Drug & supplement interaction

Oleander + Erythromycin

Erythromycin brand names: Erythro S, PCE, E-Mycin, Erythro-ES, EryPed Chewable, and others.

Major Interaction
Medically reviewed by · Updated October 2026
The bottom line Major

Oleander has a major interaction with Erythromycin. Theoretically, macrolide antibiotics may increase the risk of oleander toxicity.

Read the full interaction report
SeverityMajor
LikelihoodProbable
EvidenceD
What do Severity, Likelihood & Evidence mean?
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Interaction report

Oleander and Erythromycin

Here is the interaction we found between these two, with the evidence behind it.

Major

MACROLIDE ANTIBIOTICS

Why this applies to Erythromycin

Erythromycin falls under MACROLIDE ANTIBIOTICS — the group Oleander interacts with.

Theoretically, macrolide antibiotics may increase the risk of oleander toxicity.
Macrolide antibiotics reduce levels of bacteria in the gut that break down digoxin to inactive metabolites, increasing digoxin bioavailability. Theoretically, this same process could increase the bioavailability of cardiac glycosides in oleander, increasing its toxicity.
Severity Major Likelihood Probable Evidence D

Interaction has not been documented in well-controlled studies, however, the interaction has been demonstrated in some small human studies or in controlled animal studies in conjunction with multiple case reports..

Dr. Brian Staiger, PharmD, BCPS
Dr. Brian Staiger explains PharmD, Clinical Pharmacist

First things first: oleander is genuinely poisonous, and I'd urge you not to take it at all. But here's the specific concern when you pair it with erythromycin. Oleander contains heart-acting chemicals (cardiac glycosides) very similar to digoxin. Erythromycin can knock down certain gut bacteria that normally break these compounds down, so more of the oleander toxin may end up in your bloodstream.

The worry is that this could raise oleander's toxic effects, things like a dangerously slow or irregular heartbeat, nausea, and vomiting. I'll be honest, this is theoretical and based on how the drugs behave, not on hard human studies. Still, with something as risky as oleander, please don't combine them. Talk with your pharmacist or doctor first.

Contact Dr. Brian directly if you have additional questions on this interaction
References
  1. Ellenhorn MJ, et al. Ellenhorn's Medical Toxicology: Diagnoses and Treatment of Human Poisoning. 2nd ed. Baltimore, MD: Williams & Wilkins, 1997.

What These Ratings Mean

Every interaction above is graded three ways — here’s the key to each label.

Severity how clinically significant the interaction is
Major

Clinically significant. Avoid the combination, or use only under close professional supervision.

Moderate

Usually worth avoiding or managing — may need monitoring, a dose change, or timing apart.

Minor

Generally not serious. Be aware of it and mention it to your pharmacist.

Likelihood how strong the evidence is that the interaction actually happens in people
  • LikelyWell-controlled human studies have demonstrated the likely existence of this interaction.
  • ProbableInteraction has not been documented in well-controlled studies, however, the interaction has been demonstrated in some small human studies or in controlled animal studies in conjunction with multiple case reports.
  • PossibleInteraction has been documented in animal or in lab research, or the interaction has been documented in humans but is limited to case reports or conflicting clinical research exists.
  • UnlikelyInteraction has been demonstrated in animal or in lab research but has been shown not to occur in humans.
Evidence the quality of the studies behind the rating (graded A–D)
  • AHigh-quality meta-analysis (quantitative systematic review).
  • BCase-control study.
  • CConsensus.
  • DAnecdotal evidence.

These ratings are for information only. Never start, stop, or otherwise change your therapy before speaking with your provider.

Keep it in perspective

Oleander Also Interacts With Other Medications

Oleander has 132 major, 23 moderate known drug interactions in our database — the Erythromycin one above is one of them. If you take anything else, check it against the full list below.

Major 132 Moderate 23 No known interaction 2,675 (incl. Erythromycin)
Taking anything else?

Check Another of Your Medications Against Oleander

Covers the 2,830 medications we’ve checked against Oleander. Pick one to open its full report.

From our Q&A

Questions About Oleander or Erythromycin

These are real questions from readers, answered by the pharmacists at HelloPharmacist — written by a person, not generated from a database. Each one covers Oleander or Erythromycin, not necessarily both, but if one is close to what you were about to ask it will usually go further than a database entry can:

Not quite your question? Ask our pharmacists directly — it is free, there is no account required, and answers usually come back within 24 hours.

Everything else you take

See Every Supplement That Interacts With Erythromycin

This page covers Oleander only. If you take other supplements — a multivitamin, a sleep aid, something for joints — the Erythromycin page lists 204 supplements it has a documented interaction with, worst first, each one explained.

The most serious there right now: Activated Charcoal (major), American Hellebore (major), Arsenic (major), Beer (major) and Cesium (major).

By severity: 11 major · 153 moderate · 40 minor.

