Interactions on record — worth a quick check against your medications. Check your meds →
Dietary supplement

GABAplex Ingredients & Drug Interactions

by Swanson

GABAplex label
See full label image
Capsule Category: Other Combinations
Most serious interaction: Moderate
Clinical methodology reviewed by · Updated Sep 23, 2026 · Label data from the NIH DSLD
What is this page for?

First and foremost: checking GABAplex against your medications. The heart of this page is the interaction checker and the full interaction report — how this product’s ingredients may interact with prescription and over-the-counter medicines you may be taking.

Around that, we add a pharmacist’s high-level view of the product as a whole — what’s inside, the evidence for its stated use, how transparent the label is, and what safety data exists — so you can see the full picture in one place. It’s educational information from our licensed clinical databases and the clinical staff at HelloPharmacist — not medical advice — and we don’t sell or endorse products. Our editorial policy

The interaction bottom line Most serious interaction: Moderate

GABAplex is a dietary supplement by Swanson with 6 active ingredients. Its ingredients are commonly taken for mental focus and alertness, coping with stress, fatigue and sleep loss.Based on those ingredients, 1,296 medications have a known interaction with it, the most serious rated moderate. The ingredients most likely to interact are Bioperine Nature's Thermonutrient, L-Theanine, Gamma Amino Butyric Acid. Use the checker below to test your specific medication, or read the full HelloPharmacist Interaction Report.

Jump to a section

Check Your Meds Against GABAplex by Swanson

Ask about any prescription or over-the-counter medication and we check it for interactions with GABAplex by Swanson — and tell you which ingredient is responsible.

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HelloPharmacist Scorecard of GABAplex by Swanson

Our pharmacy team’s full take, with four database checks built into the cards below — a summary of what is known, not a grade of the product itself.

From our pharmacy team — supplement deep dive

Generated from HelloPharmacist’s pharmacist-curated databases and editorial rules · Last generated Jul 30, 2026

What’s inside

Full disclosure
Ingredient Transparency · database check
Full

Every active ingredient lists its own amount on the label.

Why this rating?
  • The label discloses an exact amount for 6 of its 6 active ingredients.
  • No proprietary blends here — you can verify the dose of every single component.

GABAplex contains six active ingredients: L-tyrosine and L-glycine (amino acids), taurine (another amino acid derivative), L-theanine (found naturally in green tea), GABA (gamma-aminobutyric acid, a neurotransmitter), and black pepper extract (Bioperine, a standardized piperine source). The capsules also contain inactive ingredients—hypromellose, magnesium stearate, rice flour, rice concentrate, and silica—which are fillers and binders.

Does it work?

Moderate evidence
Evidence for Intended Use · database check
By FDA rules, dietary supplements can’t claim to treat, cure, or prevent disease — so labels speak in careful marketing language. We discern each product’s intended use from its name, label claims, and label statements, then grade the clinical evidence for that use. How these ratings are computed
Moderate

Some clinical evidence supports this product's ingredients for its stated purpose, but it isn't conclusive.

Why this rating?
  • The label markets this product for: stress relief and healthy nervous system function.
  • We looked for evidence on: Anxiety, Generalized anxiety disorder (GAD), Cognitive function, Insomnia, Depression, Fatigue — and 4 related terms.
  • The strongest evidence on file: Tyrosine is rated "Possibly Effective" for Cognitive function (Natural Medicines).
  • Also on file: Theanine is rated "Possibly Effective" for Cognitive function.
  • Also on file: Gamma-aminobutyric Acid (gaba) is rated "Insufficient Reliable Evidence To Rate" for Anxiety, Depression, Insomnia.

The evidence for these ingredients is mixed. L-tyrosine is effective for a rare genetic condition (phenylketonuria, or PKU) and possibly effective for cognitive function and memory, though it appears ineffective for athletic performance.

L-glycine is possibly effective for schizophrenia but evidence is insufficient for ADHD, attention, benign prostate enlargement, and cystic fibrosis. Taurine is possibly effective for hepatitis and heart failure (congestive heart failure) but possibly ineffective for weight loss.

