1. The breakthrough cancer pain is a worsening stage of the underlying pain, rapid onset and limited duration (less than 45 minutes), in patients under opioid therapy. This pain may be due to the neoplastic disease itself, to other diseases or to the medication used to treat it ².

Constipation is considered a common side effect associated with opioid administration for pain management, which is usually moderate to severe and is associated with cancer or other chronic non-oncological conditions³.

The post-operative nausea and vomiting (PONV) is one the most frequent and unpleasant complications after general anesthesia for a surgical operation ⁴. Persistent or severe PONV can cause medical complications such as dehydration, electrolyte disturbances, and delayed patient bowel movements⁵. The overall impact of PONV, a determinant of patient outcome and satisfaction, has been reported to range from 10% to 79%⁶.

A device containing anesthetic is attached to the intravenous catheter or even to a subcutaneous catheter. When the patient is in pain, he presses a button and injects a dose of medicine intravenously. It is possible to adjust the dose and frequency of response to avoid overdose of the drug. This pump should only be used by the patient and not by another person in order to avoid unnecessary medication administration. The drugs commonly used in this technique are morphine, pethidine and fentanyl⁷. Some patients experiencing nausea, vomiting, pruritus, urinary retention and constipation following opioids administration⁸.

Acute pain is usually caused by an acute illness or injury. Typically, there is no psychological element. Therapeutic goals for acute pain begin with timely intervention, with immediate adjustments regarding treatment regimen for adequate pain control. Other goals include reducing pain to an acceptable level and facilitating recovery from the underlying illness or injury ^9,10

Chronic pain can be related to cancer or non-cancerous causes. Often there is a psychological component. Therapeutic goals of chronic pain include reducing pain and thus reducing patient’s suffering, improving their ability to cope with the development of self-help strategies, reducing dependence on health care systems and improving relationships (such as family, friends and health care professionals) ^9,10.