Drug & supplement interaction

Gamma Butyrolactone (gbl) + Zonisamide

Zonisamide brand names: Zonegran, Zonisade.

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

Zonisamide falls into 2 drug categories that Gamma Butyrolactone (gbl) can interact with; the most serious is rated moderate. Theoretically, concomitant use of GBL with CNS depressants may potentiate respiratory and CNS depression.

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

Gamma Butyrolactone (gbl) and Zonisamide

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

Why Are There 2 Interactions?

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

Moderate

CNS DEPRESSANTS

1 of 2

Why this applies to Zonisamide

Zonisamide falls under CNS DEPRESSANTS — the group Gamma Butyrolactone (gbl) interacts with.

Theoretically, concomitant use of GBL with CNS depressants may potentiate respiratory and CNS depression.
GBL is metabolized to gamma-hydroxybutyrate (GHB). Concomitant use of CNS depressants with GHB may cause serious CNS and respiratory depression.
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

Let me be straight with you first: GBL is not a supplement. It's a toxic industrial solvent that your body turns into GHB, a heavy-duty sedative. It's illegal for human use and on its own can cause coma, seizures, and death. Please don't take it. If you're struggling with sleep, anxiety, or substance use, reach out to a doctor or pharmacist who can help you safely.

Now, about combining it with zonisamide. Zonisamide already calms electrical activity in the brain, and it can leave you feeling drowsy, foggy, or unsteady. Stacking a powerful sedative like GHB on top of that may deepen that slowdown and, in a worst case, dangerously suppress your breathing. The evidence here is mostly anecdotal, but the risk is real enough that I'd urge you to avoid this pairing entirely and talk with your provider.

Contact Dr. Brian directly if you have additional questions on this interaction
References
  1. Anon. Important message for health professionals: Report serious adverse events associated with dietary supplements containing GBL, GHB or BD. Food and Drug Administration, Rockville, MD. August 25, 1999. Available at: http://vm.cfsan.fda.gov/~dms/mwg
  2. Anon. Multistate outbreak of poisonings associated with illicit use of gamma hydroxy butyrate. JAMA 1991;265:447-8. DOI
  3. Product information for Xyrem. Jazz Pharmaceuticals, Inc. Palo Alto, CA. March 2022.
Moderate

ANTICONVULSANTS

2 of 2

Zonisamide also falls under ANTICONVULSANTS.

Theoretically, concomitant use of GBL with certain anticonvulsants may potentiate respiratory and central nervous system (CNS) depression or increase the risk of seizures.
GBL is metabolized to gamma-hydroxybutyrate (GHB). Concomitant use of anticonvulsants that have sedative effects with GHB may cause serious CNS and respiratory depression. GHB can also cause seizures and might reduce the effectiveness of anticonvulsants.
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

Let me be straight with you: GBL isn't a supplement at all. It's a toxic solvent that your body turns into GHB, a heavy-duty sedative that can cause coma, seizures, and death. So the real concern here isn't a subtle drug interaction, it's that GBL is dangerous on its own.

That said, pairing it with zonisamide raises two specific worries. First, zonisamide can already make you drowsy or slow your breathing, and GHB piles on top of that, which could lead to dangerous sedation or trouble breathing. Second, GHB can actually trigger seizures and may work against the very protection zonisamide is meant to give you. This is based on weak, anecdotal evidence, but the bottom line is simple: please don't use GBL. If you're struggling with sleep, anxiety, or substance use, talk with your doctor or pharmacist.

Contact Dr. Brian directly if you have additional questions on this interaction
References
  1. Anon. Multistate outbreak of poisonings associated with illicit use of gamma hydroxy butyrate. JAMA 1991;265:447-8. DOI
  2. Carotenuto A, De Feo V, Fattorusso E, et al. The flavonoids of Allium ursinum. Phytochem 1996;41:531-6. PubMed
  3. Product information for Xyrem. Jazz Pharmaceuticals, Inc. Palo Alto, CA. March 2022.

