The purpose of the study is evaluate the analgesic efficacy and safety profile of the Cox-2 specific analgesic Etoricoxib (arcoxia®) when administrated pre and postoperatively for controlling pain in adult patients undergoing thyroid surgery. Patients will be followed up in the immediate postoperative period, during the first postoperative (POD) day and in POD 2, 3 and 7. It is expected that with the addition of Etoricoxib, patients will experience less pain during the overall postoperative period and also a better quality of recovery when compared with the traditional analgesic regimen.

Inclusion Criteria:

• age >18 and <70 years
• body weight within normal ranges
• ability to understand the use of pain assessment scales and the PCA device

Exclusion Criteria:

• known allergy to any of the drugs utilized
• contraindication to opioid and non-opioid analgesic drugs
• a history of bleeding disorders, peptic ulceration or anticoagulant use within the last month
• pregnant or breast-feeding patients
• history of known or suspected drug abuse or patients who had taken NSAIDs within 24 h prior to surgery