Drug & supplement interaction

Adrafinil + Erythromycin Stearate

Erythromycin Stearate brand names: Erythro-S, Erythrocin, Ethril.

Moderate Interaction
Medically reviewed by · Updated September 2026
The bottom line Moderate

Erythromycin Stearate falls into 2 drug categories that Adrafinil can interact with; the most serious is rated moderate. Theoretically, drugs that inhibit CYP3A4 might increase the levels and clinical effects of adrafinil.

Read the full interaction report
SeverityModerate
LikelihoodPossible
Interactions2
EvidenceD
What do Severity, Likelihood & Evidence mean?
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Interaction report

Adrafinil and Erythromycin Stearate

These two interact in 2 distinct ways. Each one is explained separately below.

Why Are There 2 Interactions?

Adrafinil interacts with whole categories of medication. Erythromycin Stearate falls into 2 of those categories, so it can interact with Adrafinil in 2 different ways. We’ve listed each one below — your overall risk is driven by the most serious of them (Moderate).

Moderate

CYTOCHROME P450 3A4 (CYP3A4) INHIBITORS

1 of 2

Why this applies to Erythromycin Stearate

Erythromycin Stearate falls under CYTOCHROME P450 3A4 (CYP3A4) INHIBITORS — the group Adrafinil interacts with.

Theoretically, drugs that inhibit CYP3A4 might increase the levels and clinical effects of adrafinil.
Adrafinil is a precursor to the stimulant prescription drug modafinil. Modafinil is metabolized by CYP3A4.
Severity Moderate Likelihood Possible Evidence D

Interaction 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.

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

Here's the gist: erythromycin can slow down a liver enzyme called CYP3A4. That same enzyme helps clear modafinil, which is what adrafinil turns into once your liver processes it. So if you take both, modafinil may stick around longer and feel stronger than usual. In real life, that could mean more jitteriness, trouble sleeping, a racing heart, headache, or feeling anxious or on edge.

I'll be honest with you, this one is theoretical. It's based on how these drugs work on paper, not on solid studies in people, so it may not happen at all. Still, adrafinil is unregulated and rough on the liver, and erythromycin can be too. Please check with your pharmacist or doctor before pairing them.

Contact Dr. Brian directly if you have additional questions on this interaction
References
  1. Urban AE, Cubala WJ. The role of eugeroics in the treatment of affective disorders. Psychiatr Pol. 2020;54(1):21-33. PubMed
  2. Provigil (modafinil) [package insert]. North Wales, PA: Teva Pharmaceuticals USA, Inc. Published: January 2015. Accessed on: Nov 11, 2022.
Moderate

CYTOCHROME P450 3A4 (CYP3A4) SUBSTRATES

2 of 2

Erythromycin Stearate also falls under CYTOCHROME P450 3A4 (CYP3A4) SUBSTRATES.

Theoretically, adrafanil might reduce levels and clinical effects of CYP3A4 substrates.
Adrafinil is a precursor to the stimulant prescription drug modafinil. Modafinil has been shown to weakly induce CYP3A4 activity.
Severity Moderate Likelihood Possible Evidence D

Interaction 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.

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

Here's the gist for this pairing. Adrafinil turns into modafinil in your body, and modafinil can mildly speed up an enzyme called CYP3A4. Your erythromycin is partly handled by that same enzyme, so in theory, revving it up could clear the antibiotic a little faster and leave you with slightly lower levels in your blood.

If that happens, the worry isn't a scary side effect, it's that the erythromycin might not work quite as well against the infection you're treating. I want to be honest though: this is a theoretical concern based on how the drugs behave, not something proven in real patients. Since you want your antibiotic at full strength, it's worth a quick chat with your pharmacist or doctor before combining them.

Contact Dr. Brian directly if you have additional questions on this interaction
References
  1. Urban AE, Cubala WJ. The role of eugeroics in the treatment of affective disorders. Psychiatr Pol. 2020;54(1):21-33. PubMed
  2. Provigil (modafinil) [package insert]. North Wales, PA: Teva Pharmaceuticals USA, Inc. Published: January 2015. Accessed on: Nov 11, 2022.

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

Adrafinil Also Interacts With Other Medications

Adrafinil has 1 major, 1,055 moderate known drug interactions in our database — the Erythromycin Stearate one above is among them. If you take anything else, check it against the full list below.

Major 1 Moderate 1,055 No known interaction 1,774 (incl. Erythromycin Stearate)
Taking anything else?

