We present a case of a woman with diagnosis of schizophrenia in a stable mental condition treated with olanzapine and venlafaxine (started due to negative and affective symptoms) who started taking 2 g of sarcosine or placebo per day as a participant of the Polish Sarcosine Study (PULSAR; NLM identifier: NCT01503359),24 a 6-month randomized double-blind placebo controlled trial. After an initial improvement in the first 10 weeks, the patient developed hypomanic symptoms in the next 2 weeks and it was necessary to decrease the dose of venlafaxine or sarcosine/placebo. Initially, information on whether the patient was in a study or a control group was concealed. Therefore, we decided to decrease the dose of antidepressant. We reduced the dose of venlafaxine by half, and after 7–10 days we observed mood stabilization without secondary depressive episode. The patient continued participation in the trial. Standard unblinding procedure revealed that the patient had been taking sarcosine throughout the course of the study. This case with recently published observations indicates the need for revision of the recommended dosage of sarcosine or concomitant drugs in patients
