Drug & supplement interaction

Boswellia Serrata + Dextromethorphan HBr, Phenylephrine HCl

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

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

Dextromethorphan HBr, Phenylephrine HCl falls into 2 drug categories that Boswellia Serrata can interact with; the most serious is rated moderate. Theoretically, Boswellia serrata might increase the levels of CYP2D6 substrates.

Read the full interaction report
SeverityModerate
LikelihoodPossible
Interactions2
EvidenceD
What do Severity, Likelihood & Evidence mean?
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Interaction report

Boswellia Serrata and Dextromethorphan HBr, Phenylephrine HCl

These two interact in 2 distinct ways. Each one is explained separately below.

Why Are There 2 Interactions?

Boswellia Serrata interacts with whole categories of medication. Dextromethorphan HBr, Phenylephrine HCl falls into 2 of those categories, so it can interact with Boswellia Serrata in 2 different ways. We’ve listed each one below — your overall risk is driven by the most serious of them (Moderate).

Moderate

CYTOCHROME P450 2D6 (CYP2D6) SUBSTRATES

1 of 2

Why this applies to Dextromethorphan HBr, Phenylephrine HCl

Dextromethorphan HBr, Phenylephrine HCl falls under CYTOCHROME P450 2D6 (CYP2D6) SUBSTRATES — the group Boswellia Serrata interacts with.

Theoretically, Boswellia serrata might increase the levels of CYP2D6 substrates.
In vitro research shows that Boswellia serrata gum resin inhibits CYP2D6 enzymes.
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 gist: the dextromethorphan in this cough and congestion product is cleared from your body mainly by a liver enzyme called CYP2D6. In lab testing, boswellic acids appear to slow that enzyme down. If that happens in real life, dextromethorphan could build up a bit and lead to stronger effects like drowsiness, dizziness, or feeling foggy or lightheaded.

I want to be honest about how soft this evidence is. It comes only from test-tube studies, not from people, so it may not amount to much in everyday use, especially with short-term cough relief. The phenylephrine piece is not really involved here. If you take boswellia regularly, just mention it to your pharmacist or doctor before pairing it with this product.

Contact Dr. Brian directly if you have additional questions on this interaction
References
  1. Frank A, Unger M. Analysis of frankincense from various Boswellia species with inhibitory activity on human drug metabolising cytochrome P450 enzymes using liquid chromatography mass spectrometry after automated on-line extraction. J Chromatogr A 2006;111 PubMed
Moderate

CYTOCHROME P450 3A4 (CYP3A4) SUBSTRATES

2 of 2

Dextromethorphan HBr, Phenylephrine HCl also falls under CYTOCHROME P450 3A4 (CYP3A4) SUBSTRATES.

Theoretically, Boswellia serrata might increase or decrease the levels and clinical effects of CYP3A4 substrates.
In vitro research shows that Boswellia serrata gum resin inhibits CYP3A4 enzymes. Other in vitro research shows that Boswellia serrata extract inhibits CYP3A4 enzymes at most concentrations, although it may modestly induce enzyme activity at low concentrations.
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 gist with Vicks Formula 44D, which pairs dextromethorphan (the cough suppressant) with phenylephrine (the decongestant). Lab studies suggest boswellia may slow down a liver enzyme called CYP3A4, one of the pathways that helps break dextromethorphan down. If that clearing slows, a little more dextromethorphan could linger in your system, which might mean more drowsiness, dizziness, or feeling foggy than usual.

I want to be honest: this is purely theoretical, based on test-tube research, not real people taking these together. For most folks using this for a short cold, it's unlikely to cause trouble. Still, if you take boswellia regularly or feel extra groggy, mention it to your pharmacist or doctor before combining them.

Contact Dr. Brian directly if you have additional questions on this interaction
References
  1. Frank A, Unger M. Analysis of frankincense from various Boswellia species with inhibitory activity on human drug metabolising cytochrome P450 enzymes using liquid chromatography mass spectrometry after automated on-line extraction. J Chromatogr A 2006;111 PubMed
  2. 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

Boswellia Serrata Also Interacts With Other Medications

Boswellia Serrata has 951 moderate known drug interactions in our database — the Dextromethorphan HBr, Phenylephrine HCl one above is among them. If you take anything else, check it against the full list below.

Moderate 951 No known interaction 1,879 (incl. Dextromethorphan HBr, Phenylephrine HCl)
Taking anything else?

Check Another of Your Medications Against Boswellia Serrata

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

Everything else you take

See Every Supplement That Interacts With Dextromethorphan HBr, Phenylephrine HCl

This page covers Boswellia Serrata 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 Boswellia Serrata as Part of a Dietary Supplement Product? Check It for Interactions

We hold 1,914 real supplement products containing Boswellia Serrata, each one broken down to its full ingredient list — and combination products often carry several ingredients besides Boswellia Serrata. Your product may carry other ingredients that interact with Dextromethorphan HBr, Phenylephrine HCl too, on top of Boswellia Serrata — 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 Boswellia Serrata 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 Boswellia Serrata
Top 10%

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

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

#2,773 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 Boswellia Serrata

What is Boswellia Serrata?

Boswellia Serrata
  • Osteoarthritis joint pain
  • Rheumatoid arthritis
  • Inflammation
  • Asthma
  • Inflammatory bowel conditions

Boswellia serrata is a tree resin used in traditional medicine, mainly for joint pain and inflammation. Some studies suggest it may help with osteoarthritis symptoms, but the overall evidence is limited and more research is needed. It is generally well tolerated, but you should check with your pharmacist or doctor before using it, especially during pregnancy or breastfeeding.

Read the full Boswellia Serrata monograph & all interactions
Keep checking

Other Drugs & Boswellia Serrata

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

0Major
951Moderate
0Minor
1,878No known interaction
951 Moderate 1,878 No interaction
Moderate

951 interactions

Showing 60 of 951 moderate interactions — see all 951 on the Boswellia Serrata page.

No interaction 1,878 drugs checked — show the list

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

Showing the 60 most looked-up of 1,878 medications checked with no known interaction — see the full Boswellia Serrata list.

See the full Boswellia Serrata 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
Boswellia Serrata 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 Boswellia Serrata and Dextromethorphan HBr, Phenylephrine HCl Together: Common Questions

Can you take Boswellia Serrata with Dextromethorphan HBr, Phenylephrine HCl?
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.
Why are there 2 interactions listed for Boswellia Serrata and Dextromethorphan HBr, Phenylephrine HCl?
Dextromethorphan HBr, Phenylephrine HCl belongs to more than one drug category, and Boswellia Serrata interacts with each of those categories a little differently. We list every one so nothing is missed — your overall risk is driven by the most serious of them.
How serious is the Boswellia Serrata and Dextromethorphan HBr, Phenylephrine HCl 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

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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.