My father ,74, had knee replacement on March 21. He came home Saturday. His pain level in about 3 during the day, higher as he exercises. He doean t tolerate pain medication very well, but after trying morphine and something else, settled on Hydrocodone-acetaminophen 10-325. He took that while in the hospital and rehab hospital, although inconsistently. It took care of the pain for the first 2 hours only and he felt miserable on it (he was very irritable and jumpy, and his eyes looked wild and vacant) At home saturday, he took 1 Hydrocodone at 6pm and 1000mg acetaminophen at 10 pm for pain. At 2am he had sweat so profusely that we had to change the sheets. It happened again a few hours later to a lesser degree. Today, Sunday, he again had no pain meds during the day, same pain levels as Saturday. He took 1000mg acetaminophen at 9pm before bed and was in pain, so took another 1000mg at 1pm. At 3am he broke out in a sweat and soaked the sheets. His temperature and BP are normal. Any idea what s happening?