Drug Interaction Report

Amoxicillin and Venlafaxine: Interaction Details

A pharmacist-reviewed analysis of the Amoxicillin and Venlafaxine 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

Venlafaxine

No brand names on record
+

Amoxicillin

Amoxi Drop Amoxi-tabs Amoxil® Amoxil® Pediatric Drops Biomox Dispermox® Larotid® Suspension Moxatag
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
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 68 documented Amoxicillin interactions, 48 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
rapid
Evidence
probable
Severity
Major

What happens

An increased risk of serotonin syndrome

Interaction Deep Dive

A 56-year-old male on venlafaxine experienced serotonin syndrome within 3 hours of taking amoxicillin/clavulanate and had a positive-rechallenge 2 months later1. If amoxicillin/clavulanate and venlafaxine are used concomitantly, monitor closely for symptoms of serotonin syndrome. If serotonin syndrome develops, discontinue the offending agents and provide supportive care and other therapy as necessary 2.

Why it happens (mechanism)

Unknown

Literature reports

1 report — tap to read

a) A 56-year-old male on venlafaxine experienced serotonin syndrome within 3 hours of taking amoxicillin/clavulanate and had a positive-rechallenge 2 months later. He was on venlafaxine 37.5 mg twice daily for 10 months for depression. He experienced tingling in the tip of his tongue, intense paraesthesia in the fingers, severe abdominal cramps, profuse diarrhea, cold sweats, uncontrollable shivering and tremor, agitation, and he was frightened but not confused 2 hours after taking the first dose of amoxicillin/clavulanate 375 mg for gingivitis and dental abscess. The symptoms resolved after 6 hours and then he slept a further 8 hours. No further amoxicillin/clavulanate doses were administered. Two months later he was re-challenged and he developed the same symptoms after the first dose. The patient continued on venlafaxine without further episodes. His medical history includes taking amoxicillin/clavulanate, while at the time not on venlafaxine, without any events 1.

Common questions

Can I take Amoxicillin and Venlafaxine together?

An increased risk of serotonin syndrome Always confirm with your pharmacist or prescriber before making any change.

How serious is the Amoxicillin and Venlafaxine interaction?

It is rated major. Potentially serious — often needs a change or close 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 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 Amoxicillin or Venlafaxine 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. Connor H: Serotonin syndrome after single doses of co-amoxiclav during treatment with venlafaxine. J R Soc Med 2003; 96(5):233-234. PubMed
  2. Boyer EW & Shannon M: The serotonin syndrome. N Eng J Med 2005; 352(11):1112-1120. DOI
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Venlafaxine

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All Venlafaxine interactions (130)
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Amoxicillin

Keep reading about Amoxicillin

All Amoxicillin interactions (68) Amoxicillin drug information
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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:

Venlafaxine + Activated Charcoal American Hellebore Arsenic Cesium Ephedra Grapefruit Lithium Sida Cordifolia + 102 more
Amoxicillin + Activated Charcoal Asarabacca Beer Khat Siberian Cocklebur Wine Aristolochia Ashwagandha + 88 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.