Assessment of Medication Safety Using Only Dispensing Data

Abstract

Purpose of ReviewThe purpose of this review is to provide an overview of the published studies that have been used to generate evidence on the safety of medicine use when only medication dispensing data are available.Recent FindingsMedication dispensing databases are increasingly available for research on large populations, particularly in countries that provide universal coverage for medicines. These data are often used for drug utilisation studies to identify inappropriate medicine use at the population level that may be associated with known safety issues. Lack of coded diagnoses, to identify outcomes, and lack of data on confounders can limit use of these data in practice for medication safety assessment. To overcome these issues, studies have exploited the fact that symptoms of adverse effects of medications can be treated with other medications, for example antidepressants to treat depression or oxybutynin to treat urinary incontinence. The challenge of unmeasured confounding has been addressed by implementing self-controlled study designs that use within-person comparisons and provide inherent control for confounding. Prescription sequence symmetry analysis (SSA) is a within-person study design that has been demonstrated as a useful tool for safety signal generation in dispensing data.SummaryUsing medicine initiation as a proxy for the development of adverse events can help to generate evidence of the safety of medicines when only medication dispensing data are available. Careful consideration, however, should be given to the sensitivity and specificity of the proxy medicine for the adverse event and potential for time-varying confounding due to trends in medicine utilisation. Data-mining approaches using dispensing data have the potential to improve safety assessments; however, the challenge of unmeasured confounding with these methods remains to be investigated.

The New Era of Pharmacists in Ambulatory Patient Care

“…This is particularly useful with complex patients who have multiple prescribers and more than one condition requiring treatment. Medication dispensing databases are increasingly available for pharmacists on large populations, particularly in countries that provide universal coverage for medicines [28][29][30].…”

Use of negative controls in a prescription sequence symmetry analysis to reduce time‐varying bias

“…Currently among the 44 PSSAs that were assessed in two PSSA reviews, 7,8 only eight studies 6,9‐15 utilized a negative control index drug. One study identified a significant association between the negative control index drug and subsequent initiation of the marker drug, thus indicating bias.…”

Evaluation of the key prescription sequence symmetry analysis assumption using the calcium channel blocker: Loop diuretic prescribing cascade

“…Relevant to this research question, it could also be an indicator of inappropriate prescribing, that is, a prescribing cascade where an adverse event is treated with another drug rather than removing the cause for the adverse event. There has been an increasing number of publications using this methodology, with many more presented as conference abstracts that have yet to result in a published manuscript 4–6 …”

“…There has been an increasing number of publications using this methodology, with many more presented as conference abstracts that have yet to result in a published manuscript. [4][5][6] The PSSA uses a relatively simple design and computationally efficient approach. 5 Following a case-only design approach, the first step of the PSSA is to identify case-only patients who are those initiated on both an index and marker medication within a pre-specified exposure window (e.g., initiation of a marker drug within 365 days before or after index drug initiation).…”