Drug & supplement interaction

Clubmoss + Phenylephrine, Tropicamide

Phenylephrine, Tropicamide brand name: Mydcombi.

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

Clubmoss has a moderate interaction with Phenylephrine, Tropicamide. Evidence from in vitro research suggests that clubmoss extract can inhibit acetylcholinesterase activity.

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

Clubmoss and Phenylephrine, Tropicamide

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

Moderate

ANTICHOLINERGIC DRUGS

Why this applies to Phenylephrine, Tropicamide

Phenylephrine, Tropicamide falls under ANTICHOLINERGIC DRUGS — the group Clubmoss interacts with.

Evidence from in vitro research suggests that clubmoss extract can inhibit acetylcholinesterase activity. Theoretically, concurrent use of anticholinergic drugs and clubmoss might decrease the effectiveness of club moss or the anticholinergic agent. Some anticholinergic drugs include atropine, benztropine (Cogentin), biperiden (Akineton), procyclidine (Kemadrin), and trihexyphenidyl (Artane).
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

Mydcombi eye drops combine phenylephrine and tropicamide to dilate your pupils, usually for an eye exam. The tropicamide part works by blocking acetylcholine, which relaxes the muscles that control your pupil and lets it open up. Here's the wrinkle with clubmoss: in test-tube studies, it seems to do the opposite by boosting acetylcholine levels. So in theory, the two could work against each other, and your pupils might not dilate as fully or stay dilated as long.

I want to be honest that this is very weak, theoretical evidence based only on lab research, not real people. Since these drops are used briefly in a clinic, it's unlikely to be a big deal. Still, it's worth mentioning clubmoss to your eye doctor or pharmacist before your appointment.

Contact Dr. Brian directly if you have additional questions on this interaction
References
  1. Orhan, I., Terzioglu, S., and Sener, B. Alpha-onocerin: an acetylcholinesterase inhibitor from Lycopodium clavatum. Planta Med. 2003;69(3):265-267.

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

Clubmoss Also Interacts With Other Medications

Clubmoss has 218 moderate known drug interactions in our database — the Phenylephrine, Tropicamide one above is one of them. If you take anything else, check it against the full list below.

Moderate 218 No known interaction 2,612 (incl. Phenylephrine, Tropicamide)
Taking anything else?

Check Another of Your Medications Against Clubmoss

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

Everything else you take

See Every Supplement That Interacts With Phenylephrine, Tropicamide

This page covers Clubmoss only. If you take other supplements — a multivitamin, a sleep aid, something for joints — the Phenylephrine, Tropicamide page lists 34 supplements it has a documented interaction with, worst first, each one explained.

The most serious there right now: Henbane (major), Scopolia (major), Angel's Trumpet (moderate), Bacopa (moderate) and Belladonna (moderate).

By severity: 2 major · 29 moderate · 3 minor.

From our pharmacist’s overview on the Phenylephrine, Tropicamide page

“Mydcombi, the phenylephrine and tropicamide spray used to dilate pupils for eye exams, seems like a one-time thing, but enough of it reaches the bloodstream to matter, and the 34 supplement ingredients on this list call for real care before your appointment. Thirty of them act on tropicamide's anticholinergic side, either piling on its…”

Reviewed by 2 · Jul 18, 2026

Open the Phenylephrine, Tropicamide interaction page

How much people look this up

Where Clubmoss and Phenylephrine, Tropicamide 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 Clubmoss
Top half

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

29 days ago today
Medication Phenylephrine, Tropicamide
Top 25%

#414 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 Clubmoss

What is Clubmoss?

Clubmoss
  • Bladder and kidney complaints
  • Digestive upset
  • Skin irritation and chafing
  • Respiratory problems
  • Used in homeopathy

Clubmoss (Lycopodium clavatum) is a primitive plant with a long history in folk medicine and homeopathy, but there is very little reliable human research to show it works for any health condition. It contains potentially toxic alkaloids, so it should be used with great caution, and people who are pregnant or breastfeeding should avoid it. Talk with a pharmacist or doctor before trying it.

Read the full Clubmoss monograph & all interactions
Keep checking

Other Drugs & Clubmoss

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

0Major
218Moderate
0Minor
2,611No known interaction
218 Moderate 2,611 No interaction
Moderate

218 interactions

Showing 60 of 218 moderate interactions — see all 218 on the Clubmoss page.

No interaction 2,611 drugs checked — show the list

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

Showing the 60 most looked-up of 2,611 medications checked with no known interaction — see the full Clubmoss list.

See the full Clubmoss interactions page
See every supplement checked against Phenylephrine, Tropicamide, 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
Clubmoss monograph › Uses, safety, and every drug interaction in one place Phenylephrine, Tropicamide supplement interactions › Every supplement checked against Phenylephrine, Tropicamide, ranked by severity 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 Clubmoss and Phenylephrine, Tropicamide Together: Common Questions

Can you take Clubmoss with Phenylephrine, Tropicamide?
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 Clubmoss and Phenylephrine, Tropicamide 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 Phenylephrine, Tropicamide and Clubmoss?

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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.