25mg seroquel (quetiapine) causes me to be extremely lethargic and unable to keep mentally alert for over 12 hrs after use. Is this normal?

Speak to your doc. Drowsiness,is a common, short lived side effect from seroquel, (quetiapine) but are you also taking other drugs? More likely,,this a combined drug reaction. Call your prescriber today to,discuss this effect to determine if the benefits of this drug outweight this effect.