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

Gamma Butyrolactone (gbl) Also Interacts With Other Medications

Gamma Butyrolactone (gbl) has 270 moderate known drug interactions in our database — the Zonisamide one above is among them. If you take anything else, check it against the full list below.

Moderate 270 No known interaction 2,560 (incl. Zonisamide)
Taking anything else?

Check Another of Your Medications Against Gamma Butyrolactone (gbl)

Covers the 2,830 medications we’ve checked against Gamma Butyrolactone (gbl). Pick one to open its full report.

Everything else you take

See Every Supplement That Interacts With Zonisamide

This page covers Gamma Butyrolactone (gbl) only. If you take other supplements — a multivitamin, a sleep aid, something for joints — the Zonisamide page lists 206 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 Grapefruit (major).

By severity: 9 major · 157 moderate · 40 minor.

From our pharmacist’s overview on the Zonisamide page

“Zonisamide (Zonegran, Zonisade) keeps seizures under control, which means anything that shifts its blood level or stacks extra sedation on top deserves real respect, and nine of the 206 supplement ingredients on file rate major. Two big themes run through nearly everything here.”

Reviewed by 2 · Jul 18, 2026

Open the Zonisamide interaction page

How much people look this up

Where Gamma Butyrolactone (gbl) and Zonisamide 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 Gamma Butyrolactone (gbl)
Steady interest

#1,219 of 1,452 supplements looked up here in the last 7 days

29 days ago today
Medication Zonisamide
Top 25%

#596 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 Gamma Butyrolactone (gbl)

What is Gamma Butyrolactone (gbl)?

Gamma Butyrolactone (gbl)
  • Recreational intoxication and euphoria
  • Relaxation and sedation
  • Sleep aid (misused)
  • Bodybuilding/muscle building claims (unproven)
  • Industrial solvent and cleaner

Gamma butyrolactone (GBL) is a toxic industrial solvent, not a dietary supplement, and the body converts it into GHB, a powerful and dangerous sedative. It is illegal to sell or possess for human use in the United States, has no proven medical or supplemental benefit, and can cause coma, seizures, and death. Do not take GBL — if you are seeking help for sleep, anxiety, or substance use, talk to a doctor or pharmacist.

Read the full Gamma Butyrolactone (gbl) monograph & all interactions
Medication

About Zonisamide

What Is Zonisamide Used For?

Brand names: Zonegran, Zonisade

Zonisamide is used as add-on therapy — meaning it is combined with other seizure medications, not used alone — to treat partial seizures (seizures that start in one part of the brain) in adults with epilepsy. Zonegran (capsule) and generic zonisamide capsules are approved for adults with epilepsy.

Zonisade (oral suspension) is approved as add-on therapy for partial-onset seizures in adults and in patients 16 years of age and older.

See full Zonisamide drug information
Keep checking

Other Drugs & Gamma Butyrolactone (gbl)

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

0Major
270Moderate
0Minor
2,559No known interaction
270 Moderate 2,559 No interaction
Moderate

270 interactions

Showing 60 of 270 moderate interactions — see all 270 on the Gamma Butyrolactone (gbl) page.

No interaction 2,559 drugs checked — show the list

We also checked Gamma Butyrolactone (gbl) against these medications and found no known interaction in our sources. Open any page to confirm.

Showing the 60 most looked-up of 2,559 medications checked with no known interaction — see the full Gamma Butyrolactone (gbl) list.

See the full Gamma Butyrolactone (gbl) interactions page
See every supplement checked against Zonisamide, 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
Gamma Butyrolactone (gbl) monograph › Uses, safety, and every drug interaction in one place Zonisamide supplement interactions › Every supplement checked against Zonisamide, ranked by severity Zonisamide 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 Gamma Butyrolactone (gbl) and Zonisamide Together: Common Questions

Can you take Gamma Butyrolactone (gbl) with Zonisamide?
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 Gamma Butyrolactone (gbl) and Zonisamide?
Zonisamide belongs to more than one drug category, and Gamma Butyrolactone (gbl) 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 Gamma Butyrolactone (gbl) and Zonisamide 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 Zonisamide and Gamma Butyrolactone (gbl)?

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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.