Drug & supplement interaction

Hemp + Dextromethorphan HBr, Phenylephrine HCl

Dextromethorphan HBr, Phenylephrine HCl brand name: Vicks Formula 44D Cough & Head Congestion Relief.

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

Hemp has a minor interaction with Dextromethorphan HBr, Phenylephrine HCl. Theoretically, hemp might decrease the levels and clinical effects of CYP3A4 substrates.

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

Hemp and Dextromethorphan HBr, Phenylephrine HCl

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

Minor

CYTOCHROME P450 3A4 (CYP3A4) SUBSTRATES

Why this applies to Dextromethorphan HBr, Phenylephrine HCl

Dextromethorphan HBr, Phenylephrine HCl falls under CYTOCHROME P450 3A4 (CYP3A4) SUBSTRATES — the group Hemp interacts with.

Theoretically, hemp might decrease the levels and clinical effects of CYP3A4 substrates.
In vitro research shows that hemp induces CYP3A4 enzymes.
Severity Minor 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 short version: this is a very mild, mostly theoretical concern. The cough ingredient in this product, dextromethorphan, is partly handled by a liver enzyme called CYP3A4. Lab studies (not human studies) suggest hemp might nudge that enzyme to work a little faster. In theory, that could clear dextromethorphan slightly quicker and make it a touch less effective at quieting your cough.

In real life, this is unlikely to cause a noticeable problem, especially with hemp seeds or hemp oil eaten as food. The phenylephrine decongestant isn't really affected this way. If your cough just isn't easing up while using both, mention it to your pharmacist, but there's no reason to be alarmed here.

Contact Dr. Brian directly if you have additional questions on this interaction
References
  1. Haron MH, Dale O, Martin K, et al. Evaluation of the Herb-Drug Interaction Potential of Commonly Used Botanicals on the US Market with Regard to PXR- and AhR-Mediated Influences on CYP3A4 and CYP1A2. J Diet Suppl 2022. 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

Hemp Also Interacts With Other Medications

Hemp has 41 moderate, 896 minor known drug interactions in our database — the Dextromethorphan HBr, Phenylephrine HCl one above is one of them. If you take anything else, check it against the full list below.

Moderate 41 Minor 896 No known interaction 1,893 (incl. Dextromethorphan HBr, Phenylephrine HCl)
Taking anything else?

Check Another of Your Medications Against Hemp

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

Everything else you take

See Every Supplement That Interacts With Dextromethorphan HBr, Phenylephrine HCl

This page covers Hemp only. If you take other supplements — a multivitamin, a sleep aid, something for joints — the Dextromethorphan HBr, Phenylephrine HCl page lists 197 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), Lithium (major) and Peyote (major).

By severity: 8 major · 148 moderate · 41 minor.

From our pharmacist’s overview on the Dextromethorphan HBr, Phenylephrine HCl page

“The supplement interactions with Dextromethorphan HBr and Phenylephrine HCl (Vicks Formula 44D) deserve real respect, and the small cluster of major-rated ones should be understood before you reach for the bottle. Phenylephrine is a stimulant-type decongestant, so anything with caffeine (coffee, tea, cola nut) or ephedrine-like herbs s…”

Reviewed by 2 · Jul 18, 2026

Open the Dextromethorphan HBr, Phenylephrine HCl interaction page

One more smart check

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

We hold 720 real supplement products containing Hemp, each one broken down to its full ingredient list — and combination products often carry several ingredients besides Hemp. Your product may carry other ingredients that interact with Dextromethorphan HBr, Phenylephrine HCl too, on top of Hemp — 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 Hemp and Dextromethorphan HBr, Phenylephrine HCl 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 Hemp
Top 25%

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

29 days ago today
Medication Dextromethorphan HBr, Phenylephrine HCl
Steady interest

#2,536 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 Hemp

What is Hemp?

Hemp
  • Plant-based protein source
  • Heart health support
  • Skin and hair health
  • Reducing inflammation
  • General nutrition (omega fatty acids)

Hemp seeds and hemp seed oil are nutritious foods rich in protein, fiber, and healthy omega-3 and omega-6 fatty acids, and they are generally safe for most people as part of the diet. While the nutrition is real, strong human evidence that hemp supplements treat specific medical conditions is limited. Talk with your pharmacist or doctor before using hemp products for a health concern, especially if you are pregnant or breastfeeding.

Read the full Hemp monograph & all interactions
Keep checking

Other Drugs & Hemp

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

0Major
41Moderate
896Minor
1,892No known interaction
41 Moderate 896 Minor 1,892 No interaction
Moderate

41 interactions

Minor

896 interactions

Showing 60 of 896 minor interactions — see all 896 on the Hemp page.

No interaction 1,892 drugs checked — show the list

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

Showing the 60 most looked-up of 1,892 medications checked with no known interaction — see the full Hemp list.

See the full Hemp interactions page
See every supplement checked against Dextromethorphan HBr, Phenylephrine HCl, 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
Hemp monograph › Uses, safety, and every drug interaction in one place Dextromethorphan HBr, Phenylephrine HCl supplement interactions › Every supplement checked against Dextromethorphan HBr, Phenylephrine HCl, 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 Hemp and Dextromethorphan HBr, Phenylephrine HCl Together: Common Questions

Can you take Hemp with Dextromethorphan HBr, Phenylephrine HCl?
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 Hemp and Dextromethorphan HBr, Phenylephrine HCl 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 Dextromethorphan HBr, Phenylephrine HCl and Hemp?

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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.