usually a short course, so any effect is typically temporary.
Let your pharmacist or prescriber know you are taking these together, and mention any higher-than-usual blood pressure readings or symptoms.
Management is individual — confirm any change with your pharmacist or prescriber.
Literature reports
1 report — tap to read
a) The pharmacokinetics of atenolol was investigated in 6 healthy subjects who took 100 mg of atenolol as monotherapy for 6 days. These same subjects then received atenolol 100 mg together with 1 g ampicillin, 500 mg aspirin, and 300 mg allopurinol. Allopurinol and aspirin did not meaningfully change the kinetics of atenolol, whereas ampicillin lowered the bioavailability, the mean peak plasma levels, the mean steady-state concentration, the urinary recovery, and the area under the plasma concentration-time curve. Exercise tachycardia was significantly greater with the ampicillin plus atenolol combination than with atenolol given alone 1.
Common questions
Can I take Ampicillin and Atenolol together?
Ampicillin can slightly lower how well atenolol works by reducing its absorption, but this is a minor effect that is easily managed with blood pressure monitoring. Keep taking both as prescribed and tell your pharmacist or doctor you're on them together. Always confirm with your pharmacist or prescriber before making any change.
How serious is the Ampicillin and Atenolol interaction?
It is rated minor. Usually limited clinical impact.
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 Ampicillin and Atenolol interaction managed?
This is generally a minor interaction, and your care team can manage it easily. Keep taking both medicines as prescribed unless your doctor or pharmacist tells you otherwise. Your team may monitor your blood pressure more closely while you are on the antibiotic. If needed, your atenolol dose may be adjusted and individualized by your care team. Ampicillin is usually a short course, so any effect i… 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 Ampicillin 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 anything you'd monitor while I'm on both?
References (2)
Keep reading about Atenolol
Keep reading about Ampicillin
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:
major · moderate · minor — check everything you take with our drug–supplement interaction checker.
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