Drug & supplement interaction

Lime + 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

Lime has a moderate interaction with Dextromethorphan HBr, Phenylephrine HCl. Animal research shows that phenolics in lime juice inhibit cytochrome P450 3A4.

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

Lime and Dextromethorphan HBr, Phenylephrine HCl

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

Moderate

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 Lime interacts with.

Animal research shows that phenolics in lime juice inhibit cytochrome P450 3A4. This has been demonstrated in rats treated with sildenafil, a CYP3A4 substrate, and high doses of lime juice.
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 your Vicks Formula 44D. The dextromethorphan piece is partly cleared by a liver enzyme called CYP3A4 (it also relies on CYP2D6). Lab and animal studies hint that compounds in lime juice may slow CYP3A4 a little. If that happened in people, dextromethorphan could linger a bit longer, which might mean more drowsiness, dizziness, or a foggy feeling than usual.

That said, this is weak, early evidence from rats given large amounts of lime juice, not humans. A squeeze of lime on your food or in a drink is very unlikely to cause trouble. I'd only pause over concentrated lime extracts. The phenylephrine part isn't really driven by this enzyme. If you take this cough product often, just check with your pharmacist.

Contact Dr. Brian directly if you have additional questions on this interaction
References
  1. Bailey DG, Dresser GK, Bend JR. Bergamottin, lime juice, and red wine as inhibitors of cytochrome P450 3A4 activity: comparison with grapefruit juice. Clin Pharmacol Ther 2003;73:529-37. PubMed
  2. Ademosun AO, Mohammed A, Oboh G, Ajeigbe OF. Influence of lemon (Citrus limon) and lime (Citrus aurantifolia) juices on the erectogenic properties of sildenafil in rats with L-NAME-induced erectile dysfunction. J Food Biochem 2022;46(2):e14074.

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

Lime Also Interacts With Other Medications

Lime has 885 moderate 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 885 No known interaction 1,945 (incl. Dextromethorphan HBr, Phenylephrine HCl)
Taking anything else?

Check Another of Your Medications Against Lime

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

Everything else you take

See Every Supplement That Interacts With Dextromethorphan HBr, Phenylephrine HCl

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

We hold 322 real supplement products containing Lime, each one broken down to its full ingredient list — and combination products often carry several ingredients besides Lime. Your product may carry other ingredients that interact with Dextromethorphan HBr, Phenylephrine HCl too, on top of Lime — 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 Lime 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 Lime
Top 25%

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

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

#2,661 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 Lime

What is Lime?

Lime
  • Source of vitamin C
  • Digestive upset
  • Skin care
  • Mood and aromatherapy
  • Flavoring and food preservation

Lime is a common citrus fruit and a good natural source of vitamin C and plant antioxidants. As a food it is generally safe and enjoyed by most people, but evidence that lime treats any specific health condition is limited. Use the essential oil with care, and check with your pharmacist or doctor before using concentrated lime products for health reasons.

Read the full Lime monograph & all interactions
Keep checking

Other Drugs & Lime

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

0Major
885Moderate
0Minor
1,944No known interaction
885 Moderate 1,944 No interaction
Moderate

885 interactions

Showing 60 of 885 moderate interactions — see all 885 on the Lime page.

No interaction 1,944 drugs checked — show the list

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

Showing the 60 most looked-up of 1,944 medications checked with no known interaction — see the full Lime list.

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

Can you take Lime 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.
How serious is the Lime 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

Still Have a Question About Dextromethorphan HBr, Phenylephrine HCl and Lime?

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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.