How do i switch from 50 mg. of zoloft to 10 mg. of lexapro ?

This varies: A common way would simply be to start 10 mg Lexapro and after a week or two, reduce Zoloft to 25 mg for 1-2 weeks, then stop. Depending on side effects and clinical symptoms, your doctor may modify to faster, slower, or a different medication. Drug interactions with other medications would also need to be screened.

Agree with Dr. S.: but would ask you if you are doing this without your doctor's knowledge as he/she would surely have given you a strategy for transitioning from zoloft to lexepro when it was prescribed.