Drug Interaction Report

Ampicillin Injection and Chloroquine: Interaction Details

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

AI-assisted, pharmacist-reviewed · Source data updated Jul 11, 2026 · Sources: FDA labeling, DDInter 2.0, cited literature

Ampicillin Injection

Omnipen-N® Penbritin-S® Polycillin-N® Polyflex Totacillin-N®
+

Chloroquine

Aralen®
Dr. Brian Staiger, PharmD, BCPS
Medically reviewed by
Dr. Brian Staiger, PharmD, BCPS
Updated Jul 11, 2026
Editorial policy · Data sources
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Interaction severity
Moderate
Can be significant — usually manageable with 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 57 documented Ampicillin Injection interactions, 10 are rated moderate — including this one.
Onset
unspecified
Evidence
probable
Severity
Moderate

What happens

Decreased chloroquine bioavailability

Interaction Deep Dive

Concomitant use of ampicillin and chloroquine has resulted in a significant decrease in the bioavailability of chloroquine in a study of healthy volunteers. Separate administration of ampicillin and chloroquine by at least 2 hours12.

Why it happens (mechanism)

Unspecified

Literature reports

1 report — tap to read

a) In a study of healthy volunteers, chloroquine significantly reduced the bioavailability of ampicillin 12.

Common questions

Can I take Ampicillin Injection and Chloroquine together?

Decreased chloroquine bioavailability Always confirm with your pharmacist or prescriber before making any change.

How serious is the Ampicillin Injection and Chloroquine interaction?

It is rated moderate. Can be significant — usually manageable with 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 "probable". Good supporting evidence, though not definitively proven.

Questions for your pharmacist

  • Does my dose of Ampicillin Injection or Chloroquine 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)

  1. US Food & Drug Administration (FDA): Fact sheet for health care providers emergency use authorization (EUA) of chloroquine phosphate supplied from the strategic national stockpile for treatment of COVID-19 in certain hospitalized patients. US Food & Drug Administration (FDA). Silver Spring, MD. 2020.
  2. Product Information: Chloroquine phosphate oral tablets, chloroquine phosphate oral tablets. Rising Pharmaceuticals Inc (per DailyMed), Saddle Brook, NJ, 2018. DailyMed
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Ampicillin Injection

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All Ampicillin Injection interactions (57) Ampicillin Injection drug information
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Chloroquine

Keep reading about Chloroquine

All Chloroquine interactions (332) Chloroquine drug information
Also serious with: Levomethadyl Pimozide Mesoridazine Levoketoconazole
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:

Chloroquine + Activated Charcoal Hibiscus Sabdariffa Biofeedback Coffee Charcoal Dendrobium European Mandrake Fever Bark Ginkgo + 21 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.