Prescription sequence symmetry analysis for prescribing cascades involving the same adverse drug reaction.

Abstract

A prescribing cascade indicates the use of an additional medicine (marker) to treat an adverse drug reaction (ADR) by a first (index) medicine. Many studies focus on one medicine group that causes an ADR. This study aims to detect and assess the prevalence of prescribing cascades in patients with co-medication that could cause the same ADR versus patients who do not have this co-medication. Prescription Sequence Symmetry Analyses (PSSA) was used in a retrospective cohort study. PSSA assesses asymmetry in the distribution of patients receiving first an index followed by a marker medication and vice versa. The number of patients using an index medicine before the marker medicine were divided by the number of patients using a marker medicine before the index medicine (i.e., the sequence ratio). The prescribing cascades of interest were cardiovascular medication causing the ADR erectile dysfunction (ED) treated with phosphodiesterase inhibitors and different medication groups causing the ADR peripheral edema (PE) treated with high ceiling diuretics. The adjusted sequence ratio (aSR) and its 95% confidence interval (CI) were calculated (≥1 indicates a possible prescribing cascade).