Drug & supplement interaction

Alpha-gpc + Chlorpheniramine, Methscopolamine, Phenylephrine

Chlorpheniramine, Methscopolamine, Phenylephrine brand names: DA II, Extendryl JR, Dallergy, Extendryl SR, Extendryl Chews, and others.

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

Alpha-gpc has a minor interaction with Chlorpheniramine, Methscopolamine, Phenylephrine. Theoretically, alpha-GPC might decrease the effects of scopolamine.

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

Alpha-gpc and Chlorpheniramine, Methscopolamine, Phenylephrine

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

Minor

SCOPOLAMINE (Transderm Scop)

Theoretically, alpha-GPC might decrease the effects of scopolamine.
A small clinical study shows that alpha-GPC can partially counteract the attention and memory impairment effects caused by scopolamine given intramuscularly. Whether alpha-GPC can decrease the beneficial anti-motion sickness effects of the scopolamine patch (Transderm Scop) is unclear.
Severity Minor Likelihood Possible Evidence B

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 simple version. Your combination product contains methscopolamine, a drying agent in the same family as scopolamine, plus chlorpheniramine. Both of these work partly by quieting acetylcholine, the brain and body messenger. Alpha-GPC does the opposite. It gives your body more raw material to make acetylcholine, so in theory it could nudge against the drying, anti-runny-nose action of methscopolamine.

In plain terms, this is a tug-of-war that might slightly weaken the medicine, not make it dangerous. The evidence is thin and comes from a small study using injected scopolamine, so real-world impact for a pill or chewable like this is uncertain. If your congestion symptoms aren't easing, mention it to your pharmacist or doctor before changing anything.

Contact Dr. Brian directly if you have additional questions on this interaction
References
  1. Canal N, Franceschi M, Alberoni M, et al. Effect of L-alpha-glyceryl-phosphorylcholine on amnesia caused by scopolamine. Int J Clin Pharmacol Ther Toxicol 1991;29:103-7.

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

Alpha-gpc Also Interacts With Other Medications

Alpha-gpc has 15 minor known drug interactions in our database — the Chlorpheniramine, Methscopolamine, Phenylephrine one above is one of them. If you take anything else, check it against the full list below.

Minor 15 No known interaction 2,815 (incl. Chlorpheniramine, Methscopolamine, Phenylephrine)
Taking anything else?

Check Another of Your Medications Against Alpha-gpc

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

Everything else you take

See Every Supplement That Interacts With Chlorpheniramine, Methscopolamine, Phenylephrine

This page covers Alpha-gpc only. If you take other supplements — a multivitamin, a sleep aid, something for joints — the Chlorpheniramine, Methscopolamine, Phenylephrine page lists 230 supplements it has a documented interaction with, worst first, each one explained.

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

By severity: 10 major · 175 moderate · 45 minor.

From our pharmacist’s overview on the Chlorpheniramine, Methscopolamine, Phenylephrine page

“This allergy and congestion combination, Chlorpheniramine, Methscopolamine, and Phenylephrine (Dallergy, Extendryl), has 230 supplement and herbal ingredients on its interaction list, and 10 of them carry major ratings, so this is a list to check carefully rather than skim. The largest group works through the liver enzyme that breaks t…”

Reviewed by 2 · Jul 18, 2026

Open the Chlorpheniramine, Methscopolamine, Phenylephrine interaction page

One more smart check

Taking Alpha-gpc as Part of a Dietary Supplement Product? Check It for Interactions

We hold 1,138 real supplement products containing Alpha-gpc, each one broken down to its full ingredient list — and combination products often carry several ingredients besides Alpha-gpc. Your product may carry other ingredients that interact with Chlorpheniramine, Methscopolamine, Phenylephrine too, on top of Alpha-gpc — 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 Alpha-gpc and Chlorpheniramine, Methscopolamine, Phenylephrine 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 Alpha-gpc
Top 10%

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

29 days ago today
Medication Chlorpheniramine, Methscopolamine, Phenylephrine
Top 25%

#610 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 Alpha-gpc

What is Alpha-gpc?

Alpha-gpc
  • Memory and learning support
  • Age-related cognitive decline
  • Alzheimer's disease and dementia (under study)
  • Athletic and physical performance
  • Source of choline

Alpha-GPC is a choline-containing compound used mainly for memory, brain health, and as a choline source. There is some evidence it may help cognition in people with dementia, but evidence in healthy people is limited. Talk to your pharmacist or doctor before starting it, especially if you take other medicines or have a health condition.

Read the full Alpha-gpc monograph & all interactions
Keep checking

Other Drugs & Alpha-gpc

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

0Major
0Moderate
15Minor
2,814No known interaction
15 Minor 2,814 No interaction
Minor

15 interactions

No interaction 2,814 drugs checked — show the list

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

Showing the 60 most looked-up of 2,814 medications checked with no known interaction — see the full Alpha-gpc list.

See the full Alpha-gpc interactions page
See every supplement checked against Chlorpheniramine, Methscopolamine, Phenylephrine, 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
Alpha-gpc monograph › Uses, safety, and every drug interaction in one place Chlorpheniramine, Methscopolamine, Phenylephrine supplement interactions › Every supplement checked against Chlorpheniramine, Methscopolamine, Phenylephrine, 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 Alpha-gpc and Chlorpheniramine, Methscopolamine, Phenylephrine Together: Common Questions

Can you take Alpha-gpc with Chlorpheniramine, Methscopolamine, Phenylephrine?
There is only a minor interaction, which is usually not serious. Read the full details on this page and confirm with your pharmacist before combining them.
How serious is the Alpha-gpc and Chlorpheniramine, Methscopolamine, Phenylephrine interaction?
We rate it Minor. This interaction is generally not clinically significant, but it remains worth noting and discussing with your pharmacist.

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

Still Have a Question About Chlorpheniramine, Methscopolamine, Phenylephrine and Alpha-gpc?

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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.