[Strong opioids and constipation]

In cancer pain therapy treatment with strong opioids is essential. However, it may be accompanied by the occurrence of various adverse effects. The most frequent and persistent side effect in the course of opioid treatment is constipation. It is mainly caused by linkage of the opioid to the peripheral mu-receptors in the bowel and may increase as a result of certain concomitant circumstances, such as poor intake of fluids or electrolyte disorder. Present research indicates that there is a relation between type of opioid and degree of constipation, i.e. treatment with transdermal fentanyl or methadone tends to cause less constipation compared to morphine or hydromorphone. The route of administration of morphine--oral vs. subcutaneous--does not seem to affect the incidence of opioid-induced constipation. Furthermore, prophylaxis and efficient control of opioid-induced constipation still fail to be part of the routine in pain treatment.