d-Cycloserine adjuvant therapy to conventional neuroleptic treatment in schizophrenia: an open-label study

D-cycloserine, a partial agonist at the strichnine-insensitive glycine site of the NMDA receptor complex, was tested as adjuvant treatment to conventional neuroleptics in chronic schizophrenic volunteers. The drug was administered, o.a.d., at the daily dose of 250 mg for six weeks. Mental status outcome measures were completed at the end of each week of treatment. The major finding was a deteriora of the patients' clinical condition, specifically of their psychotic symptoms. These preliminary results are discussed among others in view of d-cycloserine pharmacologic properties and recent findings on the interaction between NMDA agonists and dopamine system. This study, finally, suggests the need for a controlled dose-finding trial to establish the activity and a therapeutic "window" of this drug in schizophrenia.