Drug & supplement interaction

Oolong 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 Oolong 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

Oolong Tea and Guaifenesin, Phenylpropanolamine

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

Why Are There 2 Interactions?

Oolong Tea interacts with whole categories of medication. Guaifenesin, Phenylpropanolamine falls into 2 of those categories, so it can interact with Oolong 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 Oolong Tea interacts with.

Theoretically, concomitant use might increase stimulant adverse effects.
Oolong tea contains caffeine. Due to the CNS stimulant effects of the caffeine constituent of oolong tea, 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 simple version: your medicine pairs guaifenesin (a mucus thinner) with phenylpropanolamine, a decongestant that acts like a stimulant. Oolong tea brings caffeine to the table, which is also a stimulant. So you have two things nudging your system in the same direction. The guaifenesin part doesn't really interact, but the decongestant plus caffeine can add up.

What might you notice? Things like a faster or pounding heartbeat, jitteriness, trouble sleeping, a little extra anxiety, or a bump in blood pressure. This concern is mostly based on expert reasoning rather than hard studies, and a single cup is unlikely to cause trouble for most people. Still, if you drink a lot of tea or have heart or blood pressure issues, please check with your pharmacist or doctor first.

Contact Dr. Brian directly if you have additional questions on this interaction
References
  1. DiPiro JT, Talbert RL, Yee GC, et al; eds. Pharmacotherapy: A pathophysiologic approach. 4th ed. Stamford, CT: Appleton & Lange, 1999.
  2. 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 in oolong tea.
Oolong 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

This combo product pairs guaifenesin (a mucus thinner) with phenylpropanolamine, a decongestant that narrows blood vessels and can nudge your blood pressure up. The guaifenesin piece doesn't really tangle with oolong tea, so the thing to watch is the phenylpropanolamine plus the caffeine in your tea.

Here's the issue: both phenylpropanolamine and caffeine are mild stimulants, so together they can add up and push your blood pressure higher. On top of that, phenylpropanolamine seems to slow how fast your body clears caffeine, so the caffeine can build up and leave you feeling jittery, with a racing heart, headache, or trouble sleeping. The evidence here is modest, but if you have any heart or blood pressure concerns, check with your pharmacist before drinking a lot of oolong tea with this medicine.

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

Oolong Tea Also Interacts With Other Medications

Oolong Tea has 8 major, 517 moderate, 126 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 517 Minor 126 No known interaction 2,179 (incl. Guaifenesin, Phenylpropanolamine)
Taking anything else?

Check Another of Your Medications Against Oolong Tea

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

Everything else you take

See Every Supplement That Interacts With Guaifenesin, Phenylpropanolamine

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

We hold 75 real supplement products containing Oolong Tea, each one broken down to its full ingredient list — and combination products often carry several ingredients besides Oolong Tea. Your product may carry other ingredients that interact with Guaifenesin, Phenylpropanolamine too, on top of Oolong 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 Oolong 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 Oolong Tea
Steady interest

#1,139 of 1,452 supplements looked up here in the last 7 days

29 days ago today
Medication Guaifenesin, Phenylpropanolamine
Steady interest

#1,624 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 Oolong Tea

What is Oolong Tea?

  • Weight management
  • Mental alertness and energy
  • Heart health
  • Blood sugar support
  • Antioxidant support

Oolong tea is a traditional partially oxidized tea made from the same plant as green and black tea, and it provides caffeine and plant antioxidants. As a beverage it is generally considered safe for most healthy adults in moderate amounts, but evidence for specific health benefits like weight loss or blood sugar control is limited. If you have heart, blood pressure, or caffeine-sensitivity concerns, talk with your pharmacist or doctor.

Read the full Oolong Tea monograph & all interactions
Keep checking

Other Drugs & Oolong Tea

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

8Major
517Moderate
126Minor
2,178No known interaction
8 Major 517 Moderate 126 Minor 2,178 No interaction
Major

8 interactions

Moderate

517 interactions

Showing 60 of 517 moderate interactions — see all 517 on the Oolong Tea page.

Minor

126 interactions

Showing 60 of 126 minor interactions — see all 126 on the Oolong Tea page.

No interaction 2,178 drugs checked — show the list

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

Showing the 60 most looked-up of 2,178 medications checked with no known interaction — see the full Oolong Tea list.

See the full Oolong 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
Oolong 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 Oolong Tea and Guaifenesin, Phenylpropanolamine Together: Common Questions

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