Continued potassium supplementation use following loop diuretic discontinuation in older adults: An evaluation of a prescribing cascade relic

The use of a new medication (e.g., potassium supplementation) for managing a drug-induced adverse event (e.g., loop diuretic-induced hypokalemia) constitutes a prescribing cascade. However, loop diuretics are often stopped while potassium may be unnecessarily continued (i.e., relic). We aimed to quantify the occurrence of relics using older adults previously experiencing a loop diuretic-potassium prescribing cascade as an example. We conducted a prescription sequence symmetry analysis using the population-based Medicare Fee-For-Service data (2011-2018) and partitioned the 150 days following potassium initiation by day to assess the daily treatment scenarios (i.e., loop diuretics alone, potassium alone, combination of loop diuretics and potassium, or neither). We calculated the proportion of patients developing the relic, proportion of person-days under potassium alone, the daily probability of the relic, and the proportion of patients filling potassium after loop diuretic discontinuation. We also identified the risk factors of the relic. We identified 284,369 loop diuretic initiators who were 8 times more likely to receive potassium supplementation simultaneously or after (i.e., the prescribing cascade), rather than before, loop diuretic initiation (aSR 8.0, 95% CI 7.9-8.2). Among the 66,451 loop diuretic initiators who subsequently (≤30 days) initiated potassium, 20,445 (30.8%) patients remained on potassium after loop diuretic discontinuation, and 9365 (14.1%) patients subsequently filled another potassium supplementation. Following loop diuretic initiation, 4.0% of person-days were for potassium alone, and daily probability of the relic was the highest after day 90 of loop diuretic initiation (5.6%). Older age, female sex, higher diuretic daily dose, and greater baseline comorbidities were risk factors for the relic, while patients having the same prescriber or pharmacy involved in the use of both medications were less likely to experience the relic. Our findings suggest the need for clinicians to be aware of the potential of relic to avoid unnecessary drug use.