Med question | ADHD Information

I went to my doctor yesterday and was given script for ritalin 10mg.  Told me to take it 2 times a day. She told me if it helped but wasn't enough help that I could take 2 (20mg) twice a day. I took one this morning. About 30 minutes after taking it, I was so sleepy that i couldn't hold my eyes open. I went to sleep and slept for about 3 hours. Is this normal???  I am also taking augmentin for strep throat....and zoloft (50mg).  anybody else experience this the first time taking ritalin?