Constipation in cancer patients on morphine

Constipation is a significant problem in patients taking morphine for cancer pain. The aims of this study were (1) to assess the magnitude of constipation in this study cohort, (2) to analyse the constipation treatment strategies and (3) to look for evidence of inter-individual variation in both susceptibility to constipation and response to treatment with laxatives in this patient group.

This was an observational study carried out in a tertiary referral cancer hospital. Two hundred seventy four patients were recruited to the study. All had a diagnosis of cancer and were on oral morphine for cancer pain. The main outcomes measured were subjective patient assessment of constipation severity in the preceding week and laxative use. Patients were asked to grade constipation in the preceding week on a four-point categorical scale: “not at all” (grade 0), “a little” (grade 1), “quite a bit” (grade 2) and “very much” (grade 3). Laxative dose groups (LDGs) were developed to assess laxative dosing.

Constipation affects 72% of this cohort of patients. Constipation in this population is poorly managed. Eighty nine percent of constipated patients were on inadequate laxative therapy. Inter-individual variation in constipation on morphine exists: some patients do not experience constipation and do not need to take any laxatives, some patients do not experience constipation because they are taking laxatives and some patients experience constipation despite being on high dose laxatives. These three groups were compared in terms of cancer diagnosis, time on morphine, dose of morphine and other concomitant factors. No factor was identified to account for this inter-individual variation. Improvement in the clinical management of constipation is needed, with titration of laxatives according to individual patient need.

Constipation affects a large proportion of cancer patients taking oral morphine. Constipation in these patients is generally inadequately treated.