Drug & supplement interaction

Calabar Bean + Phenobarbital

Phenobarbital brand names: Phenobarbital, Solfoton, Luminal.

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

Calabar Bean has a minor interaction with Phenobarbital. Theoretically, taking calabar bean might reduce the effects of anticholinergic drugs.

Read the full interaction report
SeverityMinor
LikelihoodUnlikely
EvidenceD
What do Severity, Likelihood & Evidence mean?
Know someone taking this? Share
Facebook Post Reddit Email
On this page
Interaction report

Calabar Bean and Phenobarbital

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

Minor

ANTICHOLINERGIC DRUGS

Why this applies to Phenobarbital

Phenobarbital falls under ANTICHOLINERGIC DRUGS — the group Calabar Bean interacts with.

Theoretically, taking calabar bean might reduce the effects of anticholinergic drugs.
Physostigmine, a constituent of calabar bean, reverses the effects of belladonna and other drugs with anticholinergic activity.
Severity Minor Likelihood Unlikely Evidence D

Interaction has been demonstrated in animal or in lab research but has been shown not to occur in humans..

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

First, the big picture: Calabar bean is genuinely poisonous and is not something you should ever eat or take as a supplement. The only safe version is the prescription drug physostigmine, given under a doctor's care. So this is really a pharmacology note, not a green light to combine the two.

On paper, the interaction listed here groups phenobarbital with anticholinergic drugs, where Calabar bean's physostigmine could push in the opposite direction. But phenobarbital isn't really an anticholinergic. It's a barbiturate that calms the brain, helping control seizures and easing anxiety. The bigger concern is that both substances are powerful nervous system actors, and the real risk is poisoning from the bean itself. This is theoretical and weakly supported, so don't panic, but please run any combination past your pharmacist or doctor first.

Contact Dr. Brian directly if you have additional questions on this interaction
References
  1. McEvoy GK, ed. AHFS Drug Information. Bethesda, MD: American Society of Health-System Pharmacists, 1998.

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

Calabar Bean Also Interacts With Other Medications

Calabar Bean has 194 minor known drug interactions in our database — the Phenobarbital one above is one of them. If you take anything else, check it against the full list below.

Minor 194 No known interaction 2,636 (incl. Phenobarbital)
Taking anything else?

Check Another of Your Medications Against Calabar Bean

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

From our Q&A

Questions About Calabar Bean or Phenobarbital

These are real questions from readers, answered by the pharmacists at HelloPharmacist — written by a person, not generated from a database. Each one covers Calabar Bean or Phenobarbital, 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 Phenobarbital

This page covers Calabar Bean only. If you take other supplements — a multivitamin, a sleep aid, something for joints — the Phenobarbital page lists 174 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), Gamma-hydroxybutyrate (ghb) (major) and Henbane (major).

By severity: 10 major · 143 moderate · 21 minor.

Open the Phenobarbital interaction page

How much people look this up

Where Calabar Bean and Phenobarbital 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 Calabar Bean
Steady interest

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

29 days ago today
Medication Phenobarbital
Top half

#1,135 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 Calabar Bean

What is Calabar Bean?

Calabar Bean
  • Source of physostigmine (a prescription drug ingredient)
  • Historically used in 'trial by ordeal' rituals
  • Traditional pain relief and anti-inflammatory uses
  • Historically used for eye conditions (glaucoma)
  • Historically used as a poison

Calabar bean is a highly poisonous West African seed that contains physostigmine, a powerful cholinesterase inhibitor. It is not a safe dietary supplement, and eating the bean can cause serious poisoning or death. Only the purified, regulated drug physostigmine has a legitimate medical use, and that must be prescribed and monitored by a doctor.

Read the full Calabar Bean monograph & all interactions
Medication

About Phenobarbital

What Is Phenobarbital Used For?

Brand names: Phenobarbital, Solfoton, Luminal

Phenobarbital tablets and oral solutions are used to treat generalized and partial seizures and as a sedative. Phenobarbital Sodium injection is used as a long-term anticonvulsant for generalized tonic-clonic and focal seizures, for emergency control of acute convulsive episodes (including status epilepticus), for sedation, short-term treatment of insomnia, and as a preanesthetic. It is also used in pediatric patients as an anticonvulsant and sedative, including before and after surgery.

Sezaby (phenobarbital injection, intravenous) is specifically indicated for the treatment of neonatal seizures in term and preterm infants. It is not approved for use in adolescents or adults.

See full Phenobarbital drug information
Keep checking

Other Drugs & Calabar Bean

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

0Major
0Moderate
194Minor
2,635No known interaction
194 Minor 2,635 No interaction
Minor

194 interactions

Showing 60 of 194 minor interactions — see all 194 on the Calabar Bean page.

No interaction 2,635 drugs checked — show the list

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

Showing the 60 most looked-up of 2,635 medications checked with no known interaction — see the full Calabar Bean list.

See the full Calabar Bean interactions page
See every supplement checked against Phenobarbital, 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
Calabar Bean monograph › Uses, safety, and every drug interaction in one place Phenobarbital supplement interactions › Every supplement checked against Phenobarbital, ranked by severity Phenobarbital drug information › The full plain-English guide to this medication 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 Calabar Bean and Phenobarbital Together: Common Questions

Can you take Calabar Bean with Phenobarbital?
There is only a minor interaction, which is usually not serious. Read the full details on this page and confirm with your pharmacist before combining them.
How serious is the Calabar Bean and Phenobarbital interaction?
We rate it Minor. This interaction is generally not clinically significant, but it remains worth noting and discussing with your pharmacist.

Written and reviewed by the HelloPharmacist editorial staff. Our editorial policy

Still Have a Question About Phenobarbital and Calabar Bean?

Our pharmacists answer your medication & supplement questions — free.

Ask a pharmacist

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.