How long does prozac (fluoxetine) 20mg take to have an effect if i have been taking concerta 36 mg for a month and previously on adderall ir15mg 1month ?

Prozac (fluoxetine) : Much different then the prior two meds. It takes a good 3-4 weeks to see full effects. And the drug levels need to build up in your body. So don't expect to take the med and feel something. Like the adderall (dextroamphetamine and racemic amphetamine). But take it regularly and I've it a chance. also talk with your doctor if things don't seem to be working

Inattention Meds: Usually serotonin inhibitors, like Prozac, (fluoxetine) take about 4-5 weeks to reach full peak effect.