Usefulness of Acetaminophen Associated With Strong Opioids for Acute Pain in Cancer Patients

Cancer pain is one of the most frequent and relevant symptoms in cancer patients and has a great impact on a patient's quality of life. International and local standards recommend as an initial strategy, the use of an analgesic scheme composed of strong opioids (morphine, methadone or fentanyl) associated with adjuvants such as paracetamol, based upon the assumption that the use of combined analgesics could have a better analgesic effect, could allow the use of lower dose of opioids and that also could prevent the occurrence of adverse effects of opioids. However, there is uncertainty about the impact of paracetamol as an adjuvant in patients who use strong opioids for pain management in cancer patients with moderate to severe pain. To clarify this question, this study aims to evaluate the efficacy and safety of intravenous paracetamol associated with strong opioids in hospitalized cancer patients who have pain associated with cancer of moderate to severe intensity, (4 or more), older than 18 years. Randomized double-blinded controlled study comparing intravenous acetaminophen 1 gr 4 times a day versus placebo for 48 hours as an adjuvant to strong opioids. We will assess pain intensity as a primary outcome validated assessments that estimate Verbal Numerical Rating Scale (VNRS) analogous verbal pain from 0 to 10, and de visual Analog Scale (VAS). We estimated that a decrease of 1 point on the verbal numerical scale would be statistically significant. In addition, the investigators will calculate the amount of total opioid dose in 24 hours and then perform the intervention. As a secondary outcome, adverse effects such as drowsiness, constipation, nausea and vomiting would be evaluated