Drug & supplement interaction

Black Tea + Ephedrine, Phenobarbital, Theophylline

Ephedrine, Phenobarbital, Theophylline brand name: Tedral.

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

Ephedrine, Phenobarbital, Theophylline falls into 4 drug categories that Black Tea can interact with; the most serious is rated major. Theoretically, concomitant use might increase the risk for simulant adverse effects.

Read the full interaction report
SeverityMajor
LikelihoodProbable
Interactions4
EvidenceD
What do Severity, Likelihood & Evidence mean?
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Interaction report

Black Tea and Ephedrine, Phenobarbital, Theophylline

These two interact in 4 distinct ways. Each one is explained separately below.

Why Are There 4 Interactions?

Black Tea interacts with whole categories of medication. Ephedrine, Phenobarbital, Theophylline falls into 4 of those categories, so it can interact with Black Tea in 4 different ways. We’ve listed each one below — your overall risk is driven by the most serious of them (Major).

Major

EPHEDRINE

1 of 4
Theoretically, concomitant use might increase the risk for simulant adverse effects.
Black tea contains caffeine. There is evidence that using ephedrine with caffeine might increase the risk of serious life-threatening or debilitating adverse effects such as hypertension, myocardial infarction, stroke, seizures, and death. Tell patients to avoid taking caffeine with ephedrine and other stimulants.
Severity Major Likelihood Probable Evidence D

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 with this combo product (Tedral): it already packs the stimulant ephedrine plus theophylline, which itself is chemically a cousin of caffeine. The caffeine in your black tea simply piles more stimulant on top of stimulant. That stacking can push your heart rate and blood pressure up, leave you jittery or shaky, mess with sleep, and in heavier doses has been linked to more serious problems like irregular heartbeats, very high blood pressure, or seizures.

This is mostly a caution from real-world reports rather than airtight studies, but it's worth taking seriously. A single cup of tea is gentler than several cups or strong energy drinks. Please check with your pharmacist or doctor before changing anything, and let them know how much caffeine you typically drink.

Contact Dr. Brian directly if you have additional questions on this interaction
References
  1. Haller CA, Benowitz NL. Adverse cardiovascular and central nervous system events associated with dietary supplements containing ephedra alkaloids. N Engl J Med 2000;343:1833-8. PubMed
  2. Shekelle PG, Hardy ML, Morton SC, et al. Efficacy and safety of ephedra and ephedrine for weight loss and athletic performance: a meta-analysis. JAMA 2003;289:1537-45.. PubMed
  3. Kockler DR, McCarthy MW, Lawson CL. Seizure activity and unresponsiveness after hydroxycut ingestion. Pharmacotherapy 2001;21:647-51.. PubMed
Moderate

STIMULANT DRUGS

2 of 4

Why this applies to Ephedrine, Phenobarbital, Theophylline

Ephedrine, Phenobarbital, Theophylline 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 simple version: this combo product already contains two stimulants, ephedrine and theophylline. The caffeine in black tea is a stimulant too, so adding it on top can pile on. The idea here is one of stacking, not your body breaking the medicine down differently. With more total stimulation, you might notice a faster or pounding heartbeat, jitteriness, trouble sleeping, anxiety, or a temporary bump in blood pressure. Theophylline in particular has a narrow safety window, so extra stimulation can be uncomfortable.

This is mostly expert caution rather than hard proof, and an occasional cup is unlikely to cause trouble for most people. Still, if you drink several cups a day or feel wired, check with your pharmacist or doctor before changing anything.

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

THEOPHYLLINE

3 of 4

Ephedrine, Phenobarbital, Theophylline also falls under THEOPHYLLINE.

Theoretically, black tea might increase the levels and adverse effects of theophylline.
Black tea contains caffeine, which can increase theophylline 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 pill (Tedral) contains theophylline, and that's the piece that matters here. The caffeine in black tea acts a lot like theophylline in your body, and they're both cleared through similar liver pathways. So drinking a lot of black tea can nudge your theophylline levels upward instead of letting it clear normally.

Theophylline has a narrow safety window, meaning small changes can tip you from helpful into too much. If levels creep up, you might notice a jittery or racing heart, nausea, trouble sleeping, headache, or feeling shaky. An occasional cup probably won't cause trouble, but steady heavy tea drinking might. This is partly theoretical, so don't change anything on your own. Just mention your tea habits to your pharmacist or doctor.