L-theanine is possibly effective for cognitive function but evidence is insufficient for age-related cognitive decline, Alzheimer's disease, anxiety, OCD, and cancer. GABA and black pepper both lack sufficient evidence to establish their effectiveness for the conditions studied.

Overall, the product lacks a clear established benefit as a whole.

The evidence, ingredient by ingredient Tyrosine Glycine Taurine Theanine Gamma-aminobutyric Acid (gaba) Black Pepper

How safe is it?

Well-documented data
Safety Information · database check
Well characterized

Adverse-effect, pregnancy, and general safety data are on file for most of these ingredients.

Why this rating?
  • We hold adverse-effect (side-effect) data for 6 of the 6 matched ingredients.
  • Pregnancy & breastfeeding safety ratings cover 6 of 6.
  • General safety write-ups exist for 6 of 6.
  • Remember: this measures how much safety information exists. Thin data is not the same as being safe.

L-tyrosine is generally well tolerated but can cause fatigue, headache, heartburn, and nausea, especially at higher doses. L-glycine is generally well tolerated at typical doses, though mild sedation, irritability, insomnia, and nausea have been rarely reported.

Taurine is generally well tolerated short-term and is naturally present in breast milk, though long-term safety is less certain; constipation, diarrhea, and indigestion are the most common side effects, and rare hypersensitivity reactions have occurred in people sensitive to sulfites. L-theanine may cause headaches, drowsiness, and increased sleep; it should be avoided during pregnancy and breastfeeding due to insufficient safety data.

GABA appears generally well tolerated but lacks thorough safety evaluation; it should be avoided during pregnancy and breastfeeding. Black pepper is generally safe as a food spice but concentrated piperine supplements warrant caution; it may cause a burning aftertaste, indigestion, and reduced taste perception.

Side effects, ingredient by ingredient Tyrosine Glycine Taurine Theanine Gamma-aminobutyric Acid (gaba) Black Pepper

Meds to double-check

Moderate interaction found
Known Interaction Concern · database check
Moderate identified

The most serious documented interaction for these ingredients is Moderate. Check your medications for a personalized result.

Why this rating?
  • 6 of the 6 matched ingredients can interact with medications — Gamma-aminobutyric Acid (gaba), Black Pepper, Taurine, Tyrosine, Theanine, among others.
  • The most serious interaction on file is rated Moderate.
  • Some involve high-stakes drug classes: anticoagulant / antiplatelet drugs; immunosuppressants / transplant drugs; diabetes medications; lithium; Parkinson's medications.
  • For scale: 1,297 individual medications appear in the full list. A big number alone doesn't make a product dangerous — what matters is whether YOUR medication is on it, so run yours through the interaction checker on this page.

Before taking GABAplex, double-check with your doctor or pharmacist if you use seizure medications like phenytoin (Dilantin)—black pepper can significantly raise its blood levels. Also check if you take blood pressure medications, heart drugs like atorvastatin or propranolol, seizure treatments, HIV medications like nevirapine, tuberculosis drugs like rifampin, immunosuppressants like cyclosporine, sedatives, breathing medications like theophylline, or lithium; several ingredients in this product may affect how they work.

Check your own medication Run your meds through the checker above

The bottom line

Scorecard at a glanceFully disclosed formula with some supporting evidence for its stated purpose. Moderate medication interactions have been identified, and safety information is well characterized.

GABAplex is a multi-ingredient supplement whose ingredients have varying levels of evidence—some are possibly effective for specific uses (tyrosine for PKU and memory, taurine for heart function, glycine for schizophrenia), while others lack sufficient data. The product carries documented interactions with over 1,200 individual medications, particularly seizure drugs, blood pressure medications, and several prescription antivirals and heart drugs.

If you take any regular medications, run them through the checker below before starting, and talk with your doctor or pharmacist about whether this product is appropriate for you.

Educational only — not medical advice; always confirm with your pharmacist. Our editorial policy · How we use AI

Assessment coverage: 6 of 6 active ingredients matched to our full ingredient reviews (monographs). Based on the product label dated Feb 22, 2024.

