It appears to involve more primitive aspects of the brain, activating deep structures that may block pain at a spinal level — similar to how opioidanalgesics work.
Methods: Using three ladders pain analgesic WHO introduced, that is the first ladder giving NSAIDs. The second weak opioid 'analgesics, the third strong opioidanalgesics.
Opioidanalgesics are the mainstay for treatment of moderate and severe pain. However, the clinical use of opioid drugs still faces many obstacles, such as side effects and analgesic tolerance.