Drug & supplement interaction

Valerian + Dextromethorphan, Guaifenesin, Phenylephrine

Dextromethorphan, Guaifenesin, Phenylephrine brand names: Albatussin Sr, Giltuss.

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

Dextromethorphan, Guaifenesin, Phenylephrine falls into 2 drug categories that Valerian can interact with; the most serious is rated minor. Valerian does not seem to have a clinically relevant effect on levels of drugs metabolized by CYP2D6.

Read the full interaction report
SeverityMinor
LikelihoodUnlikely
Interactions2
EvidenceB
What do Severity, Likelihood & Evidence mean?
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Interaction report

Valerian and Dextromethorphan, Guaifenesin, Phenylephrine

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

Why Are There 2 Interactions?

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

Minor

CYTOCHROME P450 2D6 (CYP2D6) SUBSTRATES

1 of 2

Why this applies to Dextromethorphan, Guaifenesin, Phenylephrine

Dextromethorphan, Guaifenesin, Phenylephrine falls under CYTOCHROME P450 2D6 (CYP2D6) SUBSTRATES — the group Valerian interacts with.

Valerian does not seem to have a clinically relevant effect on levels of drugs metabolized by CYP2D6.
Although some in vitro evidence suggests that valerian affects CYP2D6, clinical pharmacokinetic (PK) studies show that valerian is unlikely to affect the CYP2D6 enzyme. In one PK study, taking valerian 1000 mg (providing about 11 mg valerenic acid) nightly for 14 days did not affect the metabolism of dextromethorphan, a CYP2D6 substrate. In another PK study, taking valerian 125 mg three times daily for 28 days did not affect metabolism of debrisoquine, an accepted CYP2D6 probe-substrate.
Severity Minor Likelihood Unlikely Evidence B

Interaction has been demonstrated in animal or in lab research but has been shown not to occur in humans..

Dr. Brian Staiger, PharmD, BCPS
Dr. Brian Staiger explains PharmD, Clinical Pharmacist

Good news here. People often worry that mixing valerian with a cough and cold combo like this one (the dextromethorphan, guaifenesin, and phenylephrine in Giltuss or Albatussin) could cause a problem. On paper, valerian was thought to maybe slow down an enzyme called CYP2D6, which helps clear dextromethorphan. But actual studies in people, including one that paired valerian directly with dextromethorphan, found no meaningful change in how the drug was handled.

So this interaction is rated minor and unlikely. I wouldn't expect extra drowsiness, dizziness, or any buildup of dextromethorphan from the valerian itself. That said, valerian and these cold medicines can each make you a bit sleepy on their own, so go easy and check with your pharmacist if you feel unusually groggy.

Contact Dr. Brian directly if you have additional questions on this interaction
References
  1. Donovan JL, DeVane CL, Chavin KD, et al. Multiple night-time doses of valerian (Valeriana officinalis) had minimal effects on CYP3A4 activity and no effect on CYP2D6 activity in healthy volunteers. Drug Metab Dispos 2004;32:1333-6. PubMed
  2. Gurley BJ, Gardner SF, Hubbard MA, et al. In vivo effects of goldenseal, kava kava, black cohosh, and valerian on human cytochrome P450 1A2, 2D6, 2E1, and 3A4/5 phenotypes. Clin Pharmacol Ther 2005;77:415-26. PubMed
  3. Hellum BH, Nilsen OG. The in vitro inhibitory potential of trade herbal products on human CYP2D6-mediated metabolism and the influence of ethanol. Basic Clin Pharmacol Toxicol. 2007 Nov;101:350-8.
  4. Hellum BH, Hu Z, Nilsen OG. The induction of CYP1A2, CYP2D6 and CYP3A4 by six trade herbal products in cultured primary human hepatocytes. Basic Clin Pharmacol Toxicol. 2007 Jan;100:23-30. PubMed
Minor

CYTOCHROME P450 3A4 (CYP3A4) SUBSTRATES

2 of 2

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

Valerian does not seem to have a clinically relevant effect on levels of drugs metabolized by CYP3A4.
Although some in vitro evidence suggests that valerian extract might inhibit or induce CYP3A4, clinical pharmacokinetic (PK) studies show that valerian does not have a clinically significant effect on the CYP3A4 enzyme. In one PK study, taking valerian 125 mg three times daily for 28 days did not affect metabolism of midazolam, an accepted CYP3A4 probe-substrate. In another PK study, taking valerian 1000 mg (providing about 11 mg valerenic acid) nightly for 14 days modestly increases levels of alprazolam, a CYP3A4 substrate, suggesting mild inhibition of CYP3A4. However, this mild inhibition is unlikely to be clinically relevant.
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

Good news here: pairing valerian with this cough and cold combo (dextromethorphan, guaifenesin, and phenylephrine) isn't likely to cause a meaningful problem. While lab tests once hinted that valerian might tweak a liver enzyme called CYP3A4 that helps process some of these ingredients, the actual human studies showed only a tiny effect, not enough to matter in real life.

