Does amoxicillin cause drowsiness or hyperactivity?

Uncommon to do that: That would be the first time someone has reported those symptoms to me, as a possible reaction to amoxicillin.

Highly unlikely: Amoxicillin usually does not cause hyperactivity or drowsiness. With that being said, any medication can cause any type of reaction in anyone. An interaction with another drug is also possible. Ask your doctor or pharmacist to review all of your medications.