Thoracotomy is an invasive surgical procedure, which is mainly performed in patients with pre-existing lung disease such as lung cancer or chronic obstructive pulmonary disease. Pain after thoracotomy is considered the most intense acute postoperative pain, adversely affecting the ability to cough, deep breathing, and lung function, resulting in respiratory complications and delayed recovery. The adverse effects can be further aggravated by occurrence of chronic post-thoracotomy pain.