This Scorecard evaluates available label information, ingredient evidence, and known medication-safety considerations. It does not independently verify product identity, purity, potency, contamination, or manufacturing quality. How these ratings are computed

At a glance

General information

Key facts about GABAplex, straight from the product label.

Brand Swanson
Barcode (UPC) 087614029382
Net contents 60 Veggie Capsule(s)
Market status On market
Date entered into DSLD Feb 22, 2024
DSLD ID 308578
Product type Other Combinations
Supplement form Capsule
Dietary claims / uses Nutrient, All Other, Structure/Function
Intended target group(s) Adult (18 - 50 Years)
From the label
Everything in this section is reproduced from the manufacturer’s own product label — it’s the label speaking, not HelloPharmacist. We show it so you can see exactly what the maker states; we don’t verify or endorse those statements.

Supplement Facts

The label details for GABAplex by Swanson, sourced from the NIH Dietary Supplement Label Database.

Supplement Facts

Daily Value (DV) Target Group(s):
Adults and children 4 or more years of age
Minimum serving Sizes:
1 Veggie Capsule(s)
Maximum serving Sizes:
1 Veggie Capsule(s)
Servings per container
60
UPC/BARCODE
087614029382
IngredientAmount% DV
L-Tyrosine100 mg--
L-Glycine250 mg--
Taurine100 mg--
L-Theanine50 mg--
Gamma Amino Butyric Acid250 mg--
Bioperine Nature's Thermonutrient5 mg--

Other ingredients: Hypromellose, Magnesium Stearate, Rice Flour, Rice Concentrate, Silica

Tap any ingredient to jump to its full detail below.

Label statements
These statements are the manufacturer’s wording, reproduced from the product label — the label is saying it, not HelloPharmacist. We don’t verify or endorse them.
Formulation

Advanced relaxation formula to tackle stress overload Helps maintain physical and emotional wellbeing Support healthy brain and nervous system function

Mental and emotional support

General Statements

Science-backed quality since 1969

Suggested/Recommended/Usage/Directions

Suggested use: As a dietary supplement, take one veggie capsule one to two times per day with water.

Brand IP Statement(s)

BioPerine and Nature's Thermonutrient are registered trademarks of Sabinsa Corp. BioPerine is protected under one or more of the following U.S. patents: #5,536,506; #5,744,161; #5,861,415; #5,972,382 and #6,054,585.

Precautions

Warning: For adults only. Keep out of reach of children.

Consult your physician before using this or any product if you are pregnant or nursing, taking medication or have a medical condition.

Do not use if seal is broken.

Storage

Store in a cool, dry place.

FDA Disclaimer Statement

These statements have not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure or prevent any disease.

Formula

GABAplex with L-tyrosine & L-theanine

FDA Statement of Identity

Dietary Supplement

Is this label outdated? Report a formula or label change and our pharmacy team will review it.

See for yourself

GABAplex by Swanson label

The label scan from the NIH Dietary Supplement Label Database. Tap to enlarge.

GABAplex label

Label images are published by the NIH Dietary Supplement Label Database for the version of this product on file. Always read your actual product label.

View the full label (PDF)
What’s inside

The Ingredients in GABAplex by Swanson

These are the 6 active ingredients this product is made of. Select any to open its full monograph.

Serving size1 Veggie Capsule(s) Dosage formCapsule Servings per container60 Amounts shown are per serving.

Most supplement products combine several ingredients, and a medication can interact with the product through any one of them. Each ingredient below shows whether it has known drug interactions.

L-Tyrosine

Interacts with
21 drugs
100 mg per serving

L-tyrosine is an amino acid your body uses to make brain chemicals like dopamine and norepinephrine. Some studies suggest it may help mental performan...

L-Tyrosine monograph & interactions

L-Glycine

Interacts with
1 drug
250 mg per serving

Glycine is a non-essential amino acid your body makes on its own and that also appears in protein-rich foods. It is most studied for improving sleep q...