Contact Dr. Brian directly if you have additional questions on this interaction
References
  1. Sato J, Nakata H, Owada E, et al. Influence of usual intake of dietary caffeine on single-dose kinetics of theophylline in healthy human subjects. Eur J Clin Pharmacol 1993;44:295-8. PubMed
  2. Jonkman JH, Sollie FA, Sauter R, Steinijans VW. The influence of caffeine on the steady-state pharmacokinetics of theophylline. Clin Pharmacol Ther 1991;49:248-55. PubMed
Moderate

PHENOBARBITAL (Luminal)

4 of 4
Theoretically, black tea might reduce the effects of phenobarbital and increase the risk for convulsions.
Black tea contains caffeine. Animal research suggests that caffeine can decrease the anticonvulsant activity of phenobarbital. The exact mechanism of this interaction is unclear.
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

This combination product contains phenobarbital, a barbiturate used in part for its anti-seizure effect. The concern here is the caffeine in black tea. In animal studies, caffeine appeared to blunt phenobarbital's ability to control seizures, which could theoretically raise the chance of convulsions. The reason isn't fully understood, and we don't have solid human evidence, so I wouldn't lose sleep over an occasional cup.

Keep in mind I'm talking about large or concentrated caffeine intake, not the small amount in a single tea. Caffeine can also add to phenobarbital's stimulant-versus-sedative tug-of-war and may affect sleep. If you drink a lot of tea daily or notice any breakthrough symptoms, please check with your pharmacist or doctor before changing anything.

Contact Dr. Brian directly if you have additional questions on this interaction
References
  1. Gasior, M., Borowicz, K., Buszewicz, G., Kleinrok, Z., and Czuczwar, S. J. Anticonvulsant activity of phenobarbital and valproate against maximal electroshock in mice during chronic treatment with caffeine and caffeine discontinuation. Epilepsia 1996;37(3 PubMed
  2. Jankiewicz, K., Chroscinska-Krawczyk, M., Blaszczyk, B., and Czuczwar, S. J. [Caffeine and antiepileptic drugs: experimental and clinical data]. Przegl.Lek. 2007;64(11):965-967.
  3. Chroscinska-Krawczyk, M., Jargiello-Baszak, M., Walek, M., Tylus, B., and Czuczwar, S. J. Caffeine and the anticonvulsant potency of antiepileptic drugs: experimental and clinical data. Pharmacol.Rep. 2011;63(1):12-18. 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 7 major, 572 moderate, 114 minor known drug interactions in our database — the Ephedrine, Phenobarbital, Theophylline one above is among them. If you take anything else, check it against the full list below.

Major 7 Moderate 572 Minor 114 No known interaction 2,137 (incl. Ephedrine, Phenobarbital, Theophylline)
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 Ephedrine, Phenobarbital, Theophylline

This page covers Black Tea only. If you take other supplements — a multivitamin, a sleep aid, something for joints — the Ephedrine, Phenobarbital, Theophylline page lists 184 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), Beer (major), Caffeine (major) and Coffee (major).

By severity: 22 major · 140 moderate · 22 minor.

Open the Ephedrine, Phenobarbital, Theophylline 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 Ephedrine, Phenobarbital, Theophylline 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 Ephedrine, Phenobarbital, Theophylline 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%

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

29 days ago today
Medication Ephedrine, Phenobarbital, Theophylline
Top 5%

#111 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.

7Major
572Moderate
114Minor
2,136No known interaction
7 Major 572 Moderate 114 Minor 2,136 No interaction
Major

7 interactions

Moderate

572 interactions

Showing 60 of 572 moderate interactions — see all 572 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 Ephedrine, Phenobarbital, Theophylline, 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 Ephedrine, Phenobarbital, Theophylline supplement interactions › Every supplement checked against Ephedrine, Phenobarbital, Theophylline, 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 Ephedrine, Phenobarbital, Theophylline Together: Common Questions

Can you take Black Tea with Ephedrine, Phenobarbital, Theophylline?
This is rated a major interaction, so the combination is best avoided unless your doctor or pharmacist has specifically told you otherwise. Read the full details on this page and confirm with your pharmacist before combining them.
Why are there 4 interactions listed for Black Tea and Ephedrine, Phenobarbital, Theophylline?
Ephedrine, Phenobarbital, Theophylline 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 Ephedrine, Phenobarbital, Theophylline interaction?
We rate it Major. This is a clinically significant combination that is generally best avoided, or used only under the direct supervision of your physician or 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.