Use of non-opioid analgesics as adjuvants to opioid analgesia for cancer pain management in an inpatient palliative unit: does this improve pain control and reduce opioid requirements?

Abstract

Cancer pain is complex, and despite the introduction of the WHO cancer pain ladder, few studies have looked at the prevalence of adjuvant medication use in an inpatient palliative medicine unit. In this study, we evaluate the use of adjuvant pain medications in patients admitted to an inpatient palliative care unit and whether their use affects pain scores or opiate dosing. In this retrospective observational study, patients admitted to the inpatient palliative care unit over a 3-month period with a diagnosis of cancer on opioid therapy were selected. Data pertaining to demographics, diagnosis, oral morphine dose equivalent of the opioid at the time of discharge, adjuvant analgesics, nonsteroidal anti-inflammatory drugs (NSAIDs), and pain scores as reported by nurses and physicians were collected. Seventy-seven patients were eligible over a 3-month period, out of which 65 (84 %) were taking an adjuvant medication. The most commonly prescribed adjuvant was gabapentin (70 %). Fifty-seven percent were taking more than one adjuvant. There were more women in the group receiving adjuvants (57 vs. 17%, p = 0.010). Those without adjuvants compared with those on adjuvants did not have worse pain scores on discharge as reported by physicians (0.8 ± 0.8 vs. 1.0 ± 0.7, p = 0.58) or nurses (2.0 ± 2.7 vs. 2.1 ± 2.6, p = 0.86). There was no difference in morphine equivalent doses of the opioid in both groups (median (min, max); 112 (58, 504) vs. 200 (30, 5,040)) at the time of discharge; 75-80 % of patients had improvement in pain scores as measured by a two-point reduction in numerical rating scale (NRS). This study shows that adjuvant medications are commonly used for treating pain in patients with cancer. More than half of study population were on two adjuvants or an adjuvant plus NSAID along with an opioid. We did not demonstrate any benefit in terms of improved pain scores or opioid doses with adjuvants, but this could reflect confounding variables and physician choice. Larger prospective studies are needed to define the opioid-sparing effects of adjuvants. Adjuvant agents are used in over 80 % of those treated for cancer pain.