Analgesic Adherence Rate
To report the analgesic adherence rates, 6 studies presented a percentage [3,4,12,13,15] and all but 1 highlighted the barriers associated with poor adherence [3,4,12,13,15,16].
The results of a pilot study exploring intentional and unintentional adherence revealed that 85.5% of patients took the prescribed medications in the previous week. Further analysis using visual analogue scale for dose adherence found that that 51% took up to 60% of the prescribed medications . In an exclusively African-American sample, the adherence rate was reported as 46% . Another study by Meghani et al compared adherence to prescribed ATC analgesics between African Americans and whites with cancer-related pain using an electronic monitoring system . The overall adherence rate for African Americans was 53% and 74% for whites . The authors concluded that there was a significant difference between the analgesic adherence rates between African Americans and whites in this study. On sub-analysis, analgesic adherence rates for African Americans were much lower for weak opioids (34%) and higher for long-acting opioids (63%).
In a study of individuals from an outpatient supportive care center with a majority white sample (74% Caucasian), overall 9.6% of patients deviated from the opioid regimen, while approximately 90% reported high adherence . It is important to note that a convenience sample was used here. Of the total 19 patients that deviated from the regimen, 11 used less opioids than prescribed and 8 used higher doses. Upon analysis, the opioid deviation was more frequent in males and non-whites. However, statistical analyses of the magnitude of deviation from prescribed dose and non-white racial/ethnic background were not reported. Within the “non-whites” category, the race/ethnicity is defined as African American (16%, n = 32) and “other” (9%, n = 18). The authors contend that this strong adherence resulted from a strong understanding of the regimen as evidenced by a high agreement between the prescribed dose and the patient reported prescription . Nguyen et al  argue that the literature shows that lower adherence rates for minority patients may be explained by the presence of comorbidities and lack of insurance.
Two other studies reported adherence rates for separate insurance cohorts [3,14]. The Medicaid cohort was younger and had a higher percentage of African-American individuals. However, in the self-pay/charity care group, the majority was Hispanic . In the pilot study, the differences between the groups on adherence with prescribed medication regimens did not achieve statistical significance. The data were summarized to suggest that nonadherence was more likely in the self-pay/charity care group and more follow-up visits occurred after discharge . During the larger retrospective study there was no difference in number of patients adhering to the regimen at each follow-up visit in each benefit group. The study concluded that the long-acting opiate adherence was influenced only by the benefits of use and that race/ethnicity was not a statistically significant predictor .
Factors Associated with Adherence
Multiple studies investigated factors underlying reported analgesic adherence rates for the ethnic and racial groups studied. Both clinical and sociodemographic variables were associated with analgesic adherence ( Table 4 ). These included cancer type and disease stage [3,4,13,14], pain intensity [3,4,13–16], side effects [13,15], type of analgesic prescribed [3,4,13–16], income/socioeconomic status [3,13,14], behavioral history [3,12,13], gender [3,4,12–16], and perceived barriers [3,4,13,15,16].