Frequency of medication errors in primary care patients with polypharmacy.

BACKGROUND: Chronic diseases affect more than half of the population ≥75 years of age in developed countries. Prescription medication use increases with age. Depending on definition, 25-80% of elderly are exposed to polypharmacy. Polypharmacy increases the risk of hospitalization, interactions and adverse drug reactions.
OBJECTIVE: To examine the frequency of medication errors in patients with polypharmacy treated in general practice.
METHODS: The medications of 169 patients with polypharmacy treated in 22 GP surgeries in Austria were analysed. The analysis identified (i) medication errors, including non-evidence-based medications, dosing errors and potentially dangerous interactions in all patients and (ii) potentially inappropriate medications (PIMs) in the subgroup of elderly patients (≥65 years).
RESULTS: The patients took on average 9.1±3.0 medications per day. The maximum, in one patient, was 20 medications per day. Some 93.5% had at least one non-evidence-based medication. On average, 2.7±1.66 medications per patient were found to be not indicated. At least one dosing error was found in 56.2% of all patients. One potential interaction of the most severe degree (category X interaction) was detected in 1.8% (n = 3) and two such interactions in 0.6% (n = 1). These combinations should have been avoided. Of the 169 patients, 158 were elderly (≥65 years). Of these seniors, 37.3% (n = 59) had at least one PIM according to the PRISCUS list for the elderly.
CONCLUSION: The frequency of medication errors is high in patients with polypharmacy in primary care. Development of strategies (e.g. external medication review) is required to counteract medication errors.