Postoperative analgesia for supratentorial craniotomy

INTERVENTION: Participants are allocated to one of four groups. All patients receive morphine‐based patient controlled analgesia for 24 hours following surgery, in addition to one of the following: 1. Intravenous dexketoprofen (50mg) 2. Intravenous paracetamol (1g) 3. Intravenous metamizol (1g) 4. Intravenous saline (0.9%) (placebo) CONDITION: Post‐supratentorial craniotomy pain ; Signs and Symptoms ; Acute pain PRIMARY OUTCOME: Pain intensity is assessed during the first 24 hours post‐surgery using the visual analogue scale (VAS) (at the 10th minute, 1, 2, 6, 12, and 24 hours postoperatively). SECONDARY OUTCOME: Assessed during the first 24 hours post‐surgery (at the 10th minute, 1, 2, 6, 12, and 24 hours postoperatively):; 1. Morphine consumption; 2. Morphine‐related side effects; 3. Ramsay Sedation Scale (RSS) ; 4. Blood pressure; 5. Heart/respiratory rate INCLUSION CRITERIA: 1. American Society of Anesthesiology (ASA) classification I‐II or III 2. Aged 18 ‐ 70 2. Scheduled for elective supratentorial craniotomy