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: ["Disease", "Chemical"].

Please return the output as a JSON object of the format: {"Chemical" : ["Naloxone", ...], "Disease" : ["Hypotensive", ...]}. 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:

Post-operative rigidity after fentanyl administration. A case of thoraco-abdominal rigidity leading to respiratory failure is described in the post-operative period in an elderly patient who received a moderate dose of fentanyl. This was successfully reversed by naloxone. The mechanisms possibly implicated in this accident are discussed.
{"Chemical": ["naloxone", "fentanyl"], "Disease": ["respiratory failure", "rigidity"]}