Check Another of Your Medications Against Adrafinil

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

From our Q&A

Questions About Adrafinil or Erythromycin Stearate

These are real questions from readers, answered by the pharmacists at HelloPharmacist — written by a person, not generated from a database. Each one covers Adrafinil or Erythromycin Stearate, 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 Stearate

This page covers Adrafinil only. If you take other supplements — a multivitamin, a sleep aid, something for joints — the Erythromycin Stearate 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 Stearate page

“Erythromycin stearate (Erythrocin, Ethril) is an antibiotic that asks for real vigilance around supplements. It blocks the body's main drug-clearing enzyme, so the largest share of this list is herbs whose blood levels can climb while you take it.”

Reviewed by 2 · Jul 18, 2026

Open the Erythromycin Stearate interaction page

One more smart check

Taking Adrafinil as Part of a Dietary Supplement Product? Check It for Interactions

We hold 7 real supplement products containing Adrafinil, each one broken down to its full ingredient list — and combination products often carry several ingredients besides Adrafinil. Your product may carry other ingredients that interact with Erythromycin Stearate too, on top of Adrafinil — and those would not show on this page. Find your product and we’ll check every ingredient on its label:

How much people look this up

Where Adrafinil and Erythromycin Stearate 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 Adrafinil
Steady interest

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

29 days ago today
Medication Erythromycin Stearate
Steady interest

#2,161 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 Adrafinil

What is Adrafinil?

Adrafinil
  • Wakefulness and alertness
  • Fatigue
  • Focus and concentration
  • Cognitive enhancement (nootropic)
  • Daytime sleepiness

Adrafinil is a synthetic compound that the body converts into modafinil, a prescription wakefulness-promoting drug. It is sometimes sold as a nootropic supplement, but it is unregulated, carries real risks (especially to the liver), and is banned in some sports and countries. Talk with a doctor or pharmacist before using it.

Read the full Adrafinil monograph & all interactions
Medication

About Erythromycin

What Is Erythromycin Used For?

Brand names: Erythro-S, Erythrocin, Ethril

Erythromycin treats bacterial infections caused by susceptible organisms. Oral and intravenous forms are used for upper and lower respiratory tract infections, skin and soft-tissue infections, pertussis (whooping cough), Legionnaires' disease, sexually transmitted infections (gonorrhea, syphilis, chlamydia), listeriosis, and other conditions. Erythrocin Lactobionate IV and erythromycin lactobionate injection are specifically for patients who cannot take oral medication or who need rapid, high blood levels due to severe infection — IV therapy should be switched to oral as soon as appropriate.

Erythromycin topical solution 2% and Ery 2% Pads (swabs) are indicated only for the topical treatment of acne vulgaris (acne) and are applied directly to the skin — they are not used for internal infections.

See full Erythromycin drug information
Keep checking

Other Drugs & Adrafinil

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

1Major
1,055Moderate
0Minor
1,773No known interaction
1 Major 1,055 Moderate 1,773 No interaction
Major

1 interaction

Moderate

1,055 interactions

Showing 60 of 1,055 moderate interactions — see all 1,055 on the Adrafinil page.

No interaction 1,773 drugs checked — show the list

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

Showing the 60 most looked-up of 1,773 medications checked with no known interaction — see the full Adrafinil list.

See the full Adrafinil interactions page
See every supplement checked against Erythromycin Stearate, 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
Adrafinil monograph › Uses, safety, and every drug interaction in one place Erythromycin Stearate supplement interactions › Every supplement checked against Erythromycin Stearate, 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 Adrafinil and Erythromycin Stearate Together: Common Questions

Can you take Adrafinil with Erythromycin Stearate?
There is a moderate interaction, so it may be acceptable with monitoring or timing changes — but check with your pharmacist first. Read the full details on this page and confirm with your pharmacist before combining them.
Why are there 2 interactions listed for Adrafinil and Erythromycin Stearate?
Erythromycin Stearate belongs to more than one drug category, and Adrafinil interacts with each of those categories a little differently. We list every one so nothing is missed — your overall risk is driven by the most serious of them.
How serious is the Adrafinil and Erythromycin Stearate interaction?
We rate it Moderate. This combination may require monitoring, a dose adjustment, or separating the times you take each one. Consult your pharmacist before using them together.

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

Still Have a Question About Erythromycin Stearate and Adrafinil?

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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.