How long will it take for dexedrine (dextroamphetamine) to take effect?

20 - 40 minutes: One you are at the right dose, stimulants suchg as Dexedrine (dextroamphetamine) work quickly to relieve symptoms of adhd. Typically, the benefit starts within less than a half hour. Duration of benefit depends on dosage and type of formulation used and can range from 2-3 hours to as much as 10-12 hours.

Dexedrine: Dexedrine (dextroamphetamine) is usually effective within 30 to 60 minutes (often sooner).