L-Glycine monograph & interactions

Taurine

Interacts with
173 drugs
100 mg per serving

Taurine is an amino acid your body makes naturally and that you also get from animal foods. It is widely used in energy drinks and sports supplements,...

Taurine monograph & interactions

L-Theanine

Interacts with
565 drugs
50 mg per serving

Theanine (usually L-theanine) is an amino acid found naturally in tea leaves that many people take to feel calmer and less stressed without strong dro...

L-Theanine monograph & interactions

Gamma Amino Butyric Acid

Interacts with
419 drugs
250 mg per serving

GABA is a calming chemical messenger (neurotransmitter) that your body makes on its own, and it is sold as a supplement for stress, anxiety, and sleep...

Gamma Amino Butyric Acid monograph & interactions

Bioperine Nature's Thermonutrient

Interacts with
1,019 drugs
5 mg per serving Form: Piper nigrum

Black pepper is a common kitchen spice that is generally safe in the amounts used in food. Its extract, piperine, is mostly added to supplements to he...

Bioperine Nature's Thermonutrient monograph & interactions

Other (inactive) ingredients: Hypromellose, Magnesium Stearate, Rice Flour, Rice Concentrate, Silica. These complete the product’s ingredient list but are not active constituents.

Interaction report

GABAplex by Swanson Drug Interactions

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Ask about interactions with your drugs in plain English — “Can I take it with lisinopril?” — and we find you the answer in seconds, ingredient by ingredient.

 Go to the checker
1,296Drugs
1,117 Moderate 179 Minor

Ingredients driving the most interactions

Bioperine Nature's Thermonutrient 1,019
L-Theanine 565
Gamma Amino Butyric Acid 419
Taurine 173
L-Tyrosine 21

Individual Drug Interactions

The ingredients in GABAplex interact with 1,296 drugs. Click any drug to see the details.

6 of the 6 ingredients in GABAplex interact with drugs. Each result below shows which ingredient is responsible. Bioperine Nature's Thermonutrient L-Theanine Gamma Amino Butyric Acid Taurine L-Tyrosine L-Glycine

Each ingredient & the kinds of drugs it affects

For each ingredient in GABAplex with known interactions, here are the types of medications they can affect. Open any type for the detail — or search your exact drug in the checker above.

Bioperine Nature's Thermonutrient17 drug types · 1,019 drugs

Anticoagulant/Antiplatelet Drugs

Theoretically, black pepper might increase the risk of bleeding when taken with antiplatelet or anticoagulant drugs.
In vitro research shows that piperine, a constituent of black pepper, seems to inhibit platelet aggregation. This has not been reported in humans.

Likelihood Possible Evidence D
Antidiabetes Drugs

Theoretically, black pepper might increase the risk of hypoglycemia when taken with antidiabetes drugs.
Animal research shows that piperine, a constituent of black pepper, can reduce blood glucose levels. Monitor blood glucose levels closely. Dose adjustments might be necessary.

Likelihood Possible Evidence D
Atorvastatin (Lipitor)

Theoretically, black pepper might increase blood levels of atorvastatin.
Animal research shows that taking piperine, a constituent of black pepper, 35 mg/kg can increase the maximum serum concentration of atorvastatin three-fold. This has not been reported in humans.

Likelihood Possible Evidence D
Cyclosporine (Neoral, Sandimmune)

Theoretically, black pepper might increase the effects and side effects of cyclosporine.
In vitro research shows that piperine, a constituent of black pepper, increases the bioavailability of cyclosporine. This has not been reported in humans.

Likelihood Possible Evidence D
Cytochrome P450 2D6 (Cyp2D6) Substrates

Theoretically, black pepper might increase levels of drugs metabolized by CYP2D6.
In vitro research suggests that some constituents of black pepper inhibit CYP2D6. This has not been reported in humans.

Likelihood Possible Evidence D
Cytochrome P450 3A4 (Cyp3A4) Substrates

Theoretically, black pepper might increase levels of drugs metabolized by CYP3A4.
In vitro research and pharmacokinetic simulation data suggest that piperine, a constituent of black pepper, as well as the pepper fruit seem to inhibit CYP3A4. This has not been reported in humans.

