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This chapter discusses the special set of potential opioid-related complications. Objective signs and symptoms of chronic pain are hard to ascertain, whereas opioid use is associated with concrete signs and symptoms that may act as markers for opioid side effects. Most commonly, opioids produce constipation, nausea, vomiting, sedation, and respiratory depression. Any adverse effects from opioids may significantly limit therapy, and some can present with life-threatening consequences. Unfortunately, there are few predictors of which patients will experience which side effects and which particular opioids will produce them. It is sensible to expect side effects and to take preventive action. Since not all opioid-related toxicity can be predicted or prevented, patients should be closely followed with a high level of suspicion. Effective management includes anticipation of adverse effects when possible, use of preventive measures, and choosing the best medication with the optimum method of administration. Clear communication with the patient, family, or nurse to ensure prompt recognition and response to adverse effects is of utmost importance in order to recognize and prevent possible adverse effects of opioid treatment.

Constipation is the most common dose-dependent side effect of opioids. But unlike most other side effects, tolerance does not develop. Thus, constipation can be expected throughout the duration of opioid administration. Preventive therapy with cathartics and adequate fluid intake is a mainstay of therapy and should be offered at the time opioids are started and continued throughout opioid treatment. Stool softeners and bulking agents such as bran or psyllium derivatives alone will be inadequate because opioid-related constipation results from decreased gut motility. Therefore, active stimulating laxatives are effective and passive ones are not.

Severe constipation may respond to oral administration of naloxone, which is an opioid antagonist with specificity to bowel. Administration of oral naloxone has limited systemic bioavailability; however, it has increased concentration and efficacy in the gastrointestinal (GI) tract. Unfortunately, there is uncertainty about the dosing regimen. Opioid withdrawal has been observed when oral naloxone is administered at dosages exceeding 20% of the prevailing 24-hour morphine dose. It is suggested that initial individual oral naloxone doses should not exceed 5 mg. In our institution, we start with 1.6 mg to 2.4 mg taken orally (4 to 6 small ampules) every 4 hours until the first bowel movement, or for five doses. If ineffectual, we may try another series with a higher dose. However, constipation may be caused by factors other than opioids. Oral naloxone only works when the constipation is solely opioid-related.

Since constipation can be mitigated by direct effects of antagonists on the bowel, it is possible that opioids that are delivered without direct bowel contact induce less constipation. There is evidence that certain opioid products that are absorbed without contact to the GI tract, such as transdermal fentanyl, induce less constipation when compared with oral morphine at doses effecting the same degree of pain relief. A significant reduction in the use of laxatives has been reported. In ...

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