You will be shown an abstract from a biomedical research paper. Given this abstract, your task is to extract all unique entities of the following types: ["Chemical"].

Please return the output as a JSON object of the format: {"Chemical": ["Arsenic", ...]}. The keys should be entity types and values should be lists of extracted entities belonging to the corresponding type. If you cannot find entities belonging to a specific type, the value should be [].

Only output the JSON object and do not include any additional text.

Abstract:

Serial infusions of low-dose ketamine for major depression. Background: Single infusions of ketamine have been used successfully to achieve improvement in depressed patients. Side effects during the infusions have been common. It is not known whether serial infusions or lower infusion rates result in greater efficacy. Methods: Ten depressed patients were treated with twice weekly ketamine infusions of ketamine 0.5 mg/kg administered over 100 min until either remission was achieved or four infusions were given. Side effects were assessed with the Young Mania Rating Scale (YMRS) and the Brief Psychiatric Rating Scale (BPRS). Patients were followed naturalistically at weekly intervals for four weeks after completion of the infusions. Results: Five of 10 patients achieved remission status. There were no significant increases on the BPRS or YMRS. Two of the remitting patients sustained their improvement throughout the four week follow-up period. Conclusions: Ketamine infusions at a lower rate than previously reported have demonstrated similar efficacy and excellent tolerability and may be more practically available for routine clinical care. Serial ketamine infusions appear to be more effective than a single infusion. Further research to test relapse prevention strategies with continuation ketamine infusions is indicated.
{"Chemical": ["Ketamine", "ketamine"]}