Antiemetic and analgesic-sparing effects of diphenhydramine added to morphine intravenous patient-controlled analgesia

An initial bolus of diphenhydramine 30 mg at anaesthetic induction followed by postoperative PCA with a 4.8:1, but not 1.2:1, diphenhydramine-morphine mixture provides an effective antiemetic efficacy without morphine-sparing effects.