Drug & supplement interaction

Bishop's Weed + Chlorpheniramine, Phenylephrine, Phenyltoloxamine

Chlorpheniramine, Phenylephrine, Phenyltoloxamine brand names: Com Time, Q Hist LA, Comhist LA, Linhist LA, Comhist.

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

Chlorpheniramine, Phenylephrine, Phenyltoloxamine falls into 2 drug categories that Bishop's Weed can interact with; the most serious is rated moderate. Bishop's weed constituents seem to cause photosensitivity.

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

Bishop's Weed and Chlorpheniramine, Phenylephrine, Phenyltoloxamine

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

Why Are There 2 Interactions?

Bishop's Weed interacts with whole categories of medication. Chlorpheniramine, Phenylephrine, Phenyltoloxamine falls into 2 of those categories, so it can interact with Bishop's Weed in 2 different ways. We’ve listed each one below — your overall risk is driven by the most serious of them (Moderate).

Moderate

PHOTOSENSITIZING DRUGS

1 of 2

Why this applies to Chlorpheniramine, Phenylephrine, Phenyltoloxamine

Chlorpheniramine, Phenylephrine, Phenyltoloxamine falls under PHOTOSENSITIZING DRUGS — the group Bishop's Weed interacts with.

Bishop's weed constituents seem to cause photosensitivity. Theoretically, concomitant use of bishop's weed with photosensitizing drugs might result in increased photosensitivity.
Some drugs that cause photosensitivity include amitriptyline (Elavil), quinolones (Ciprofloxacin, others), sulfa drugs (Septra, Bactrim, others), and tetracycline.
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 thing to know about combining Bishop's Weed with your Comhist-type product (the chlorpheniramine, phenylephrine, and phenyltoloxamine combo): Bishop's Weed contains psoralens, natural compounds that make your skin more sensitive to sunlight. This isn't about how your body breaks down the medication. It's simply that one of the ingredients here, the antihistamine portion, can also nudge skin toward sun sensitivity. Stack the two together and you may be more likely to get an exaggerated sunburn, redness, or rash with less sun than usual.

I'll be honest with you, this concern rests on weak, anecdotal evidence, so it's more theoretical than proven. Still, if you're using both, play it safe with sunscreen and covered skin, and check in with your pharmacist or doctor before going further.

Contact Dr. Brian directly if you have additional questions on this interaction
References
  1. Ossenkoppele PM, van der Sluis WG, van Vloten WA. [Phototoxic dermatitis following the use of Ammi majus fruit for vitiligo]. Ned Tijdschr Geneeskd 1991;135:478-80.
  2. Dr. Duke's Phytochemical and Ethnobotanical Databases. Available at: http://www.ars-grin.gov/duke/.
Moderate

CYTOCHROME P450 3A4 (CYP3A4) SUBSTRATES

2 of 2

Chlorpheniramine, Phenylephrine, Phenyltoloxamine also falls under CYTOCHROME P450 3A4 (CYP3A4) SUBSTRATES.

Bergapten, a constituent of bishop's weed, has been shown to inhibit cytochrome P450 3A4 (CYP3A4) in vitro. Theoretically, bishop's weed might inhibit elimination and increase blood levels of drugs metabolized by CYP3A4.
Some drugs metabolized by CYP3A4 include alprazolam (Xanax), amitriptyline (Elavil), amiodarone (Cordarone), buspirone (Buspar), cerivastatin (Baycol), citalopram (Celexa), felodipine (Plendil), fexofenadine (Allegra), itraconazole (Sporanox), ketoconazole (Nizoral), lansoprazole (Prevacid), losartan (Cozaar), lovastatin (Mevacor), ondansetron (Zofran), prednisone (Deltasone, Orasone), sertraline (Zoloft), sibutramine (Meridia), sildenafil (Viagra), simvastatin (Zocor), verapamil (Calan, Covera-HS, Isoptin), and many others.
Severity Moderate 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

This combination product blends an antihistamine (chlorpheniramine), a decongestant (phenylephrine), and a second antihistamine (phenyltoloxamine). Bishop's Weed contains a compound called bergapten that can slow down a liver enzyme (CYP3A4) used to clear several medicines. In theory, that could let these cold and allergy ingredients linger longer in your body and hit a little harder.

If that happened, you might feel extra drowsy, dry-mouthed, dizzy, or notice a faster heartbeat or jitteriness from the decongestant part. I'll be honest with you though: this interaction is mostly based on lab studies, not strong human data, so it's a possible concern rather than a proven one. Since Bishop's Weed itself can be toxic, please don't take it on your own. Check with your pharmacist or doctor first.

