Background: Constipation is a frequent and underdiagnosed complication in patients with advanced cancer. Constipation in this population is multifactorial, but the use of opioids is one
of the main causes. The purpose of this retrospective study was to establish the association
between opioid type and laxative dose, as well as the contribution of other clinical factors in
advanced cancer patients admitted to a palliative care unit.
Methods: The records of consecutive patients admitted to the Acute Palliative Care Unit at
the Grey Nuns Hospital between December 1995 and January 1997 were reviewed. Criteria of
eligibility were the presence of cancer pain treated by opioids (oral and subcutaneous morphine
and hydromorphone, oral methadone), oral laxative treatment capable of achieving at
least one bowel movement every 3 days, and the absence of bowel obstruction or colostomy.
During period(s) of stable analgesic doses, the charts were reviewed for demographic and
clinical characteristics, average number of bowel movements, daily laxative doses, doses and
type of opioid, laxative/opioid dose ratio (LOR) (calculated by dividing the total laxative dose
by the total opioid dose), functional and cognitive status, food intake, and level of calcium,
albumin, and potassium.
Results: Forty-nine evaluable patients were identified. The LOR in patients receiving oral
opioids was 0.15 ± 0.19 vs. 0.18 ± 0.17 in patients on parenteral opioids (p > 0.2). The LOR in patients receiving methadone was 0.025 ± 0.027 as compared to 0.24 ± 0.23 in patients receiving morphine and 0.17 ± 0.13 in patients on hydromorphone (p < 0.0001). We found a strong association between LOR and abdominal involvement (p < 0.0006), opioid type (p < 0.0001), age (p < 0.0001), and female gender (p < 0.034). There were no significant correlation between LOR and functional status, cognitive status, food intake, and level of calcium or potassium.
Conclusion: We conclude that laxative dose needs to be titrated on an individualized basis.
The LOR is lower in patients receiving methadone and in those of male gender, younger age,
and absence of abdominal involvement.
