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Etifoxine
Stresam | Non-benzodiazepine anxiolytic | Dual GABA-A modulator + TSPO ligand → neurosteroid synthesis
Aliases (7)
Overview
What is Etifoxine?
Etifoxine (Stresam) is a non-benzodiazepine anxiolytic of the benzoxazine class, marketed in France since 1979 (Hoechst, then sanofi-aventis, now Biocodex) for adjustment disorder with anxiety. It is unique among clinical anxiolytics in having two distinct converging mechanisms: (1) direct positive allosteric modulation of GABA-A receptors at a non-benzodiazepine site preferring β2/β3 subunit-containing receptors, and (2) high-affinity binding to the translocator protein 18 kDa (TSPO, formerly peripheral benzodiazepine receptor / PBR), driving cholesterol transport into mitochondria and stimulating de novo neurosteroid synthesis (notably allopregnanolone, pregnanolone, and tetrahydrodeoxycorticosterone — themselves potent GABA-A PAMs). It is NOT FDA-approved in the US, NOT DEA-scheduled, and NOT on the WADA Prohibited List. The dual mechanism produces clinically meaningful anxiolysis (head-to-head comparable to lorazepam in the Nguyen 2006 RCT) without the cognitive-impairment, motor-coordination, or dependence/withdrawal liabilities characteristic of benzodiazepines. The principal safety concern is rare-but-real idiosyncratic hepatotoxicity (Cottin et al. 2016 French pharmacovigilance cohort) and rare cutaneous reactions including DRESS and Stevens-Johnson syndrome.
Key Benefits
Anxiolytic efficacy comparable to low-dose benzodiazepines without sedation, cognitive impairment, motor incoordination, anterograde amnesia, or dependence/withdrawal liability. Dual mechanism (direct GABA-A PAM + TSPO-driven neurosteroidogenesis) is unique among approved clinical anxiolytics. Preclinical and small-RCT signals for accelerated peripheral nerve regeneration via TSPO-driven neurosteroid synthesis. Reasonable Tmax (~2-3 hr) and dosing schedule (TID).
Mechanism of Action
Two mechanisms converge on GABA-A inhibitory tone. (1) DIRECT GABA-A modulation: etifoxine binds an allosteric site on GABA-A receptors distinct from the benzodiazepine site, with preference for β2/β3 subunit-containing receptors — increases chloride channel opening when GABA is bound. Subunit profile differs from benzos (which bind α/γ interface). (2) INDIRECT via TSPO: etifoxine is a high-affinity ligand at the translocator protein 18 kDa (TSPO, formerly PBR) on the outer mitochondrial membrane. TSPO activation drives cholesterol import into mitochondria, where StAR-coupled steroidogenesis converts cholesterol → pregnenolone → allopregnanolone (3α,5α-tetrahydroprogesterone), pregnanolone, and tetrahydrodeoxycorticosterone (THDOC). These neurosteroids are potent positive allosteric modulators of GABA-A receptors at a separate neurosteroid binding site. The net effect is GABA-A enhancement via three converging routes (direct PAM + two endogenous neurosteroid PAMs) without the abuse-liability + dependence-loop pharmacology of pure-benzodiazepine α1 activation. Metabolized hepatically (CYP-mediated) to diethyl-etifoxine — an active metabolite with longer half-life (~20 hr) that contributes substantially to therapeutic effect.
Pharmacokinetics
Research Indications
The dual mechanism — what makes etifoxine different
Most clinical anxiolytics hit a single mechanism: benzodiazepines bind the BZ allosteric site of GABA-A; buspirone is a 5-HT1A partial ag…
Why this matters for cognitive + dependence profile
The α1 subunit of GABA-A mediates sedation, hypnosis, anterograde amnesia, and most of benzodiazepine abuse liability (Tan et al. 2011). …
Pharmacokinetics
- Tmax (parent etifoxine): ~2-3 hours oral. - Half-life (parent): ~6 hours. - Active metabolite: diethyl-etifoxine — produced by hepatic …
Plain-English summary
Etifoxine is an anxiolytic that hits the brain's main "off" signal (GABA) through two paths at once — a direct push on the receptor at a …
Research Protocols
Disclaimer: These are commonly discussed research protocols and not medical advice.