Contact Dr. Brian directly if you have additional questions on this interaction
References
  1. Malhotra S, Bailey DG, Paine MF, Watkins PB. Seville orange juice-felodipine interaction: comparison with dilute grapefruit juice and involvement of furocoumarins. Clin Pharmacol Ther 2001;69:14-23. 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

Bishop's Weed Also Interacts With Other Medications

Bishop's Weed has 953 moderate known drug interactions in our database — the Chlorpheniramine, Phenylephrine, Phenyltoloxamine one above is among them. If you take anything else, check it against the full list below.

Moderate 953 No known interaction 1,877 (incl. Chlorpheniramine, Phenylephrine, Phenyltoloxamine)
Taking anything else?

Check Another of Your Medications Against Bishop's Weed

Covers the 2,830 medications we’ve checked against Bishop's Weed. Pick one to open its full report.

Everything else you take

See Every Supplement That Interacts With Chlorpheniramine, Phenylephrine, Phenyltoloxamine

This page covers Bishop's Weed only. If you take other supplements — a multivitamin, a sleep aid, something for joints — the Chlorpheniramine, Phenylephrine, Phenyltoloxamine page lists 229 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), Henbane (major) and Lithium (major).

By severity: 10 major · 175 moderate · 44 minor.

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

“If you take Comhist (chlorpheniramine, phenylephrine, and phenyltoloxamine, a cold and allergy combination), treat its supplement list with real care. Ten of the 229 ingredients on file carry a major rating, and the biggest patterns are worth knowing.”

Reviewed by 2 · Jul 18, 2026

Open the Chlorpheniramine, Phenylephrine, Phenyltoloxamine interaction page

One more smart check

Taking Bishop's Weed as Part of a Dietary Supplement Product? Check It for Interactions

We hold 83 real supplement products containing Bishop's Weed, each one broken down to its full ingredient list — and combination products often carry several ingredients besides Bishop's Weed. Your product may carry other ingredients that interact with Chlorpheniramine, Phenylephrine, Phenyltoloxamine too, on top of Bishop's Weed — 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 Bishop's Weed and Chlorpheniramine, Phenylephrine, Phenyltoloxamine 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 Bishop's Weed
Top 25%

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

29 days ago today
Medication Chlorpheniramine, Phenylephrine, Phenyltoloxamine
Steady interest

#2,763 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 Bishop's Weed

What is Bishop's Weed?

Bishop's Weed
  • Vitiligo (loss of skin color)
  • Psoriasis
  • Digestive complaints
  • Asthma and breathing problems
  • Kidney stones
  • Diuretic (increasing urine)

Bishop's Weed (Ammi majus) is a flowering plant whose seeds contain natural light-sensitizing compounds called psoralens, which have been studied mainly for skin conditions like vitiligo and psoriasis when combined with light therapy. The plant is potentially toxic and can cause severe skin and eye reactions when exposed to sunlight, so it is not something to take on your own. If you are interested in psoralen-based treatments, work with a dermatologist rather than self-treating.

Read the full Bishop's Weed monograph & all interactions
Keep checking

Other Drugs & Bishop's Weed

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

0Major
953Moderate
0Minor
1,876No known interaction
953 Moderate 1,876 No interaction
Moderate

953 interactions

Showing 60 of 953 moderate interactions — see all 953 on the Bishop's Weed page.

No interaction 1,876 drugs checked — show the list

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

Showing the 60 most looked-up of 1,876 medications checked with no known interaction — see the full Bishop's Weed list.

See the full Bishop's Weed interactions page
See every supplement checked against Chlorpheniramine, Phenylephrine, Phenyltoloxamine, 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
Bishop's Weed monograph › Uses, safety, and every drug interaction in one place Chlorpheniramine, Phenylephrine, Phenyltoloxamine supplement interactions › Every supplement checked against Chlorpheniramine, Phenylephrine, Phenyltoloxamine, 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 Bishop's Weed and Chlorpheniramine, Phenylephrine, Phenyltoloxamine Together: Common Questions

Can you take Bishop's Weed with Chlorpheniramine, Phenylephrine, Phenyltoloxamine?
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 Bishop's Weed and Chlorpheniramine, Phenylephrine, Phenyltoloxamine?
Chlorpheniramine, Phenylephrine, Phenyltoloxamine belongs to more than one drug category, and Bishop's Weed 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 Bishop's Weed and Chlorpheniramine, Phenylephrine, Phenyltoloxamine 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.