Modafinil's exact mechanism isn't fully understood. Likely involves dopamine reuptake inhibition, histamine elevation, and orexin signaling. The result: sustained alertness without classical stimulant feel.
Dose: 100-200mg in the morning. Don't dose past noon. Half-life is ~15 hours.
Caveats: Tolerance develops with daily use. Skin reactions are rare but serious. Headaches common. Not for chronic sleep replacement.