Greetings, and thank you for your question. Who at the Mayo clinic said this?? This is not true. Yes, there are potential side effects to these medications which have to be watched for very carefully, but there is no evidence in the research to show either medicine destroys brain tissue when used as prescribed.
I hope this alleviates your fears! These medicines, when used properly and under supervision, can be very helpful for those taking them, if given for the right reasons.
I hope this helps! Please let me know if I may be of further service.