Peptide Interactions
mechanistically distinct; etifoxine sometimes used as short-term anxiolytic bridge during the 4-8 week SSRI titration window. No documented PK concerns. Comp…
different mechanism (NMDA modulation, GABA bumping, glutamine-transport inhibition); mild additive anxiolysis possible. Compatible.
different mechanism (NMDA glycine site, mineral status); compatible with no documented interaction.
HPA-axis cortisol normalization; different mechanism, compatible.
non-pharm anxiolytic; ideal stacking partner.
additive CNS depression possible despite cleaner monotherapy profile than benzodiazepines. French label advises avoiding alcohol during treatment. Hepatotoxi…
mechanistically overlapping (both enhance GABA-A tone, though via different binding sites). Not formally contraindicated but rarely justified — the entire ra…
additive hepatotoxicity risk given the etifoxine DILI signal.
etifoxine drives endogenous allopregnanolone synthesis; co-administration with exogenous neurosteroid analogs would produce additive GABA-A neurosteroid-site…
first-generation antihistamines (diphenhydramine, hydroxyzine), Z-drugs (zolpidem, zopiclone), opioids, gabapentinoids — additive sedation; compounds lethali…
GABA-B agonists with their own dependence + withdrawal pharmacology; stacking unjustified.
What to Expect
- Week 1Tolerability and dose-response.
- Week 2-4Early effect window.
- Week 4-8Peak benefit assessment.
- Week 8+Cycle decision point.
Side Effects & Safety 9
Side Effects
- 1Mild somnolence (~5-10%), particularly at treatment initiation
- 2Headache (~5%)
- 3Mild GI upset, nausea (~3-5%)
- 4Dizziness (~3-5%)
- 5Skin rash (mild, non-DRESS; usually self-limiting)
- 6Fatigue
- 7Sleep disturbance (paradoxical, less common than with benzodiazepines)
- 8Dry mouth
- 9Abdominal pain
When to Stop
- Idiosyncratic hepatotoxicity. Cottin et al. 2016: 99 cases over 1995-2015 in French pharmacovigilance database. Hepatocellular or mixed pattern, generally reversible on discontinuation, several cases of fulminant hepatitis. Not dose-dependent. Mechanism unclear (probably immune-mediated idiosyncratic reaction, similar to other rare-DILI signals). This is the principal safety concern with etifoxine. ANSM-mandated risk minimization measures include label warning, pharmacovigilance monitoring, and recommendation against use in known hepatic dysfunction.
- Severe cutaneous adverse reactions — DRESS (drug reaction with eosinophilia and systemic symptoms), Stevens-Johnson syndrome, toxic epidermal necrolysis. Very rare (~1/100,000 exposures); immune-mediated; fatal cases have been reported.
- Anaphylactoid reactions — rare; immediate hypersensitivity.
- Hyponatremia — rare; mechanism unclear.
- French label contraindicates pregnancy and breastfeeding. Limited human data; theoretical risk via TSPO-mediated steroidogenesis modulation in fetal development.
- First 4-8 weeks: primary hepatotoxicity-detection window. Baseline LFTs, then 4-week + 8-week recheck. Symptoms warranting immediate stop and hepatology eval: jaundice, dark urine, RUQ pain, unexplained fatigue or anorexia.
- First 2 weeks: primary cutaneous-reaction-detection window. Any rash with mucosal involvement, fever, or lymphadenopathy → STOP IMMEDIATELY (DRESS / SJS suspicion).
- Long-term (>3 months): less well-characterized. French label supports up to 12 weeks; chronic indefinite use is not formally evaluated.
