Drug & supplement interaction

Baikal Skullcap + Acetaminophen, Chlorpheniramine, Codeine, Phenylephrine

Acetaminophen, Chlorpheniramine, Codeine, Phenylephrine brand name: Colrex.

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

Acetaminophen, Chlorpheniramine, Codeine, Phenylephrine falls into 2 drug categories that Baikal Skullcap can interact with; the most serious is rated moderate. Theoretically, Baikal skullcap may increase levels of drugs metabolized by CYP1A2 enzymes.

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

Baikal Skullcap and Acetaminophen, Chlorpheniramine, Codeine, Phenylephrine

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

Why Are There 2 Interactions?

Baikal Skullcap interacts with whole categories of medication. Acetaminophen, Chlorpheniramine, Codeine, Phenylephrine falls into 2 of those categories, so it can interact with Baikal Skullcap 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 1A2 (CYP1A2) SUBSTRATES

1 of 2

Why this applies to Acetaminophen, Chlorpheniramine, Codeine, Phenylephrine

Acetaminophen, Chlorpheniramine, Codeine, Phenylephrine falls under CYTOCHROME P450 1A2 (CYP1A2) SUBSTRATES — the group Baikal Skullcap interacts with.

Theoretically, Baikal skullcap may increase levels of drugs metabolized by CYP1A2 enzymes.
In vitro evidence suggests that constituents of Baikal skullcap inhibit the activity of CYP1A2. This effect has not been reported in humans.
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

Colrex is a combination product, and this flagged interaction is really about CYP1A2, one of the liver pathways that helps clear certain medicines. In test-tube studies, compounds in Baikal skullcap (like baicalin) appear to slow down CYP1A2. If that happened in people, drugs cleared by this enzyme could build up a bit. For this combo, that mostly affects the acetaminophen portion, where higher levels theoretically add a touch more strain on the liver. You might also feel a little more of the drowsy, dry-mouth effects from the chlorpheniramine and codeine.

Here is the reassuring part: this is lab-only evidence and has never been shown in humans, so the real-world risk looks low. Still, it is worth a quick chat with your pharmacist before combining them.

Contact Dr. Brian directly if you have additional questions on this interaction
References
  1. Kim, B. R., Kim, D. H., Park, R., Kwon, K. B., Ryu, D. G., Kim, Y. C., Kim, N. Y., Jeong, S., Kang, B. K., and Kim, K. S. Effect of an extract of the root of Scutellaria baicalensis and its flavonoids on aflatoxin B1 oxidizing cytochrome P450 enzymes. Pl PubMed
  2. Li, T., Li, N., Guo, Q., Ji, H., Zhao, D., Xie, S., Li, X., Qiu, Z., Han, D., Chen, X., and You, Q. Inhibitory effects of wogonin on catalytic activity of cytochrome P450 enzyme in human liver microsomes. Eur J Drug Metab Pharmacokinet. 6-29-2011; PubMed
Minor

CNS DEPRESSANTS

2 of 2

Acetaminophen, Chlorpheniramine, Codeine, Phenylephrine also falls under CNS DEPRESSANTS.

Theoretically, Baikal skullcap might cause additive therapeutic and adverse effects when used concomitantly with drugs with sedative properties.
In vitro and animal research suggests that Baikal skullcap binds to GABA-A receptors and causes sedation. Theoretically, Baikal skullcap might cause additive therapeutic and adverse effects when used concomitantly with drugs with sedative properties. Preliminary clinical research has not identified clinically relevant sedation after use of Baikal skullcap; however, a thorough evaluation of safety outcomes has not been conducted.
Severity Minor Likelihood Unlikely Evidence D

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

This combination product (Colrex) already has two ingredients that can make you drowsy: the antihistamine chlorpheniramine and the opioid codeine. In lab and animal studies, Baikal skullcap seems to gently nudge the same calming brain receptors (GABA-A), so the worry here is simply adding sleepiness on top of sleepiness. That could mean more grogginess, dizziness, or feeling foggy, especially if you're driving or have a few drinks.

The good news is this is rated minor and unlikely, and it's based only on test-tube and animal work, not solid human data. So I wouldn't lose sleep over it. Still, since codeine and chlorpheniramine already sedate, just keep an eye on how tired you feel and check with your pharmacist or doctor before pairing them.