The one thing I'd gently mention is overlap in feeling drowsy. Valerian is taken to calm you and help with sleep, and dextromethorphan can already make some folks a little sleepy or foggy. Together you might just feel a bit more tired than usual. If you're on other sedating medicines or you ever notice anything unusual, check in with your pharmacist or doctor first.

Contact Dr. Brian directly if you have additional questions on this interaction
References
  1. Budzinski JW, Foster BC, Vandenhoek S, Arnason JT. An in vitro evaluation of human cytochrome P450 3A4 inhibition by selected commercial herbal extracts and tinctures. Phytomedicine 2000;7:273-82. PubMed
  2. Lefebvre T, Foster BC, Drouin CE, et al. In vitro activity of commercial valerian root extracts against human cytochrome P450 3A4. J Pharm Pharmaceut Sci 2004;7:265-73.
  3. Donovan JL, DeVane CL, Chavin KD, et al. Multiple night-time doses of valerian (Valeriana officinalis) had minimal effects on CYP3A4 activity and no effect on CYP2D6 activity in healthy volunteers. Drug Metab Dispos 2004;32:1333-6. PubMed
  4. Gurley BJ, Gardner SF, Hubbard MA, et al. In vivo effects of goldenseal, kava kava, black cohosh, and valerian on human cytochrome P450 1A2, 2D6, 2E1, and 3A4/5 phenotypes. Clin Pharmacol Ther 2005;77:415-26. PubMed
  5. Hellum BH, Hu Z, Nilsen OG. The induction of CYP1A2, CYP2D6 and CYP3A4 by six trade herbal products in cultured primary human hepatocytes. Basic Clin Pharmacol Toxicol. 2007 Jan;100:23-30. 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

Valerian Also Interacts With Other Medications

Valerian has 338 moderate, 563 minor known drug interactions in our database — the Dextromethorphan, Guaifenesin, Phenylephrine one above is among them. If you take anything else, check it against the full list below.

Moderate 338 Minor 563 No known interaction 1,929 (incl. Dextromethorphan, Guaifenesin, Phenylephrine)
Taking anything else?

Check Another of Your Medications Against Valerian

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

From our Q&A

Questions About Valerian or Dextromethorphan, Guaifenesin, Phenylephrine

These are real questions from readers, answered by the pharmacists at HelloPharmacist — written by a person, not generated from a database. Each one covers Valerian or Dextromethorphan, Guaifenesin, Phenylephrine, not necessarily both, but if one is close to what you were about to ask it will usually go further than a database entry can:

Not quite your question? Ask our pharmacists directly — it is free, there is no account required, and answers usually come back within 24 hours.

Everything else you take

See Every Supplement That Interacts With Dextromethorphan, Guaifenesin, Phenylephrine

This page covers Valerian only. If you take other supplements — a multivitamin, a sleep aid, something for joints — the Dextromethorphan, Guaifenesin, Phenylephrine 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, Guaifenesin, Phenylephrine page

“A combination cough medicine like dextromethorphan, guaifenesin, and phenylephrine (Albatussin Sr, Giltuss) deserves real care around supplements, not casual mixing. Of the 197 ingredients with an interaction on file, 8 carry a major rating, and those are the ones to understand first.”

Reviewed by 2 · Jul 18, 2026

Open the Dextromethorphan, Guaifenesin, Phenylephrine interaction page

One more smart check

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

We hold 2,185 real supplement products containing Valerian, each one broken down to its full ingredient list — and combination products often carry several ingredients besides Valerian. Your product may carry other ingredients that interact with Dextromethorphan, Guaifenesin, Phenylephrine too, on top of Valerian — 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 Valerian and Dextromethorphan, Guaifenesin, 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 Valerian
Top 10%

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

29 days ago today
Medication Dextromethorphan, Guaifenesin, Phenylephrine
Steady interest

#1,700 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 Valerian

What is Valerian?

Valerian
  • Insomnia and poor sleep
  • Anxiety and stress
  • Restlessness
  • Muscle tension or cramps
  • Menstrual discomfort

Valerian is an herb whose root is widely used as a natural sleep aid and for calming nerves. The evidence is mixed and often weak, so it may help some people sleep but does not work reliably for everyone. It is generally well tolerated for short-term use, but talk to your pharmacist or doctor before starting it.

Read the full Valerian monograph & all interactions
Keep checking

Other Drugs & Valerian

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

0Major
338Moderate
563Minor
1,928No known interaction
338 Moderate 563 Minor 1,928 No interaction
Moderate

338 interactions

Showing 60 of 338 moderate interactions — see all 338 on the Valerian page.

Minor

563 interactions

Showing 60 of 563 minor interactions — see all 563 on the Valerian page.

No interaction 1,928 drugs checked — show the list

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

Showing the 60 most looked-up of 1,928 medications checked with no known interaction — see the full Valerian list.

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

Can you take Valerian with Dextromethorphan, Guaifenesin, 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.
Why are there 2 interactions listed for Valerian and Dextromethorphan, Guaifenesin, Phenylephrine?
Dextromethorphan, Guaifenesin, Phenylephrine belongs to more than one drug category, and Valerian 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 Valerian and Dextromethorphan, Guaifenesin, 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

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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.