Abstract: The present invention describes a pharmaceutical composition at a fixed dose of paracetamol and specifically amitriptyline supported by the pharmacological interaction and safety studies that show its synergy for the anti-allodynic, the mechanical anti-hypernociceptive effects and for the reduction of persistent pain, proportions, safety and neuroprotective capacity. This is aimed to the treatment of mixed pain due to cancer that can be incorporated as another option in the strategy of the WHO analgesic ladder at step 1 for the treatment of mild pain. However, it can also be included in higher steps associated with opioids for the treatment of pain of greater intensity and potentially decrease the escalation of its doses and adverse effects such as tolerance and hyperalgesia.