Drug & supplement interaction

Gamma Butyrolactone (gbl) + Codeine Phosphate, Pseudoephedrine

Codeine Phosphate, Pseudoephedrine brand names: Nucofed, Kg Fed.

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

Codeine Phosphate, Pseudoephedrine 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 Codeine Phosphate, Pseudoephedrine

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. Codeine Phosphate, Pseudoephedrine 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 Codeine Phosphate, Pseudoephedrine

Codeine Phosphate, Pseudoephedrine 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

First, an important safety point: GBL is not a supplement. It is a toxic industrial solvent that your body turns into GHB, a strong sedative, and it is illegal to sell for human use. Please don't take it. If you're struggling with sleep, anxiety, or substance use, reach out to a doctor or pharmacist.

Here's the concern with your product: the codeine part is an opioid that already slows breathing and causes drowsiness. GHB pushes the brain in the same sedating direction. Combining them could stack that slowdown, leading to heavy sedation, very slow or shallow breathing, and even loss of consciousness. This warning is based on anecdotal reports rather than strong studies, but the danger is real enough that I'd urge you not to mix them. Talk with your pharmacist about safer options.

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

NARCOTIC DRUGS

2 of 2

Codeine Phosphate, Pseudoephedrine also falls under NARCOTIC DRUGS.

Theoretically, concomitant use of GBL with narcotic drugs may potentiate respiratory and central nervous system (CNS) depression.
GBL is metabolized to gamma-hydroxybutyrate (GHB). Concomitant use of narcotic drugs with GHB may cause serious CNS and respiratory depression. In one case report, concurrent use of GHB and heroin was fatal.
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

First, a serious safety note: GBL is not a supplement. It is a toxic industrial solvent that your body turns into GHB, a powerful sedative. It is illegal to sell for human use, and it can cause coma, seizures, and death even on its own.

The worry here is that this medicine contains codeine, an opioid that already slows your breathing and your nervous system. Stacking GBL's deep sedation on top of codeine can add up dangerously. You could become very drowsy, breathe too slowly or shallowly, pass out, or stop breathing. This is mostly based on case reports rather than large studies, but one report of GHB combined with another opioid was fatal. Please do not use GBL, and talk with your doctor or pharmacist for safe options.

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. Ferrara SD, Tedeschi L, Frison G, Rossi A. Fatality due to gamma-hydroxybutyric acid (GHB) and heroin intoxication. J Forensic Sci 1995;40:501-4. DOI
  4. 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 Codeine Phosphate, Pseudoephedrine 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. Codeine Phosphate, Pseudoephedrine)
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 Codeine Phosphate, Pseudoephedrine

This page covers Gamma Butyrolactone (gbl) only. If you take other supplements — a multivitamin, a sleep aid, something for joints — the Codeine Phosphate, Pseudoephedrine page lists 176 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), Ephedra (major) and Gamma-hydroxybutyrate (ghb) (major).

By severity: 11 major · 142 moderate · 23 minor.

From our pharmacist’s overview on the Codeine Phosphate, Pseudoephedrine page

“Alcohol is the clearest danger here. Beer and wine both carry a major rating with codeine phosphate and pseudoephedrine (Nucofed, Kg Fed), because alcohol deepens the sedation the codeine half already causes, and that effect is well documented in people.”

Reviewed by 2 · Jul 18, 2026

Open the Codeine Phosphate, Pseudoephedrine interaction page

How much people look this up

Where Gamma Butyrolactone (gbl) and Codeine Phosphate, Pseudoephedrine 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

#1,208 of 1,452 supplements looked up here in the last 7 days

29 days ago today
Medication Codeine Phosphate, Pseudoephedrine
Steady interest

#1,999 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
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 Codeine Phosphate, Pseudoephedrine, 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 Codeine Phosphate, Pseudoephedrine supplement interactions › Every supplement checked against Codeine Phosphate, Pseudoephedrine, 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 Gamma Butyrolactone (gbl) and Codeine Phosphate, Pseudoephedrine Together: Common Questions

Can you take Gamma Butyrolactone (gbl) with Codeine Phosphate, Pseudoephedrine?
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 Codeine Phosphate, Pseudoephedrine?
Codeine Phosphate, Pseudoephedrine 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 Codeine Phosphate, Pseudoephedrine 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 Codeine Phosphate, Pseudoephedrine 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.