From our pharmacist’s overview on the Erythromycin page

“Erythromycin calls for more supplement caution than most antibiotics, and the reason is one liver enzyme, CYP3A4. Erythromycin both blocks that enzyme and is broken down by it, so grapefruit can push erythromycin levels up while St.”

Reviewed by 2 · Jul 18, 2026

Open the Erythromycin interaction page

How much people look this up

Where Oleander and Erythromycin Sit Against Everything Else

Out of every supplement and medication people look up on HelloPharmacist, here is where these two land this week — and which way each has been moving.

Supplement Oleander
Top half

#710 of 1,452 supplements looked up here in the last 7 days

29 days ago today
Medication Erythromycin
Steady interest

#1,623 of 2,830 medications looked up here in the last 7 days

29 days ago today

Position among everything looked up on this site, not a measure of how commonly either one is used or how important it is. A supplement can climb this list because of a news story. It counts every request to the page, automated ones included, and nothing here identifies anyone.

Supplement

About Oleander

What is Oleander?

  • Heart failure (traditional)
  • Cancer (investigational)
  • Skin conditions
  • Asthma (folk use)
  • Pain relief (folk use)

Oleander is a highly poisonous ornamental plant, and every part of it can cause life-threatening heart and nervous system effects, even in small amounts. There is no proven safe dose for self-use, and serious poisonings and deaths have occurred from teas, extracts, and accidental ingestion. We strongly advise against using oleander as a supplement.

Read the full Oleander monograph & all interactions
Medication

About Erythromycin

What Is Erythromycin Used For?

Brand names: Erythro S, PCE, E-Mycin, Erythro-ES, EryPed Chewable, Eryc, Ery-Tab, Rythro Enca, Erythro E-C, Erythro Base, Ilosone, Ilotycin

Erythromycin treats infections caused by susceptible bacteria. The oral products (delayed-release tablets, tablets and suspensions) are labeled for mild to moderate upper respiratory tract infections caused by Streptococcus pyogenes, Streptococcus pneumoniae and Haemophilus influenzae. For H. influenzae, it is used together with adequate doses of sulfonamides.

Erythromycin lactobionate injection (Erythrocin Lactobionate and other lactobionate products) is used for similar infections, including lower respiratory tract infections, when oral treatment is not possible or when the infection needs high blood levels right away. Topical erythromycin 2% solution, Ery 2% pads and Spotex gel are used on the skin to treat acne vulgaris.

See full Erythromycin drug information
Keep checking

Other Drugs & Oleander

Browse every other medication we’ve checked against Oleander — both the ones with a known interaction and the ones without. Select any drug for the full detail.

132Major
23Moderate
0Minor
2,674No known interaction
132 Major 23 Moderate 2,674 No interaction
Major

132 interactions

Showing 60 of 132 major interactions — see all 132 on the Oleander page.

Moderate

23 interactions

No interaction 2,674 drugs checked — show the list

We also checked Oleander against these medications and found no known interaction in our sources. Open any page to confirm.

Showing the 60 most looked-up of 2,674 medications checked with no known interaction — see the full Oleander list.

See the full Oleander interactions page
See every supplement checked against Erythromycin, ranked by severity
Sources

Sources & How We Checked

Interaction details are evidence-graded and sourced from the Natural Medicines database. The medication overview comes from MedlinePlus.

Content is written and reviewed by licensed HelloPharmacist pharmacists. See our data sources and editorial standards for how this information is built and checked.

Parts of this content are provided by the Therapeutic Research Center, LLC.

DISCLAIMER: Currently this does not check for drug-drug interactions. This is not an all-inclusive comprehensive list of potential interactions and is for informational purposes only. Not all interactions are known or well-reported in the scientific literature, and new interactions are continually being reported. Input is needed from a qualified healthcare provider including a pharmacist before starting any therapy. Application of clinical judgment is necessary.

© 2021 Therapeutic Research Center, LLC

Keep exploring
Oleander monograph › Uses, safety, and every drug interaction in one place Erythromycin supplement interactions › Every supplement checked against Erythromycin, ranked by severity Erythromycin drug information › The full plain-English guide to this medication Supplement interaction checker › Check any supplement or product against your medications Browse medications A–Z › Every drug we've checked against herbs & supplements Ask a pharmacist › Free, personal answer from our licensed team
Pharmacist Counseling Corner

Taking Oleander and Erythromycin Together: Common Questions

Can you take Oleander with Erythromycin?
This is rated a major interaction, so the combination is best avoided unless your doctor or pharmacist has specifically told you otherwise. Read the full details on this page and confirm with your pharmacist before combining them.
How serious is the Oleander and Erythromycin interaction?
We rate it Major. This is a clinically significant combination that is generally best avoided, or used only under the direct supervision of your physician or pharmacist.

Written and reviewed by the HelloPharmacist editorial staff. Our editorial policy

Still Have a Question About Erythromycin and Oleander?

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This information is for education only and is not a substitute for professional medical advice. Always check with your pharmacist or doctor before starting, stopping, or combining supplements and medications.