Quick Comparison
| Coluracetam | Fasoracetam | |
|---|---|---|
| Half-Life | 2-3 hours | 1.5-2.5 hours |
| Typical Dosage | Standard: 20-80 mg sublingually, 2-3 times daily. Start at 20 mg to assess sensitivity. Sublingual is strongly preferred for bioavailability. | Standard: 20-100 mg sublingually or orally, 1-3 times daily. Many users find 20-40 mg effective. Clinical trials for ADHD used 100-400 mg twice daily. |
| Administration | Sublingual (strongly preferred) or oral. Oral bioavailability is limited. | Oral or sublingual. Sublingual may provide better absorption. |
| Research Papers | 1 papers | 5 papers |
| Categories |
Mechanism of Action
Coluracetam
Coluracetam's primary mechanism is enhancement of high-affinity choline uptake (HACU) in hippocampal neurons — the rate-limiting step in acetylcholine synthesis. HACU is mediated by the high-affinity choline transporter (CHT1/SLC5A7), which coluracetam upregulates or potentiates, increasing the Vmax of choline transport into presynaptic terminals. By making this process more efficient, coluracetam increases acetylcholine production and vesicular packaging via the vesicular acetylcholine transporter (VAChT) even when choline levels are normal. This enhances cholinergic transmission in the hippocampus, cortex, and retina — explaining reports of enhanced color vision and visual acuity. Coluracetam also has minor AMPA receptor positive allosteric modulation. The compound was studied for treatment-resistant depression, possibly through cholinergic modulation of mood circuits.
Fasoracetam
Fasoracetam upregulates GABA-B receptor (GABA-B1/GABA-B2 heterodimer) expression and function, which is unique among racetams — this receptor upregulation is potentially beneficial for restoring GABAergic sensitivity after prolonged benzodiazepine or phenibut use. It enhances group II metabotropic glutamate receptor (mGluR2/mGluR3) signaling, which modulates presynaptic glutamate release and reduces excitotoxicity. Fasoracetam increases acetylcholine release in the cerebral cortex via modulation of choline acetyltransferase activity and vesicular acetylcholine transporter function. It may also modulate the glutamatergic system through mGluR5. The combination of GABAergic (GABA-B-mediated inhibition), glutamatergic (mGluR modulation), and cholinergic enhancement provides anxiolytic effects alongside cognitive enhancement. Clinical trials focus on ADHD patients with GRM (glutamate receptor) gene variants.
Risks & Safety
Coluracetam
Common
Headache, fatigue, brain fog at high doses.
Serious
Very limited human safety data — studied only in small trials.
Rare
Anxiety, irritability, suicidal ideation was reported in one clinical trial participant.
Fasoracetam
Common
Headache, fatigue, mild digestive discomfort.
Serious
Limited long-term human safety data.
Rare
Low mood, brain fog, loss of motivation at very high doses.
Full Profiles
Coluracetam →
A racetam that enhances high-affinity choline uptake (HACU) — the rate-limiting step in acetylcholine synthesis. This makes it uniquely effective at boosting acetylcholine levels, which is why users commonly report enhanced color vision, sharper visual perception, and improved memory. It was briefly studied for treatment-resistant depression.
Fasoracetam →
A newer racetam that uniquely upregulates GABA-B receptors, making it potentially useful for people who have developed tolerance to GABAergic substances like Phenibut or benzodiazepines. It also enhances glutamate and acetylcholine signaling. Being studied in clinical trials for ADHD in adolescents with specific glutamate receptor gene mutations.