Glutamatergic agents have recently been a focus of great interest to neuropharmacologists and clinicians.26,27 The efficacy of sarcosine and other GlyT-1 inhibitors, such as RG1678 in the treatment of schizophrenia, has been under investigation in recent years.28,29 It is considered that these compounds may have beneficial effects on the negative, affective, and cognitive symptomatology in schizophrenia. In the described patient, the hypomanic state occurred, which had not been previously noted and described in any patient taking sarcosine. Besides the direct excitatory effect of sarcosine, possible reasons for these symptoms may be related to the amino acid-induced potentiation of serotonergic transmission that was previously increased with venlafaxine, a selective serotonin and noradrenaline reuptake inhibitor (but at 75 mg per day acting as a selective serotonin reuptake inhibitor only) and olanzapine (which also has serotoninergic potential). We hypothesize that sarcosine may increase serotonergic and dopaminergic transmission in prefrontal lobes and also in the hippocampus, which are areas of key importance for negative, cognitive, and affective symptomatology and where NMDA receptor is present in high density. Hypomania presented here could be a result
