Fladrafinil (also known as CRL-40,941) is an experimental wakefulness-promoting compound closely related to modafinil and adrafinil. It has never been approved as a medication in any country, but it circulates in the nootropics market as an unregulated supplement. Chemically, it is the bis(p-fluoro) derivative of adrafinil, meaning two fluorine atoms have been added to the base adrafinil structure.
How Fladrafinil Relates to Modafinil
Modafinil is a prescription drug used to treat narcolepsy, obstructive sleep apnea, and shift work sleep disorder. Adrafinil was its predecessor, a prodrug that the liver converts into modafinil. Fladrafinil sits in the same chemical family but with a specific tweak: fluorine atoms attached to its two phenyl rings. Its full chemical name is 2-[bis(4-fluorophenyl)methylsulfinyl]-N-hydroxyacetamide, and its molecular formula is C₁₅H₁₃F₂NO₃S.
Adding fluorine to a drug molecule is a common strategy in medicinal chemistry. Fluorine can change how quickly a compound is absorbed, how long it lasts in the body, or how strongly it binds to its target. In fladrafinil’s case, the fluorine additions were explored during early drug development but the compound never advanced to human clinical trials or regulatory approval.
How It Affects the Brain
Fladrafinil appears to work the same way modafinil does: by blocking the dopamine transporter, the protein responsible for clearing dopamine from the spaces between neurons. When this transporter is blocked, dopamine lingers longer in the brain’s reward and alertness circuits, producing wakefulness and a mild sense of focus or motivation.
Rat studies published in the European Journal of Neuroscience tested fladrafinil’s fluorinated analogs head-to-head against modafinil. The fluorinated compounds slowed dopamine clearance by 50% or more, matching modafinil’s effect with no statistically significant difference. At a dose of 32 mg/kg, the fluorinated analogs actually raised dopamine levels slightly higher than modafinil at the same dose (increases of 308% and 279% above baseline, compared to a lower peak for modafinil). However, modafinil reached its peak activity faster and at a lower dose, while the fluorinated compounds needed higher doses to hit their maximum.
One notable difference: fladrafinil’s effects on dopamine levels faded more slowly. In the same rat studies, dopamine returned to near-normal levels about 40 minutes after the highest modafinil dose, while the fluorinated analogs kept dopamine at roughly 200% of baseline an hour after the final dose. This suggests fladrafinil may have a longer-lasting effect, though “longer-lasting” in a rat doesn’t translate directly to a predictable number of hours in a human.
How the Body Processes It
Like most drugs in this family, fladrafinil is processed by the liver. The liver uses a family of enzymes called cytochrome P450 to break down the compound through oxidation and other chemical reactions, ultimately converting it into water-soluble byproducts that the kidneys can excrete. This is the same enzyme system responsible for metabolizing modafinil, alcohol, and hundreds of other substances.
Modafinil’s elimination half-life (the time it takes for half the drug to leave your system) is roughly 12 to 15 hours. Fladrafinil’s half-life in humans has never been formally measured, since no controlled pharmacokinetic studies have been published. The slower dopamine offset seen in animal studies hints that it could last at least as long, but that remains speculative without human data.
Why It Has No Approved Use
Fladrafinil was originally developed by Lafon Laboratories, the same French pharmaceutical company that created adrafinil and modafinil. But while modafinil went on to gain FDA approval and become widely prescribed, fladrafinil was never submitted for regulatory approval anywhere. No published human clinical trials exist for the compound. It sits in a gray zone: cataloged in chemical databases like PubChem and recognized by drug classification systems, but without the safety and efficacy data that any regulatory agency would require before allowing it to be sold as a medicine.
This matters because the safety profile of fladrafinil is essentially unknown in humans. People sometimes assume that because modafinil is well-studied and generally well-tolerated, its chemical relatives must be equally safe. That reasoning doesn’t hold. Small structural changes to a molecule can dramatically alter how it behaves in the body, which organs it affects, and what side effects it produces. The fluorine atoms that distinguish fladrafinil could be pharmacologically trivial, or they could introduce risks that simply haven’t been documented.
How People Use It
Fladrafinil is sold online as a “research chemical” or nootropic supplement, typically in powder or capsule form. Users in nootropics communities report taking it for wakefulness, focus, and productivity, often comparing its effects to a milder or longer-lasting version of modafinil. Commonly reported doses in these communities range from roughly 30 to 80 mg, though these numbers come entirely from user experimentation rather than clinical research.
Because it is not an approved drug, fladrafinil is not scheduled as a controlled substance in most countries. In the United States, it occupies a legal gray area: not FDA-approved, not explicitly banned, but also not legally marketed as a dietary supplement (since it is a synthetic compound, not a vitamin, mineral, or herb). The World Anti-Doping Agency (WADA) prohibits all eugeroics (wakefulness-promoting agents) in competition, so athletes subject to drug testing should be aware that fladrafinil would likely trigger a violation.
Risks and Unknowns
The core problem with fladrafinil is that nearly everything known about it comes from animal studies and anecdotal reports. No human trials have established a safe dosage range, identified drug interactions, or measured effects on the liver, heart, or immune system over time. Modafinil itself, despite its relatively clean safety record, carries rare risks of serious skin reactions and has known interactions with hormonal contraceptives and several other medications. Whether fladrafinil shares these risks, amplifies them, or introduces entirely different ones is unknown.
Because fladrafinil is processed by the same liver enzyme system that handles many common medications, there is a real possibility of drug interactions. Anything that competes for the same enzymes could either increase fladrafinil’s concentration in the blood (raising the risk of side effects) or reduce the effectiveness of the other medication. Users who take prescription drugs of any kind are introducing an unpredictable variable by adding an unstudied compound to the mix.
The lack of quality control in the supplement market adds another layer of risk. Without pharmaceutical-grade manufacturing standards, the purity, dosage accuracy, and identity of what is actually in a given fladrafinil product can vary significantly between vendors and even between batches from the same vendor.