The Pharmaceutical Journal
Vol 277 No 7423 p476
21 October 2006

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Phase III data offer hope to patients with opioid-induced constipation

Phase III study data have shown that the selective peripheral opioid-receptor antagonist alvimopan can relieve the symptoms of opioid-induced constipation (OIC).

The 12-week study enrolled 518 patients suffering from non-cancer pain and with OIC symptoms, defined as having fewer than three weekly spontaneous bowel movements (SBMs) plus one or more bowel movement symptoms (incomplete evacuation, straining, hard/small pellets) for at least 25 per cent of bowel movements. Patients were then randomised to receive either alvimopan or placebo.

During the study, 72 per cent of patients receiving alvimopan 0.5 mg twice daily achieved a weekly average of three or more SBMs compared with 48 per cent in the placebo group. The change from baseline in the number of SBMs was also increased (3.5 versus 2.0 in the placebo arm). Both results reached statistical significance.

Importantly, there was no change in the dose of opioid required to achieve analgesia, indicating that alvimopan does not affect an opioid’s central pain-relieving effect.

Commenting on the study results, Beverly Collett, consultant in pain management and anaesthesia, Leicester Royal Infirmary, said: “Although opioid-induced gastrointestinal side effects are common during opioid treatment for chronic pain, few pain treatment guidelines include advice on their management. As a result, laxatives tend to be widely used in clinical practice, despite the fact that they do not target the underlying cause of opioid-associated constipation.

“Further, if adequate symptom relief is not achieved, some pain management guidelines suggest lowering the opioid dose, which may lead to suboptimal pain relief. This highlights the need for effective, targeted strategies for the management of opioid-induced GI side effects.”

The data were presented at the fifth congress of the European Federation of IASP (International Association for the Study of Pain) Chapters held in Istanbul last month.