Objective: The relationship between chronic noncancer pain (CNCP) control and pain medication (analgesic) adherence has not been widely documented. The primary aim of this study was to evaluate the relationship between pain intensity and the degree of adherence to analgesic medication prescribed in pain clinics. There was also a special emphasis on the influence of polypharmacy on adherence.
Methods: A cross-sectional clinical survey was carried out in pain clinics across Spain. Demographic and clinical data were collected from patients: pain intensity, analgesic prescription and adherence, and the presence of concomitant medical conditions and treatments. The relationship between analgesic adherence and pain intensity was analyzed using correlations and propensity scores based on ordinal logistic regression. Correlates of pain intensity were explored using multiple linear regression.
Results: Data was gathered from 1407 patients; 1321 were eligible for analysis. Their mean (standard deviation) age was 61.6 (14.7) years and the majority (67.3%) were women. More than half (57.9%) received step 3 analgesics. Pain intensity was scored 5 out of 10 on average. Just 65.9% of patients were reported to not have missed any analgesic dose during the previous week. Pain intensity correlated negatively with analgesic adherence (r(s) = -0.151, p < 0.001). Moderate versus very intense pain was predicted in patients with 'good' and 'very poor' adherence, respectively. The presence of concomitant medications also correlated negatively with analgesic adherence (r(s) = -0.074, p = 0.007). However, few investigators reported such a negative effect of polypharmacy.
Limitations: Key limitations of this research are its cross-sectional design and the absence of an objective means of measuring medication adherence.
Conclusions: This study has shown that there is a small but significant inverse relationship between analgesic adherence and CNCP control, which has remained elusive to date and should be further evaluated. Polypharmacy also had a negative influence on adherence, although this was not acknowledged by all investigators.