Likelihood Possible Evidence D
Lithium

Theoretically, black pepper might increase blood levels of lithium due to its diuretic effects. The dose of lithium might need to be reduced.
Black pepper is thought to have diuretic properties.

Likelihood Probable Evidence D
Nevirapine (Viramune)

Black pepper might increase blood levels of nevirapine.
Clinical research shows that piperine, a constituent of black pepper, increases the plasma concentration of nevirapine. However, no adverse effects were observed in this study.

Likelihood Probable Evidence D
P-Glycoprotein Substrates

Theoretically, black pepper might increase levels of P-glycoprotein substrates.
In vitro research shows that piperine, a constituent of black pepper, seems to inhibit P-glycoprotein.

Likelihood Possible Evidence D
Pentobarbital (Nembutal)

Theoretically, black pepper might increase the sedative effects of pentobarbital.
Animal research shows that piperine, a constituent of black pepper, increases pentobarbital-induced sleeping time.

Likelihood Possible Evidence D
Phenytoin (Dilantin)

Black pepper might increase blood levels of phenytoin.
Clinical research shows that piperine, a constituent of black pepper, seems to increase absorption, slow elimination, and increase levels of phenytoin. Taking a single dose of black pepper 1 gram along with phenytoin seems to double the serum concentration of phenytoin. Consuming a soup with black pepper providing piperine 44 mg/200 mL of soup along with phenytoin also seems to increase phenytoin levels when compared with consuming the same soup without black pepper.

Likelihood Possible Evidence B
Propranolol (Inderal)

Black pepper might increase blood levels of propranolol.
Clinical research shows that piperine, a constituent of black pepper, seems to increase absorption and slow elimination of propranolol.

Likelihood Possible Evidence B
Rifampin (Rifadin)

Black pepper might increase blood levels of rifampin.
Clinical research shows that piperine, a constituent of black pepper, seems to increase absorption and serum levels of rifampin.

Likelihood Possible Evidence B
Theophylline

Black pepper might increase blood levels of theophylline.
Clinical research shows that piperine, a constituent of black pepper, seems to increase absorption and slow elimination of theophylline.

Likelihood Possible Evidence D
Amoxicillin (Amoxil, Trimox)

Theoretically, black pepper might increase the effects and side effects of amoxicillin.
Animal research shows that taking piperine, a constituent of black pepper, with amoxicillin increases plasma levels of amoxicillin. This has not been reported in humans.

Likelihood Possible Evidence D
Carbamazepine (Tegretol)

Theoretically, black pepper might increase blood levels of carbamazepine, potentially increasing the effects and side effects of carbamazepine.
One clinical study in patients taking carbamazepine 300 mg or 500 mg twice daily shows that taking a single 20 mg dose of purified piperine, a constituent of black pepper, increases carbamazepine levels. Piperine may increase carbamazepine absorption by increasing blood flow to the GI tract, increasing the surface area of the small intestine, or inhibiting cytochrome P450 3A4 (CYP3A4) in the gut wall. Absorption was significantly increased by 7-10 mcg/mL/hour. The time to eliminate carbamazepine was also increased by 4-8 hours. Although carbamazepine levels were increased, this did not appear to increase side effects. In vitro research also shows that piperine can increase carbamazepine levels by 11% in a time-dependent manner.

Likelihood Possible Evidence B
Cytochrome P450 1A2 (Cyp1A2) Substrates

Theoretically, black pepper might decrease levels and clinical effects of drugs metabolized by CYP1A2.
In vitro research suggests that black pepper induces CYP1A2. This has not been reported in humans.

Likelihood Possible Evidence D
Bioperine Nature's Thermonutrient full monograph & interactions

L-Theanine3 drug types · 565 drugs

Antihypertensive Drugs

Theanine might lower blood pressure, potentiating the effects of antihypertensive drugs.
Animal research shows that theanine can lower blood pressure in spontaneously hypertensive animals. Theoretically, concomitant use of theanine and antihypertensive drugs might potentiate the antihypertensive activity.

