A 70yearold woman presented to an acute inpatient rehabilitation facility on postoperative day three, after undergoing left total knee arthroplasty. Her past medical history included severe osteoarthritis, hypertension, and diabetes mellitus type 2 and was negative for any psychiatric illness. The patient took metformin, celecoxib, and oxycodone/acetaminophen prior to undergoing surgical intervention. After surgery, pregabalin, 50 milligrams twice a day, was added to her previous oral analgesic

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... regimen of celecoxib and oxycodone/ acetaminophen. However, on the night of admission postoperative day two (POD #2), she developed mild paranoia. Her husband and nursing staff reassured her the entire night. In the morning, she apologized for acting strangely and participated in all therapy sessions. All medications that could cause psychiatric disturbance or delirium, including oxycodone/acetaminophen and pregabalin, were discontinued. That night, however, her paranoia returned and she remained emotionally labile and delusional despite reassurance and delirium intervention. During the night, she pulled the fire alarm in order to have the police and fire department come to protect her.