The relationship between opioid use and laxative use in terminally ill cancer patients.

The frequency of the use of laxatives, and the relationship between doses of laxatives and of opioid analgesia, were determined by a prospective study of 498 hospice inpatients with advanced cancer. Laxatives were required by 87% of patients taking oral strong opioids, 74% of those on weak opioids and 64% of those not receiving opioid analgesia. The form of the relationship appears to be hyperbolic, as suggested by the presentation of the results arranged by opioid quartile and by the improved correlation obtained by subjecting the opioid data to a logarithmic transformation. It is concluded that opioids account for about a quarter of the constipation found in terminally ill cancer patients in a hospice. However, the dose of laxative required is likely to be significantly higher if an opioid is being taken than if not. The form of the relationship between laxative and strong opioid doses is what might be expected from the mediation of opioid-induced constipation by opioid receptors.