Racetam • Sublingual • GABA-B Modulator

Fasoracetam: The GABA-B Restoring Racetam

Last updated: March 2026

Fasoracetam stands apart from other racetams by upregulating GABA-B receptors rather than primarily enhancing choline uptake. It completed Phase 2 clinical trials in adolescents with ADHD carrying metabotropic glutamate receptor (mGluR) gene variants, and is used to reverse phenibut and baclofen tolerance.

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Sublingual Dose Range
Hold 1-2 Min Under Tongue
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Clinical Trial Stage Reached
NFC-1 ADHD Program
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Adolescents in NFC-1 Trial
mGluR Mutation Cohort

How Fasoracetam Works

Fasoracetam's pharmacology is distinct from most other racetams. While piracetam and oxiracetam focus on AMPA/NMDA glutamate modulation and HACU, fasoracetam's primary characterized effect is upregulation of GABA-B receptors and modulation of metabotropic glutamate receptors (mGluR1 and mGluR5). This makes it uniquely relevant for GABA-dependent conditions.

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GABA-B Receptor Upregulation

Fasoracetam upregulates GABA-B receptors in the brain — increasing both receptor expression and sensitivity. GABA-B receptors are the targets of baclofen and phenibut. Chronic use of those substances causes receptor downregulation (tolerance). Fasoracetam reverses this process, restoring receptor density and re-sensitizing the GABA-B system. This is its most unique and clinically relevant mechanism.

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mGluR Modulation (ADHD Connection)

Fasoracetam modulates metabotropic glutamate receptors (mGluR1 and mGluR5). In the NFC-1 trial, adolescents selected for ADHD specifically needed to carry mutations in mGluR-related genes (CNTN4, CNTNAP2, GRM7 and others). This suggests fasoracetam's ADHD benefit is specifically mediated via mGluR pathways — not necessarily applicable to all ADHD subtypes.

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High-Affinity Choline Uptake

Like other racetams, fasoracetam also enhances high-affinity choline uptake (HACU) in cortical and hippocampal neurons, increasing acetylcholine availability. This is a secondary mechanism compared to its GABA-B effects but contributes to its cognitive profile. As with other racetams, choline supplementation may reduce headache risk and improve effects.

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Sublingual Bioavailability

Fasoracetam is typically administered sublingually at 20-100mg doses. Sublingual absorption bypasses first-pass hepatic metabolism, producing faster onset (~15-30 minutes) compared to oral administration. The compound is held under the tongue for 1-2 minutes. Some users also dissolve powder in water for oral use, though bioavailability may differ between routes.

What the Literature Shows

Fasoracetam has more clinical trial data than most nootropic racetams, thanks to its development as NFC-1 by NeuroFix. The ADHD trials specifically targeted adolescents with mGluR gene mutations — an important patient-selection caveat.

ADHD-RS Score Improvement (NFC-1 Phase 2)
vs placebo in adolescents with mGluR gene variants (n=~30)
Significant
GABA-B Receptor Upregulation (Preclinical)
Receptor binding/expression increase vs vehicle control
Significant
Phenibut Tolerance Restoration (Mechanism-Supported)
Via GABA-B upregulation; supported by mechanism, anecdotal reports
Plausible
Memory Improvement (Cognitive Impairment, Animal)
Preclinical passive avoidance and Morris water maze
Significant
Bioavailability (Sublingual vs Oral)
Sublingual estimated to improve Cmax and reduce time to peak vs oral
Superior

Side Effects & Risks

Sedation / Fatigue (High Doses)
GABA-B agonism at high doses may cause drowsiness
~10%
Brain Fog / Cognitive Blunting
Occasionally reported; may reflect over-activation of inhibitory GABA circuits
~5%
Gastrointestinal Upset
Nausea with oral administration; less common sublingually
~5%
Headache
Less common than with other racetams; still possible due to HACU increase
~5%
Interaction Risk (Phenibut/Baclofen Co-Use)
Additive GABA-B effects if taken simultaneously; space use appropriately
Caution

Key Takeaways

✅ What We Know
  • Upregulates GABA-B receptors — unique mechanism among racetams
  • Completed Phase 2 (NFC-1) trials for ADHD in adolescents with mGluR mutations
  • Mechanism supports phenibut/baclofen tolerance reversal via GABA-B upregulation
  • Also modulates mGluR1 and mGluR5 metabotropic glutamate receptors
  • Sublingual administration preferred: 20-100mg, hold under tongue 1-2 minutes
  • Enhances HACU similar to other racetams — choline supplementation still beneficial
⚠️ What We Don't Know
  • ADHD benefit in people without specific mGluR gene mutations is unproven
  • Optimal phenibut tolerance restoration protocol (dose, duration, timing) is undefined
  • Long-term safety data in humans beyond the trial periods is lacking
  • Whether effects are meaningful in cognitively healthy adults without ADHD

🛒 Recommended Products

Fasoracetam is best taken sublingually. Consider a micro-scale for accurate low-dose measurement.

Related Resources

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⚠️ Important Disclaimer

This page is for educational purposes only. It is not medical advice. Fasoracetam is not FDA-approved for any indication and is sold as a research compound. Do not use alongside GABA-active substances (phenibut, baclofen, benzodiazepines) without understanding additive effects. Always consult a qualified healthcare provider before use.