“…In accordance with the effectiveness of opioid, studies indicate the morphine as the first drug to be administered to the patient in the critical phase of the illness to relieve his pain. [12,[24][25] However, the World Health Organization recommends that the analgesia directed to the patients without prospect of cure must obey clinical criteria, the intensity of the symptoms and the approach of "WHO's analgesic scale". [22] Concerning the analgesic scale, this is a proposal that adapted the use of analgesics according to the intensity of the pain, that must be evaluated by following three steps: the first one is directed to the treatment of mild pain, using non-opioid analgesics and anti-inflammatories; the second one is recommended for patients with moderate pain with the use of weak opioids, combined with non-opioid analgesics and adjuvants; and the third one is reserved for patients with severe pain, in which the weak opioids are replaced by the strong ones, like morphine, methadone, oxycodone and fentanyl, associated with non-opioid analgesics and adjuvants.…”