References
Nguyen N, Fakra E, Pradel V, Jouve E, Alquier C, Le Guern ME, Micallef J, Blin O — Efficacy of etifoxine compared to lorazepam monotherapy in the treatment of patients with adjustment disorders with anxiety: a double-blind controlled study in general practice (Hum Psychopharmacol 2006, PMID 16634998)
foundational head-to-head RCT, n=191, etifoxine 150 mg/day vs lorazepam 1.5 mg/day, 28 days, double-blind. Non-inferiority on HAM-A; superior on day-35 post-treatment rebound; cleaner cognitive pro…
View StudyVerleye M, Akwa Y, Liere P, Ladurelle N, Pianos A, Eychenne B, Schumacher M, Gillardin JM — The anxiolytic etifoxine activates the peripheral benzodiazepine receptor and increases the neurosteroid levels in rat brain (Pharmacol Biochem Behav 2005, PMID 15823663)
foundational TSPO-mechanism paper. Demonstrates etifoxine drives de novo neurosteroid synthesis in rat brain (allopregnanolone, THDOC) and that anxiolytic effect is partially blocked by neurosteroi…
View StudyCottin J, Gouraud A, Jean-Pastor MJ, Dautriche-Pham A, Boulay-Coletta I, Vial T, Lagier G — Safety profile of etifoxine: A French pharmacovigilance survey (Eur J Clin Pharmacol 2016, PMID 26970743)
French national pharmacovigilance review of 99 hepatotoxicity cases reported 1995-2015. Idiosyncratic, not dose-dependent, generally reversible. Drove ANSM risk-minimization measures.
View StudyGirard C, Liu S, Cadepond F, Adams D, Lacroix C, Verleye M, Gillardin JM, Baulieu EE, Schumacher M, Bernard G — Etifoxine improves peripheral nerve regeneration and functional recovery (PNAS / Brain 2008)
animal sciatic-nerve-crush model; accelerated remyelination + functional recovery via Schwann-cell TSPO + neurosteroid synthesis. Foundational paper for the peripheral-nerve-regeneration off-label …
View StudySchlichter R, Rybalchenko V, Poisbeau P, Verleye M, Gillardin JM — Modulation of GABAergic synaptic transmission by the non-benzodiazepine anxiolytic etifoxine (Neuropharmacology 2000)
electrophysiology characterization of direct GABA-A PAM action at non-BZ site with β2/β3 subunit preference.
View StudyHamon A, Morel A, Hue B, Verleye M, Gillardin JM — The modulatory effects of the anxiolytic etifoxine on GABA-A receptors are mediated by the β subunit (Neuropharmacology 2003)
characterizes the β2/β3 subunit specificity of the direct binding site.
View StudyStein DJ — Etifoxine in PTSD-relevant fear-extinction paradigms (publication search)
examines neurosteroid-axis modulation by etifoxine in trauma-relevant paradigms; positions etifoxine within the broader allopregnanolone-deficiency hypothesis of PTSD pathophysiology.
View StudyChoi YM, Kim KH — Etifoxine for management of acute and chronic anxiety: a review (J Korean Neuropsychiatr Assoc 2018)
modern clinical review summarizing efficacy + safety profile.
View StudyANSM (Agence nationale de sécurité du médicament et des produits de santé) — Stresam (etifoxine) pharmacovigilance bulletins and risk minimization measures
French regulator's official risk-management documents covering hepatotoxicity and rare cutaneous reaction signals.
View StudyServier / Biocodex — Stresam (etifoxine HCl) French Summary of Product Characteristics (RCP)
French label / SmPC, official prescribing information.
View StudyLiu Y, Zhang LY, Wang XQ — Etifoxine: a comprehensive review on neuroprotective and analgesic properties (review 2020)
modern review covering peripheral nerve regeneration + neuroprotection literature.
View StudyChoi JH, Kim KS — Translocator protein (TSPO) ligands as potential therapeutics for anxiety disorders (review)
broader context on TSPO drug-development frontier.
View StudyBrexanolone (Zulresso) FDA approval and prescribing information (2019)
IV allopregnanolone for postpartum depression; same downstream GABA-A neurosteroid-site target as etifoxine's TSPO arm.
View StudyZuranolone (Zurzuvae) FDA approval and prescribing information (2023)
oral allopregnanolone analog for postpartum depression; same downstream target.
View StudyTan KR, Rudolph U, Lüscher C — Hooked on benzodiazepines: GABA-A receptor subtypes and addiction (Trends Neurosci 2011, PMC4020178)
α1-subunit-driven addiction biology; mechanistic context for why a non-α1-selective compound like etifoxine has cleaner abuse-liability profile.
View StudyHow was your experience with this compound?
Anonymous · one vote per session · results below at 5+ votes.
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