Drug & supplement interaction

Marjoram + Pheniramine, Phenylephrine, Phenylpropan, Pyrilamine,

Pheniramine, Phenylephrine, Phenylpropan, Pyrilamine, brand name: Allerstat.

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

Marjoram has a moderate interaction with Pheniramine, Phenylephrine, Phenylpropan, Pyrilamine,. In vitro research suggests that marjoram 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

Marjoram and Pheniramine, Phenylephrine, Phenylpropan, Pyrilamine,

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

Moderate

ANTICHOLINERGIC DRUGS

Why this applies to Pheniramine, Phenylephrine, Phenylpropan, Pyrilamine,

Pheniramine, Phenylephrine, Phenylpropan, Pyrilamine, falls under ANTICHOLINERGIC DRUGS — the group Marjoram interacts with.

In vitro research suggests that marjoram extract can inhibit acetylcholinesterase activity. Theoretically, using marjoram in medicinal amounts along with anticholinergic drugs might decrease the effectiveness of marjoram 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

This combination product (Allerstat) pairs two older antihistamines, pheniramine and pyrilamine, with the decongestant phenylephrine. The antihistamine pieces have a mild drying, or anticholinergic, side to them, which is why they can cause dry mouth, blurry vision, constipation, or drowsiness. Marjoram, in lab dishes, seems to do the opposite: it gently blocks the enzyme that breaks down acetylcholine, nudging things in the anticholinergic direction.

So in theory, concentrated marjoram supplements and these antihistamines could partly cancel each other out, making each work a little less well. Honestly, this is only a test-tube idea, not something proven in people, and ordinary cooking amounts of marjoram are very unlikely to matter. If you regularly use marjoram capsules or oil, just mention it to your pharmacist.

Contact Dr. Brian directly if you have additional questions on this interaction
References
  1. Orhan, I., Kartal, M., Kan, Y., and Sener, B. Activity of essential oils and individual components against acetyl- and butyrylcholinesterase. Z.Naturforsch.C. 2008;63(7-8):547-553.
  2. Chung, Y. K., Heo, H. J., Kim, E. K., Kim, H. K., Huh, T. L., Lim, Y., Kim, S. K., and Shin, D. H. Inhibitory effect of ursolic acid purified from Origanum majorana L on the acetylcholinesterase. Mol.Cells 4-30-2001;11(2):137-143. DOI

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

Marjoram Also Interacts With Other Medications

Marjoram has 337 moderate known drug interactions in our database — the Pheniramine, Phenylephrine, Phenylpropan, Pyrilamine, one above is one of them. If you take anything else, check it against the full list below.

Moderate 337 No known interaction 2,493 (incl. Pheniramine, Phenylephrine, Phenylpropan, Pyrilamine,)
Taking anything else?

Check Another of Your Medications Against Marjoram

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

Everything else you take

See Every Supplement That Interacts With Pheniramine, Phenylephrine, Phenylpropan, Pyrilamine,

This page covers Marjoram only. If you take other supplements — a multivitamin, a sleep aid, something for joints — the Pheniramine, Phenylephrine, Phenylpropan, Pyrilamine, page lists 91 supplements it has a documented interaction with, worst first, each one explained.

The most serious there right now: Activated Charcoal (major), Ephedra (major), Henbane (major), Peyote (major) and Rauvolfia Vomitoria (major).

By severity: 7 major · 69 moderate · 15 minor.

From our pharmacist’s overview on the Pheniramine, Phenylephrine, Phenylpropan, Pyrilamine, page

“Allerstat packs two antihistamines (pheniramine and pyrilamine) alongside two decongestants (phenylephrine and phenylpropanolamine), so supplements can collide with it two ways, and this is a list I would not skim. Seven of the 91 ingredients rate major, and the rest split 69 moderate, 15 minor.”

Reviewed by 2 · Jul 18, 2026

Open the Pheniramine, Phenylephrine, Phenylpropan, Pyrilamine, interaction page

One more smart check

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

We hold 7 real supplement products containing Marjoram, each one broken down to its full ingredient list — and combination products often carry several ingredients besides Marjoram. Your product may carry other ingredients that interact with Pheniramine, Phenylephrine, Phenylpropan, Pyrilamine, too, on top of Marjoram — 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 Marjoram and Pheniramine, Phenylephrine, Phenylpropan, Pyrilamine, 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 Marjoram
Steady interest

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

29 days ago today
Medication Pheniramine, Phenylephrine, Phenylpropan, Pyrilamine,
Top 25%

#415 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 Marjoram

What is Marjoram?

Marjoram
  • Digestive upset
  • Sleep and relaxation
  • Respiratory complaints (cough, congestion)
  • Menstrual discomfort
  • Aromatherapy for stress

Marjoram is a Mediterranean kitchen herb related to oregano that is widely used in food and traditional medicine for digestive, sleep, and respiratory complaints. Most of its health claims rest on traditional use and small lab or animal studies rather than strong human trials. It is generally considered safe as a food, but concentrated supplements and essential oils should be used with caution and avoided in pregnancy.

Read the full Marjoram monograph & all interactions
Keep checking

Other Drugs & Marjoram

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

0Major
337Moderate
0Minor
2,492No known interaction
337 Moderate 2,492 No interaction
Moderate

337 interactions

Showing 60 of 337 moderate interactions — see all 337 on the Marjoram page.

No interaction 2,492 drugs checked — show the list

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

Showing the 60 most looked-up of 2,492 medications checked with no known interaction — see the full Marjoram list.

See the full Marjoram interactions page
See every supplement checked against Pheniramine, Phenylephrine, Phenylpropan, Pyrilamine,, 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
Marjoram monograph › Uses, safety, and every drug interaction in one place Pheniramine, Phenylephrine, Phenylpropan, Pyrilamine, supplement interactions › Every supplement checked against Pheniramine, Phenylephrine, Phenylpropan, Pyrilamine,, 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 Marjoram and Pheniramine, Phenylephrine, Phenylpropan, Pyrilamine, Together: Common Questions

Can you take Marjoram with Pheniramine, Phenylephrine, Phenylpropan, Pyrilamine,?
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 Marjoram and Pheniramine, Phenylephrine, Phenylpropan, Pyrilamine, 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 Pheniramine, Phenylephrine, Phenylpropan, Pyrilamine, and Marjoram?

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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.