Drug & supplement interaction

Senna + Phenolphthalein

Phenolphthalein brand names: Modane, Evac-Q-Tab, Modane Mild.

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

Senna has a moderate interaction with Phenolphthalein. Theoretically, senna might increase the risk for fluid and electrolyte loss when taken with other stimulant laxatives.

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

Senna and Phenolphthalein

Here is the interaction we found between these two, with the evidence behind it.

Moderate

STIMULANT LAXATIVES

Why this applies to Phenolphthalein

Phenolphthalein falls under STIMULANT LAXATIVES — the group Senna interacts with.

Theoretically, senna might increase the risk for fluid and electrolyte loss when taken with other stimulant laxatives.
Senna is a stimulant laxative; concomitant use with other stimulant laxatives might compound fluid and electrolyte loss.
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 simple version: both senna and phenolphthalein (you may know it as older products like Modane) are stimulant laxatives. They work in similar ways, nudging your colon to contract and pulling more water into the stool. The concern isn't that one makes the other stronger in your bloodstream. It's that using two laxatives that do the same job can stack their effects.

When you double up, you raise the odds of loose, watery stools, belly cramping, and losing too much fluid along with salts like potassium and sodium. That can leave you feeling weak, dizzy, or dehydrated. This caution is theoretical, based on how these products work rather than hard studies, but it's a sensible one. Please check with your pharmacist or doctor before pairing them.

Contact Dr. Brian directly if you have additional questions on this interaction
References
  1. Brinker F. Herb Contraindications and Drug Interactions. 2nd ed. Sandy, OR: Eclectic Medical Publications, 1998.
  2. Xing JH, Soffer EE. Adverse effects of laxatives. Dis Colon Rectum 2001;44:1201-9. 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

Senna Also Interacts With Other Medications

Senna has 139 moderate known drug interactions in our database — the Phenolphthalein one above is one of them. If you take anything else, check it against the full list below.

Moderate 139 No known interaction 2,691 (incl. Phenolphthalein)
Taking anything else?

Check Another of Your Medications Against Senna

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

From our Q&A

Questions About Senna or Phenolphthalein

These are real questions from readers, answered by the pharmacists at HelloPharmacist — written by a person, not generated from a database. Each one covers Senna or Phenolphthalein, not necessarily both, but if one is close to what you were about to ask it will usually go further than a database entry can:

Not quite your question? Ask our pharmacists directly — it is free, there is no account required, and answers usually come back within 24 hours.

Everything else you take

See Every Supplement That Interacts With Phenolphthalein

This page covers Senna only. If you take other supplements — a multivitamin, a sleep aid, something for joints — the Phenolphthalein page lists 46 supplements it has a documented interaction with, worst first, each one explained.

The most serious there right now: Activated Charcoal (major), Jalap (major), Oleander (major), Alder Buckthorn (moderate) and Aloe (moderate).

By severity: 3 major · 34 moderate · 9 minor.

From our pharmacist’s overview on the Phenolphthalein page

“Phenolphthalein is a stimulant laxative itself, and that is the heart of the problem with these combinations. Most of the herbs on file, jalap being one, act the same way, so pairing them can drain fluid and potassium quickly.”

Reviewed by 2 · Jul 18, 2026

Open the Phenolphthalein interaction page

One more smart check

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

We hold 120 real supplement products containing Senna, each one broken down to its full ingredient list — and combination products often carry several ingredients besides Senna. Your product may carry other ingredients that interact with Phenolphthalein too, on top of Senna — 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 Senna and Phenolphthalein 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 Senna
Top 25%

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

29 days ago today
Medication Phenolphthalein
Top half

#1,093 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 Senna

What is Senna?

Senna
  • Short-term constipation relief
  • Bowel cleansing before procedures
  • Occasional irregularity
  • Traditional digestive remedy

Senna is a plant-based stimulant laxative that is widely used and generally effective for short-term relief of constipation. It is best used occasionally and for only a few days at a time, since long-term use can lead to dependence and other problems. Talk with a pharmacist or doctor before using it regularly or if you have ongoing constipation.

Read the full Senna monograph & all interactions
Keep checking

Other Drugs & Senna

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

0Major
139Moderate
0Minor
2,690No known interaction
139 Moderate 2,690 No interaction
Moderate

139 interactions

Showing 60 of 139 moderate interactions — see all 139 on the Senna page.

No interaction 2,690 drugs checked — show the list

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

Showing the 60 most looked-up of 2,690 medications checked with no known interaction — see the full Senna list.

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

Can you take Senna with Phenolphthalein?
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.
How serious is the Senna and Phenolphthalein 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

Still Have a Question About Phenolphthalein and Senna?

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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.