Drug & supplement interaction

Black Tea + Guaifenesin, Phenylpropanolamine

Guaifenesin, Phenylpropanolamine brand names: Entex LA, Miraphen PE, Dura-Vent, Guaifed, Guaifed-PD, and others.

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

Guaifenesin, Phenylpropanolamine falls into 2 drug categories that Black Tea can interact with; the most serious is rated moderate. Theoretically, concomitant use might increase stimulant adverse effects.

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

Black Tea and Guaifenesin, Phenylpropanolamine

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

Why Are There 2 Interactions?

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

Moderate

STIMULANT DRUGS

1 of 2

Why this applies to Guaifenesin, Phenylpropanolamine

Guaifenesin, Phenylpropanolamine falls under STIMULANT DRUGS — the group Black Tea interacts with.

Theoretically, concomitant use might increase stimulant adverse effects.
Black tea contains caffeine. Due to the central nervous system (CNS) stimulant effects of caffeine, concomitant use with stimulant drugs can increase the risk of adverse effects.
Severity Moderate Likelihood Probable Evidence C

Interaction 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..

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

Here's the thing to know about this combo product: the phenylpropanolamine part is a decongestant stimulant that can already raise your heart rate and blood pressure and leave you feeling a bit wired. The guaifenesin component just thins mucus and doesn't really play into this. So the interaction is really between the caffeine in black tea and that stimulant ingredient.

When you stack two stimulants together, the effects can add up. You might notice a faster or pounding heartbeat, jitteriness, trouble sleeping, headache, or a bump in blood pressure. This is more of a theoretical, common-sense caution than something proven by hard studies. A cup or two of tea is usually no big deal, but heavy tea or coffee drinking is where it matters most. If you have high blood pressure or a heart condition, please check with your pharmacist or doctor before pairing them.

Contact Dr. Brian directly if you have additional questions on this interaction
References
  1. Institute of Medicine. Caffeine for the Sustainment of Mental Task Performance: Formulations for Military Operations. Washington, DC: National Academy Press, 2001. Available at: http://books.nap.edu/books/0309082587/html/index.html. DOI
Moderate

PHENYLPROPANOLAMINE

2 of 2

Guaifenesin, Phenylpropanolamine also falls under PHENYLPROPANOLAMINE.

Theoretically, phenylpropanolamine might increase the risk of hypertension, as well as the levels and adverse effects of caffeine.
Black tea contains caffeine. Concomitant use of phenylpropanolamine and caffeine might cause an additive increase in blood pressure. Phenylpropanolamine also seems to increase caffeine serum levels.
Severity Moderate Likelihood Probable Evidence B

Interaction 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..

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

The combo product you're asking about pairs guaifenesin (a plain mucus thinner that doesn't cause this issue) with phenylpropanolamine, a decongestant-type stimulant. Here's the part to watch: phenylpropanolamine can nudge your blood pressure up on its own, and the caffeine in black tea can add to that effect. So drinking strong tea while taking this could mean a bit more of a jittery, racing-heart, headachy, or higher-blood-pressure feeling.

There's also a two-way street here. Phenylpropanolamine appears to slow how your body clears caffeine, so the caffeine may hang around longer and hit harder than usual. The evidence is real but modest, and an occasional cup is different from heavy tea drinking. If you have high blood pressure or heart concerns, check with your pharmacist or doctor first.

Contact Dr. Brian directly if you have additional questions on this interaction
References
  1. Brown NJ, Ryder D, Branch RA. A pharmacodynamic interaction between caffeine and phenylpropanolamine. Clin Pharmacol Ther 1991;50:363-71. PubMed
  2. Lake CR, Rosenberg DB, Gallant S, et al. Phenylpropanolamine increases plasma caffeine levels. Clin Pharmacol Ther 1990;47:675-85. 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

Black Tea Also Interacts With Other Medications

Black Tea has 8 major, 571 moderate, 114 minor known drug interactions in our database — the Guaifenesin, Phenylpropanolamine one above is among them. If you take anything else, check it against the full list below.

Major 8 Moderate 571 Minor 114 No known interaction 2,137 (incl. Guaifenesin, Phenylpropanolamine)
Taking anything else?

Check Another of Your Medications Against Black Tea

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

Everything else you take

See Every Supplement That Interacts With Guaifenesin, Phenylpropanolamine

This page covers Black Tea only. If you take other supplements — a multivitamin, a sleep aid, something for joints — the Guaifenesin, Phenylpropanolamine page lists 62 supplements it has a documented interaction with, worst first, each one explained.

The most serious there right now: Activated Charcoal (major), Ephedra (major), Peyote (major), Rauvolfia Vomitoria (major) and Sida Cordifolia (major).

By severity: 5 major · 44 moderate · 13 minor.

From our pharmacist’s overview on the Guaifenesin, Phenylpropanolamine page

“Ephedra is the entry I'd want anyone taking guaifenesin with phenylpropanolamine (Entex LA, Guaifed, Dura-Vent) to understand first. Phenylpropanolamine is a stimulant decongestant that can raise blood pressure on its own, and ephedra, along with three other stimulant herbs rated major, can stack on that effect and strain the heart.”

Reviewed by 2 · Jul 18, 2026

Open the Guaifenesin, Phenylpropanolamine interaction page

One more smart check

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

We hold 271 real supplement products containing Black Tea, each one broken down to its full ingredient list — and combination products often carry several ingredients besides Black Tea. Your product may carry other ingredients that interact with Guaifenesin, Phenylpropanolamine too, on top of Black Tea — 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 Black Tea and Guaifenesin, Phenylpropanolamine 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 Black Tea
Top 25%

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

29 days ago today
Medication Guaifenesin, Phenylpropanolamine
Steady interest

#1,625 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 Black Tea

What is Black Tea?

  • Mental alertness and energy
  • Heart health support
  • Blood pressure and cholesterol
  • Digestive complaints
  • Weight management
  • Antioxidant support

Black tea is a popular caffeinated drink made from the fully oxidized leaves of the Camellia sinensis plant, and it contains caffeine and antioxidant plant compounds. Moderate tea drinking is generally safe for most adults and may modestly support heart health and alertness, but it is not a proven treatment for any disease. If you are pregnant, breastfeeding, sensitive to caffeine, or taking medicines, talk to your pharmacist or doctor.

Read the full Black Tea monograph & all interactions
Keep checking

Other Drugs & Black Tea

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

8Major
571Moderate
114Minor
2,136No known interaction
8 Major 571 Moderate 114 Minor 2,136 No interaction
Major

8 interactions

Moderate

571 interactions

Showing 60 of 571 moderate interactions — see all 571 on the Black Tea page.

Minor

114 interactions

Showing 60 of 114 minor interactions — see all 114 on the Black Tea page.

No interaction 2,136 drugs checked — show the list

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

Showing the 60 most looked-up of 2,136 medications checked with no known interaction — see the full Black Tea list.

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

Can you take Black Tea with Guaifenesin, Phenylpropanolamine?
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 Black Tea and Guaifenesin, Phenylpropanolamine?
Guaifenesin, Phenylpropanolamine belongs to more than one drug category, and Black Tea 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 Black Tea and Guaifenesin, Phenylpropanolamine 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.