Likelihood Possible Evidence D
Cns Depressants

Theoretically, theanine might have additive sedative effects when used in conjunction with CNS depressants. However, it is unclear if this concern is clinically relevant.
Theoretically, theanine may compete with glutamate and/or increase plasma gamma-aminobutyric acid (GABA) levels, which could cause CNS depression. In one clinical study, some subjects taking oral theanine reported drowsiness.

Likelihood Unlikely Evidence D
Serotonergic Drugs

Clinical studies regarding the effects of L-theanine on serotonin levels are conflicting. Some studies suggest it can increase serotonin levels in the brain while others report that it may decrease them. Nevertheless, there have been no reports of l-theanine being a causative agent in serotonergic-related side effects or serotonin syndrome.

Likelihood Unlikely Evidence C
L-Theanine full monograph & interactions

Gamma Amino Butyric Acid2 drug types · 419 drugs

Antihypertensive Drugs

Theoretically, taking GABA with antihypertensive drugs might increase the risk of hypotension.
Some clinical research shows that GABA can decrease blood pressure in patients with hypertension.

Likelihood Possible Evidence B
Cns Depressants

Theoretically, GABA might have additive sedative effects when used in conjunction with CNS depressants. However, it is unclear if this concern is clinically relevant.
Endogenous GABA has well-established relaxant effects and GABA(A) receptors have an established physiological role in sleep. However, the effects of GABA supplements are unclear, as it is unknown whether exogenous GABA crosses the blood-brain barrier. Although there have been limited reports of drowsiness or tiredness with GABA supplements, these effects have not been widely reported in clinical studies. Additionally, intravenous GABA 0.1-1 mg/kg has been shown to induce anxiety in a dose-dependent manner.

Likelihood Unlikely Evidence D
Gamma Amino Butyric Acid full monograph & interactions

Taurine2 drug types · 173 drugs

Antihypertensive Drugs

Theoretically, taurine might increase the risk of hypotension when taken with antihypertensive drugs.
Some clinical evidence suggests that taurine can reduce both systolic and diastolic blood pressure.

Likelihood Probable Evidence D
Lithium

Theoretically, taurine might reduce excretion and increase plasma levels of lithium.
Taurine is thought to have diuretic properties, which might reduce the excretion of lithium.

Likelihood Probable Evidence D
Taurine full monograph & interactions

L-Tyrosine2 drug types · 21 drugs

Levodopa

Theoretically, tyrosine might decrease the effectiveness of levodopa.
Tyrosine and levodopa compete for absorption in the proximal duodenum by the large neutral amino acid (LNAA) transport system. Advise patients to separate doses of tyrosine and levodopa by at least 2 hours.

Likelihood Probable Evidence D
Thyroid Hormone

Theoretically, tyrosine might have additive effects with thyroid hormone medications.
Tyrosine is a precursor to thyroxine and might increase levels of thyroid hormones.

Likelihood Probable Evidence D
L-Tyrosine full monograph & interactions

L-Glycine1 drug type · 1 drug

Clozapine (Clozaril)

Theoretically, glycine might decrease the effectiveness of clozapine.
One small clinical study in patients with schizophrenia shows that adding glycine to clozapine therapy worsens symptoms of schizophrenia when compared with clozapine alone. The mechanism of this interaction is unclear.

Likelihood Probable Evidence B
L-Glycine full monograph & interactions
The maker

Brand information

Manufacturer and brand details for GABAplex, from the product label.