Contact Dr. Brian directly if you have additional questions on this interaction
References
  1. Hui KM, Wang XH, Xue H. Interaction of flavones from the roots of Scutellaria baicalensis with the benzodiazepine site. Planta Med 2000;66:91-3.
  2. Liao JF, Wang HH, Chen MC, et al. Benzodiazepine binding site-interactive flavones from Scutellaria baicalensis root. Planta Med 1998;64:571-2.
  3. Chang, H. H., Yi, P. L., Cheng, C. H., Lu, C. Y., Hsiao, Y. T., Tsai, Y. F., Li, C. L., and Chang, F. C. Biphasic effects of baicalin, an active constituent of Scutellaria baicalensis Georgi, in the spontaneous sleep-wake regulation. J Ethnopharmacol. 5- 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

Baikal Skullcap Also Interacts With Other Medications

Baikal Skullcap has 593 moderate, 352 minor known drug interactions in our database — the Acetaminophen, Chlorpheniramine, Codeine, Phenylephrine one above is among them. If you take anything else, check it against the full list below.

Moderate 593 Minor 352 No known interaction 1,885 (incl. Acetaminophen, Chlorpheniramine, Codeine, Phenylephrine)
Taking anything else?

Check Another of Your Medications Against Baikal Skullcap

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

Everything else you take

See Every Supplement That Interacts With Acetaminophen, Chlorpheniramine, Codeine, Phenylephrine

This page covers Baikal Skullcap only. If you take other supplements — a multivitamin, a sleep aid, something for joints — the Acetaminophen, Chlorpheniramine, Codeine, Phenylephrine page lists 338 supplements it has a documented interaction with, worst first, each one explained.

The most serious there right now: 1,4-butanediol (major), Activated Charcoal (major), Asarabacca (major), Beer (major) and Ephedra (major).

By severity: 18 major · 275 moderate · 45 minor.

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

“Someone taking Colrex is usually fighting a miserable cold, and cold season is also when people reach for herbal sleep aids and energy boosters, which is exactly where this list bites hardest. Colrex combines acetaminophen, chlorpheniramine, codeine, and phenylephrine, and 18 of its 338 supplement interactions rate major, enough to war…”

Reviewed by 2 · Jul 18, 2026

Open the Acetaminophen, Chlorpheniramine, Codeine, Phenylephrine interaction page

One more smart check

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

We hold 737 real supplement products containing Baikal Skullcap, each one broken down to its full ingredient list — and combination products often carry several ingredients besides Baikal Skullcap. Your product may carry other ingredients that interact with Acetaminophen, Chlorpheniramine, Codeine, Phenylephrine too, on top of Baikal Skullcap — 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 Baikal Skullcap and Acetaminophen, Chlorpheniramine, Codeine, 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 Baikal Skullcap
Top 25%

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

29 days ago today
Medication Acetaminophen, Chlorpheniramine, Codeine, Phenylephrine
Top 10%

#279 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 Baikal Skullcap

What is Baikal Skullcap?

Baikal Skullcap
  • Inflammation
  • Allergies
  • Anxiety and sleep
  • Immune support
  • Respiratory infections

Baikal skullcap is a traditional Chinese herb (Huang Qin) used for inflammation, allergies, and infections, with active compounds like baicalin and baicalein studied mostly in the lab. Human evidence remains limited, so it should not replace proven treatments. Talk to your pharmacist or doctor before using it, and avoid it in pregnancy and breastfeeding.

Read the full Baikal Skullcap monograph & all interactions
Keep checking

Other Drugs & Baikal Skullcap

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

0Major
593Moderate
352Minor
1,884No known interaction
593 Moderate 352 Minor 1,884 No interaction
Moderate

593 interactions

Showing 60 of 593 moderate interactions — see all 593 on the Baikal Skullcap page.

Minor

352 interactions

Showing 60 of 352 minor interactions — see all 352 on the Baikal Skullcap page.

No interaction 1,884 drugs checked — show the list

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

Showing the 60 most looked-up of 1,884 medications checked with no known interaction — see the full Baikal Skullcap list.

See the full Baikal Skullcap interactions page
See every supplement checked against Acetaminophen, Chlorpheniramine, Codeine, 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
Baikal Skullcap monograph › Uses, safety, and every drug interaction in one place Acetaminophen, Chlorpheniramine, Codeine, Phenylephrine supplement interactions › Every supplement checked against Acetaminophen, Chlorpheniramine, Codeine, 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 Baikal Skullcap and Acetaminophen, Chlorpheniramine, Codeine, Phenylephrine Together: Common Questions

Can you take Baikal Skullcap with Acetaminophen, Chlorpheniramine, Codeine, Phenylephrine?
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 Baikal Skullcap and Acetaminophen, Chlorpheniramine, Codeine, Phenylephrine?
Acetaminophen, Chlorpheniramine, Codeine, Phenylephrine belongs to more than one drug category, and Baikal Skullcap 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 Baikal Skullcap and Acetaminophen, Chlorpheniramine, Codeine, Phenylephrine 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.