First, polypharmacy is defined by the World Health Organization (WHO) as "the practice of administering multiple medications concurrently or the administration of an excessive number of medications". Habitual among elderly patients, polypharmacy is considered "appropriate" in cases of concomitant pathologies or in complex medical situations in which prescribed medications respect recommendations. Inversely, it becomes problematic when one or more medications are inappropriately prescribed or when the anticipated benefit for the patient is not obtained. In any case, the ageing of the population and the health risks associated, means that polypharmacy is a major issue in terms of public health, quality of care and the efficiency of prescribing.
Through a literature review, we have identified different definitions of polypharmacy: concurrent - the medications are administered at the same time -, cumulative - the sum of different medications administered over a given period of time, usually three months – and continuous - medications taken for prolonged and regular periods. The medication threshold defining the existence of polypharmacy (5 or 10 or more medications) was then examined. Finally, the aims, scope of application, methods of construction and useable databases were specified for each indicator.
We tested the 5 indicators most frequently cited in the literature review on the prescription database IMS Health-Disease Analyzer, in order to compare the ability of the selected indicators to identify polypharmacy: 3 indicators represent concurrent polypharmacy and one, cumulative polypharmacy. To these we added a continuous polypharmacy indicator, also found in the literature and retained within the Paerpa programme framework. If the prevalence of polypharmacy varies according to the indicators and thresholds used, it is higher using cumulative and continuous polypharmacy indicators than with concurrent polypharmacy indicators. The cumulative polypharmacy indicator makes it possible to identify 95 % of polypharmacy situations.
In the end, the indicator to retain will depend mainly on what we want to observe and measure. For example, if it is to consider the negative consequences of excess medication for an individual, to remedy this, the cumulative indicators seem more appropriate. They do take into account each medication administered with its adverse effects. If we rather consider drug interactions that occur in someone's treatment, concurrent polypharmacy indicators seem better suited. Nevertheless, if we consider the therapeutic and financial burden for an individual with chronic diseases, we will rather use continuous indicators, which also identify in-depth treatments prescribed to patients.
In fact, these indicators are complementary, used together, they allow a broader vision of the use of medications.
Data collection methods to measure polypharmacy are varied: medical files, pharmaceutical registers, reimbursement data, patient interviews. The data collection method strongly determines the information that will be available: prescription or over the counter, posology and duration, delivery, reimbursement.
Available data sources also strongly determine the indicators which can be tested. The measurement of concurrent polypharmacy therefore requires information concerning the duration of administration for each drug, often difficult to obtain, and continuous polypharmacy indicators require longer periods of observation.
More often than not, only prescription drugs or reimbursed drugs are taken into account which under-estimates pharmaceutical consumption and the risks of interaction.
Interview by Anne Evans