I wanted my son to try Sarcosine, but research here is stating that it doesn't help in combination with Clozapine - any experiences?

GM,
I was ready to push the purchase button, but did a little research and found out Sarcosine is not effective with Clozapine. Has anyone on here tried this and found this to be true? Does anyone know what would be a good supplement to help with cognitive impairment and Clozapine? My son could definitely use some help in this department.
Thank you, Jen