Swanson

See all Swanson products
Name
Swanson Health Products
City
Fargo
State
ND
ZipCode
58104
Phone Number
1-800-437-4148
Web Address
swanson.com
Pharmacist Counseling Corner

GABAplex by Swanson: Common Questions

Does GABAplex by Swanson interact with any medications?
Yes. Based on its ingredients, GABAplex has a known interaction with 1,296 medications. Use the checker to see how it interacts with a specific drug.
How can one product interact with so many drugs?
GABAplex contains 6 active ingredients, and an interaction can come from any of them. We check every ingredient, combine the results into one list per medication, and show which ingredient and mechanism is responsible.
Where does this information come from?
The product label data comes from the NIH Dietary Supplement Label Database (DSLD); the interaction data is built on the Natural Medicines database and reviewed by HelloPharmacist pharmacists.
Is L-theanine safe during pregnancy?
No. The safety data on L-theanine during pregnancy are insufficient, so the facts advise against taking it. Talk with your doctor or pharmacist about whether this product is right for you if you're pregnant or planning to become pregnant.
Can I take this if I'm breastfeeding?
It depends on the ingredient. Taurine occurs naturally in breast milk and is likely safe, but L-theanine and GABA should be avoided due to insufficient safety data. L-tyrosine and L-glycine also have cautions. Your own doctor or pharmacist can review your situation.
What are the most common side effects?
L-tyrosine may cause fatigue, headache, heartburn, and nausea. Taurine commonly causes constipation, diarrhea, and indigestion. L-theanine may cause headaches and drowsiness. GABA may cause drowsiness, nausea, and muscle weakness. Black pepper may cause a burning aftertaste and indigestion.
Does this product help with anxiety?
L-theanine and GABA are sometimes used for anxiety, but the evidence in our data is insufficient to confirm effectiveness. If anxiety is your main reason for considering this product, talk with your doctor about treatments with stronger evidence.
Is black pepper safe in this supplement form?
Black pepper is generally safe as a food spice, but concentrated piperine supplements should be used with caution. The main concern is that it can increase blood levels of several prescription medications, so you need to check your medications first.
Does L-glycine help with ADHD?
Evidence is insufficient. The data we hold don't establish whether L-glycine works for ADHD. If you're considering it for that reason, discuss it with your doctor or pharmacist.

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

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Label information is sourced from the NIH Dietary Supplement Label Database and reflects the product version on file; always read your actual product label. This page is for education only and is not a substitute for professional medical advice. Confirm with your pharmacist or doctor before combining supplements and medications.

GABAplex label
Go deeper

The Full Monographs Behind GABAplex’s Ingredients

Every ingredient we hold a full HelloPharmacist monograph for — uses, evidence, safety, and the complete interaction list.

Herb & supplement monograph

Tyrosine

Interacts with 21 drugs

L-tyrosine is an amino acid your body uses to make brain chemicals like dopamine and norepinephrine. Some studies suggest it may help mental performance during short-term stress, sleep loss,...

Read the full Tyrosine monograph → Herb & supplement monograph

Glycine

Interacts with 1 drug

Glycine is a non-essential amino acid your body makes on its own and that also appears in protein-rich foods. It is most studied for improving sleep quality, where early research is promisin...

Read the full Glycine monograph → Herb & supplement monograph

Taurine

Interacts with 173 drugs

Taurine is an amino acid your body makes naturally and that you also get from animal foods. It is widely used in energy drinks and sports supplements, and short-term use appears generally sa...

Read the full Taurine monograph → Herb & supplement monograph

Theanine

Interacts with 565 drugs

Theanine (usually L-theanine) is an amino acid found naturally in tea leaves that many people take to feel calmer and less stressed without strong drowsiness. Early research suggests it may...

Read the full Theanine monograph → Herb & supplement monograph

Gamma-aminobutyric Acid (gaba)

Interacts with 419 drugs

GABA is a calming chemical messenger (neurotransmitter) that your body makes on its own, and it is sold as a supplement for stress, anxiety, and sleep. The science behind oral GABA supplemen...

Read the full Gamma-aminobutyric Acid (gaba) monograph → Herb & supplement monograph

Black Pepper

Interacts with 1,019 drugs

Black pepper is a common kitchen spice that is generally safe in the amounts used in food. Its extract, piperine, is mostly added to supplements to help the body absorb other ingredients (li...

Read the full Black Pepper monograph →
Sources

Sources & How We Checked

GABAplex's label data comes from the NIH Dietary Supplement Label Database; the ingredient interaction data is from the Natural Medicines database, reviewed by our pharmacists.

