Inclusion Criteria:  Informed consent. Scheduled for elective craniotomy for resection of supra-tentorial intracranial tumor that requires cranium sawing, dural opening and excision of tumor, under general anesthesia. Age 18 - 80 years. American Society of Anesthesiologists' physical status I-III. Body mass index (BMI) under 35 kg/m2.  Exclusion Criteria:  Pregnant or current breastfeeding patients. Patients unable to provide informed consent or in need of a legal authorized representative. Patients with neurological disorders preventing a good understanding of the pain numerical reporting scale (NRS) before surgery. Patients with pre-operative aphasia. Patients with chronic pain or chronic use of opioids. Patients with current alcohol or drug abuse. Expected delayed extubation. Patients with documented allergy to opioids or acetaminophen. Preoperative Glasgow Coma Scale <15.