Drug & supplement interaction

Vitex Agnus-castus + Modafinil

Modafinil brand names: Provigil, Sparlon, Alertec.

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

Vitex Agnus-castus has a moderate interaction with Modafinil. Theoretically, vitex agnus-castus could interfere with dopamine agonists.

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

Vitex Agnus-castus and Modafinil

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

Moderate

DOPAMINE AGONISTS

Why this applies to Modafinil

Modafinil falls under DOPAMINE AGONISTS — the group Vitex Agnus-castus interacts with.

Theoretically, vitex agnus-castus could interfere with dopamine agonists.
Vitex agnus-castus might potentiate the actions of dopaminergic agonists due to possible dopaminergic effects.
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 idea behind pairing chasteberry (Vitex) with modafinil. Lab and animal studies hint that Vitex may nudge up dopamine activity in the brain. Since modafinil also works partly by boosting dopamine signaling to keep you awake and alert, the thought is that combining the two could add to each other's effects.

If that happened, you might notice more of modafinil's typical reactions, like jitteriness, headache, trouble sleeping, a racing heart, or feeling anxious or wired. I want to be honest, though: this is a theoretical concern based only on test-tube and animal data, not real patient cases, so the actual risk for most people is likely small. Modafinil is not a prodrug, so this is about overlapping effects rather than changing how it's broken down. If you want to use both, just run it by your pharmacist or doctor first.

Contact Dr. Brian directly if you have additional questions on this interaction
References
  1. Meier B, Berger D, Hoberg E, et al. Pharmacological activities of Vitex agnus-castus extracts in vitro. Phytomedicine 2000;7:373-81. PubMed

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

Vitex Agnus-castus Also Interacts With Other Medications

Vitex Agnus-castus has 120 moderate known drug interactions in our database — the Modafinil one above is one of them. If you take anything else, check it against the full list below.

Moderate 120 No known interaction 2,710 (incl. Modafinil)
Taking anything else?

Check Another of Your Medications Against Vitex Agnus-castus

Covers the 2,830 medications we’ve checked against Vitex Agnus-castus. Pick one to open its full report.

Everything else you take

See Every Supplement That Interacts With Modafinil

This page covers Vitex Agnus-castus only. If you take other supplements — a multivitamin, a sleep aid, something for joints — the Modafinil page lists 197 supplements it has a documented interaction with, worst first, each one explained.

The most serious there right now: Activated Charcoal (major), Adrafinil (major), Ephedra (major), Grapefruit (major) and Peyote (major).

By severity: 8 major · 150 moderate · 39 minor.

From our pharmacist’s overview on the Modafinil page

“Of the 197 supplements and herbs flagged for modafinil (Provigil, Alertec), eight carry a major rating, and those deserve real caution. Most of the rest fall into two themes.”

Reviewed by 2 · Jul 18, 2026

Open the Modafinil interaction page

One more smart check

Taking Vitex Agnus-castus as Part of a Dietary Supplement Product? Check It for Interactions

We hold 45 real supplement products containing Vitex Agnus-castus, each one broken down to its full ingredient list — and combination products often carry several ingredients besides Vitex Agnus-castus. Your product may carry other ingredients that interact with Modafinil too, on top of Vitex Agnus-castus — 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 Vitex Agnus-castus and Modafinil 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 Vitex Agnus-castus
Top half

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

29 days ago today
Medication Modafinil
Top half

#1,225 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 Vitex Agnus-castus

What is Vitex Agnus-castus?

Vitex Agnus-castus
  • Premenstrual syndrome (PMS)
  • Irregular or absent menstrual periods
  • Cyclical breast pain (mastalgia)
  • Menopause symptoms
  • Fertility support

Vitex (chasteberry) is an herbal remedy most often used for PMS and menstrual cycle problems, and the strongest evidence is for easing some PMS symptoms. It is generally well tolerated by many adults, but it can affect hormone-related processes, so anyone who is pregnant, breastfeeding, or has a hormone-sensitive condition should talk with a healthcare professional first.

Read the full Vitex Agnus-castus monograph & all interactions
Medication

About Modafinil

What Is Modafinil Used For?

Brand names: Provigil, Sparlon, Alertec

Modafinil (also sold as Provigil) is used to improve wakefulness in adults who experience excessive sleepiness due to narcolepsy, obstructive sleep apnea (OSA), or shift work disorder (SWD).

In OSA, modafinil treats the sleepiness — not the underlying airway obstruction itself. It is used alongside standard treatments such as CPAP (a breathing device worn during sleep), not as a replacement for them. If CPAP is appropriate for you, your doctor will want you to use it consistently even while taking modafinil.

See full Modafinil drug information
Keep checking

Other Drugs & Vitex Agnus-castus

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

0Major
120Moderate
0Minor
2,709No known interaction
120 Moderate 2,709 No interaction
Moderate

120 interactions

Showing 60 of 120 moderate interactions — see all 120 on the Vitex Agnus-castus page.

No interaction 2,709 drugs checked — show the list

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

Showing the 60 most looked-up of 2,709 medications checked with no known interaction — see the full Vitex Agnus-castus list.

See the full Vitex Agnus-castus interactions page
See every supplement checked against Modafinil, 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
Vitex Agnus-castus monograph › Uses, safety, and every drug interaction in one place Modafinil supplement interactions › Every supplement checked against Modafinil, ranked by severity Modafinil 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 Vitex Agnus-castus and Modafinil Together: Common Questions

Can you take Vitex Agnus-castus with Modafinil?
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.
How serious is the Vitex Agnus-castus and Modafinil 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 Modafinil and Vitex Agnus-castus?

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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.