Discontinuation Categories Underlying Gaps in Dispensing for Six Medication Groups.

Purpose: Accurately identifying medication discontinuations at scale is important for developing evidence about deprescribing. Gaps in dispensing often serve as proxies for discontinuation but are imprecise. We categorize reasons for gaps in dispensing to inform data-based methods to accurately identify medication discontinuations.

Methods: Using pharmacy dispensing data, we purposively sampled from a population of adults age 65+ with 2+ chronic conditions who experienced a 90-day gap in dispensing-with and without subsequent fills-of oral diabetes drugs, statins, proton pump inhibitors, drugs with anticholinergic properties, anticoagulants and antiplatelet drugs, or antihypertensives. We reviewed clinical documentation (e.g., visit notes, communications, medication orders) from last dispensing through the 90-day gap plus 120 days to classify dispensing gaps as true discontinuations (clinically intended) or non-discontinuations (no evidence of intent to discontinue), and then into subcategories. Medications with no documented explanation for the gap in dispensing and continued listing on the patient's medication list were classified as non-discontinuations.

Results: Of N = 1906 records reviewed, there were 1068 (56%) true discontinuations and 838 (44%) non-discontinuations. Subcategories within true discontinuations included provider intent to discontinue, provider substitutions, intentional stops followed by restarts, and agreeing with a colleague's or patient's decision to discontinue. Non-discontinuations included documented low adherence, changes in dose, changes in pharmacy formulary, and changes in drug formulation. Proportions of drugs in categories and subcategories varied by medication group.

Conclusion: Using gaps in dispensing as proxy measures for medication discontinuation may introduce bias through misclassification, and varied reasons for discontinuation may complicate causal interpretations.