A pilot study to identify correlates of intentional versus unintentional nonadherence to analgesic treatment for cancer pain.

Existing studies of medication adherence treat "nonadherence" as a monolithic concept. The goal of this study was to isolate correlates of intentional versus unintentional nonadherence for analgesic treatment for cancer pain. Patients were recruited from outpatient oncology clinics in the middle Atlantic region, ≥18 years old, and diagnosed with solid tumors, and had an active prescription of at least one around-the-clock analgesic. The Morisky Medication Adherence Scale (MMAS) was used to assesses "unintentional" (forgetfulness/carelessness) and "intentional" (stopping use of medication if feeling better or worse) dimensions of analgesic nonadherence. A visual analog scale was used to assess the percentage of analgesic doses taken in the preceding month. A majority of participants (85.5%) took prescribed analgesics in the index period. However, 51% reported taking only up to 60% of the analgesic doses prescribed to them. Stopping taking analgesics when feeling better was the most commonly reported nonadherence behavior (74%); those reporting "intentional" nonadherence when feeling better were more likely to report not using analgesics in the index week (100% vs. 67.7%; p = .029) and agree that pain medication can keep you from knowing what is going on in your body (p = .029) and were less likely to need stronger pain medication (33.3% vs. 81.5%; p = .003). "Unintentional" nonadherence, i.e., forgetfulness/carelessness, though associated with many analgesic beliefs, was not associated with measures of analgesic use in the index period. These preliminary data indicate that different heuristics underlie intentional versus unintentional nonadherence to analgesia and that intentional and unintentional nonadherence behaviors may have different implications for pain treatment outcomes.