Siskind DJ, Lee M, Ravindran A, et al. Australian & New Zealand Journal of Psychiatry.  Published online May 6 2018. https://doi.org/10.1177/0004867418772351

This systematic review of 46 studies of 25 interventions found that the best evidence is for the use of aripiprazole, fluoxetine and sodium valproate as augmentation agents for total psychotic symptoms and memantine for negative symptoms. Studies were limited in quantity and quality.

http://journals.sagepub.com/doi/abs/10.1177/0004867418772351