Informational only. Not medical advice.INFORMATIONAL PLATFORM ONLY — NOT MEDICAL ADVICE, DIAGNOSIS, OR TREATMENT
Informational only. Not medical advice.INFORMATIONAL PLATFORM ONLY — NOT MEDICAL ADVICE, DIAGNOSIS, OR TREATMENT
Head-to-head comparison of Fladrafinil and Hydrafinil (9-Fluorenol) — mechanism, side effects, legal status, and pricing.
Fladrafinil (CRL-40,941) is a non-peptide synthetic eugeroic and the bis(4-fluorophenyl)-substituted analog of adrafinil, retaining adrafinil's N-hydroxyacetamide group. Never approved or marketed as a pharmaceutical in any jurisdiction, it is sold exclusively as an unregulated research chemical. Added to WADA's S6 (Stimulants, non-specified) category on the 2026 Prohibited List, effective 1 January 2026.
Hydrafinil (9-fluorenol) is a non-peptide fluorene derivative and secondary benzylic alcohol (C₁₃H₁₀O, MW 182.22) investigated as a potential wakefulness-promoting agent structurally distinct from modafinil's diphenylmethyl-sulfinyl scaffold. It has no approved human indication and is not FDA-approved or approved by any regulatory body for human or veterinary use. Hydrafinil is listed as an S6.A Non-Specified Stimulant on the WADA Prohibited List; Section S6.A stimulants are prohibited in-competition only, so it is banned in-competition and athletes are subject to strict liability. It is sold online by research-chemical vendors for laboratory use only, not for human consumption.
Fladrafinil
Hydrafinil (9-Fluorenol)
Category
Legal Status
Mechanism
Side Effects
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Fladrafinil
No pricing data yet.
Check Fladrafinil prices →Hydrafinil (9-Fluorenol)
No pricing data yet.
Check Hydrafinil (9-Fluorenol) prices →COA corpus from Disclosed Labs — independently tested batches only.
Fladrafinil
2
COAs
99.6%
Avg purity
1
Labs
Hydrafinil (9-Fluorenol)
2
COAs
99.0%
Avg purity
1
Labs
No clinical trials for any therapeutic indication exist; no FDA approval has been granted. The only identified human data are: (1) a 2026 peer-reviewed pharmacokinetics/metabolism study for anti-doping purposes (Krug et al., Drug Testing and Analysis), which administered fladrafinil orally to healthy volunteers and confirmed metabolism to flmodafinil, flmodafinil acid, and flmodafinil sulfone; and (2) unverified patent-holder claims from 1984 describing oral 50 mg capsules for hypersomnia/psychasthenia with reported 'excellent results' over 2–8 weeks—this is not an independently published or peer-reviewed trial. Animal studies (mice/rats, intraperitoneal, 16–256 mg/kg) from the 1984 Lafon patent reported reduced barbiturate-induced sleep duration, increased spontaneous motor activity, reduced inter-group aggression, improved motor recovery following hypoxic stress, and prolonged amphetamine-induced stereotypy.
No human efficacy or safety trials have been conducted. The only human data is a 2021 pilot pharmacokinetic/analytical study (Knoop et al., PMID 34378339) in which three healthy male volunteers received a single 50 mg oral dose of hydrafinil, with urine collected up to 72 hours post-dose to characterize Phase I/II metabolites (hydroxylated, glucuronidated, sulfo-conjugated) for anti-doping detection purposes; this study was designed solely for metabolite identification and does not establish safety, efficacy, or a validated dose. In rats, a Cephalon Inc. drug-discovery program screened fluorene-derived compounds as candidate next-generation modafinil agents; one analog ('compound 15') showed wake-promoting activity attributed to an active metabolite ('compound 3'), though the published abstract does not confirm compound 3's identity as fluorenol or provide potency data.
Fladrafinil and Hydrafinil (9-Fluorenol) are both in the Cognitive category and may have overlapping mechanisms. Researchers should review both profiles carefully, understand the mechanisms of action, and monitor the relevant biomarkers when combining compounds in the same class. As always, consult a licensed healthcare provider before making any decisions about combining research compounds.
This platform provides informational tools only, not medical advice. This comparison is for educational purposes only. Consult a licensed provider.
Contraindications
Lab Testing
Disclosed Labs