60 patients ASA I-III, undergoing total hip arthroplasty were randomly assigned, into one of two groups, namely group E (n=30), where levobupivacaine will be administeral intrathecally ; and group N (n=30), where levobupivacaine plus nalbuphine will be administeral intrathecally. All patients will receive a standardized multimodal analgesic regimen, including a PENG block and PCA morphine. Morphine consumption during the first 24 hours postoperatively will be measured and additionally the investigators will record: Time of morphine first dose administration, NRS scores in static and dynamic conditions in 4 hours, 6 hours, 12 hours, 18 hours, 24 hours, 36 hours and 48 hours postoperatively, complications, patient satisfaction and duration of hospitalization.