AdrafinilvsModafinil

Adrafinil is a prodrug—it is pharmacologically inactive until metabolized by hepatic cytochrome P450 enzymes (primarily CYP3A4) and possibly esterases into modafinil (the active metabolite) and modafinilic acid (inactive byproduct). The conversion involves oxidation of the sulfinyl group. Once converted, adrafinil acts identically to modafinil: inhibition of the dopamine transporter (DAT), activation of orexin/hypocretin neurons in the lateral hypothalamus, increased histamine release from tuberomammillary nuclei, and elevation of norepinephrine and serotonin in cortical regions. The hepatic first-pass conversion step explains the delayed onset (45-60 minutes vs 20-30 for modafinil) and the concern about liver enzyme elevation and oxidative stress with chronic daily use.

Modafinil's exact mechanism is not fully understood but involves multiple neurotransmitter systems. It inhibits the dopamine transporter (DAT) with moderate affinity, weakly increasing synaptic dopamine levels without causing vesicular depletion. Modafinil activates orexin/hypocretin neurons in the lateral hypothalamus—the brain's master wakefulness system—which project to histaminergic tuberomammillary nuclei, noradrenergic locus coeruleus, and cholinergic basal forebrain. This increases histamine release (promoting cortical arousal via H1 receptors), elevates norepinephrine in the prefrontal cortex (enhancing attention and executive function), and modulates serotonin (5-HT) transmission. Unlike amphetamines, it does not cause significant vesicular catecholamine release or reverse monoamine transporters, which explains its lower abuse potential and lack of typical stimulant crash.