Content is written and reviewed by licensed HelloPharmacist pharmacists. See our data sources and editorial standards for how this information is built and checked.

The 77 references behind this product’s interaction data

Every citation that drives the interaction findings for this product’s ingredients, from the evidence-graded Natural Medicines (TRC Healthcare) database. Open an ingredient to browse its citations — links open the study on PubMed or the publisher’s site.

Tyrosine 4 references
  1. Meyer JS, Welch KM, Deshmukh VD, et al. Neurotransmitter precursor amino acids in the treatment of multi-infarct dementia and Alzheimer's disease. J Amer Geriat Soc 1977;25:289-98.
  2. DiPiro JT, Talbert RL, Yee GC, et al; eds. Pharmacotherapy: A pathophysiologic approach. 4th ed. Stamford, CT: Appleton & Lange, 1999.
  3. Wood DR, Reimherr FW, Wender PH. Amino acid precursors for the treatment of attention deficit disorder, residual type. Psychopharmacol Bull 1985;21:146-9.
  4. van Spronsen FJ, van Rijn M, Bekhof J. Phenylketonuria: tyrosine supplementation in phenylalanine-restricted diets. Am J Clin Nutr 2001;73:153-7. PubMed

See these in context on the Tyrosine monograph →

Glycine 5 references
  1. Heresco-Levy U, Javitt DC, Ermilov M, et al. Efficacy of high-dose glycine in the treatment of enduring negative symptoms of schizophrenia. Arch Gen Psychiatry 1999;56:29-36.. PubMed
  2. Potkin SG, Jin Y, Bunney BG, Costa J, Gulasekaram B. Effect of clozapine and adjunctive high-dose glycine in treatment-resistant schizophrenia. Am J Psychiatry 1999;156:145-7.. PubMed
  3. Gusev EI, Skvortsova VI, Dambinova SA, et al. Neuroprotective effects of glycine for therapy of acute ischaemic stroke. Cerebrovasc Dis 2000;10:49-60. PubMed
  4. Inagawa K, Kawai N, Ono K, Sukegawa E, Tsubuku S, Takahashi M. Assessment of acute adverse effects of glycine ingestion at a high dose in human volunteers. Seikatsu Eisei. 2006; 50:27-32.
  5. Woods SW, Walsh BC, Hawkins KA, Miller TJ, Saksa JR, D'Souza DC, Pearlson GD, Javitt DC, McGlashan TH, Krystal JH. Glycine treatment of the risk syndrome for psychosis: report of two pilot studies. Eur Neuropsychopharmacol. 2013 Aug;23(8):931-40. PubMed

See these in context on the Glycine monograph →

Taurine 21 references
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  16. Stohs SJ, Miller M. A case study involving allergic reactions to sulfur-containing compounds including, sulfite, taurine, acesulfame potassium and sulfonamides. Food Chem Toxicol. 2014 Jan;63:240-3. PubMed
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  21. Pallangyo P, Bhalia SV, Komba M, et al. Acute Myocardial Infarction Following the Consumption of Energy Drink in a 28-Year-Old Male: A Case Report. J Investig Med High Impact Case Rep. 2023 Jan-Dec;11:23247096231168811. PubMed

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Theanine 6 references
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  2. Haskell, C. F., Kennedy, D. O., Milne, A. L., Wesnes, K. A., and Scholey, A. B. The effects of L-theanine, caffeine and their combination on cognition and mood. Biol.Psychol. 2008;77(2):113-122. PubMed
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Gamma-aminobutyric Acid (gaba) 12 references
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See these in context on the Gamma-aminobutyric Acid (gaba) monograph →

Black Pepper 29 references
  1. Leung AY, Foster S. Encyclopedia of Common Natural Ingredients Used in Food, Drugs and Cosmetics. 2nd ed. New York, NY: John Wiley & Sons, 1996.
  2. Brinker F. Herb Contraindications and Drug Interactions. 2nd ed. Sandy, OR: Eclectic Medical Publications, 1998.
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See these in context on the Black Pepper monograph →

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

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