Background The use of multiple medications and/or the administration of more medications that are clinically indicated, representing unnecessary drug use (polypharmacy) increases the risk of non-adherence, adverse drug reaction and drug interaction. These problems are specially common and relevant in older hospitalised patients.

Purpose Analyse the prevalence of polypharmacy at hospital admission and at hospital discharge in a group of older patients, and how the hospital stay modifies this prevalence.

Materials and methods Patients enrolled in our retrospective study were hospitalised at the Internal Medicine Department during October 2010. Only Patients ³ 75 years old were enrolled. Polypharmacy was defined as the concomitant use of five or more medications and high-level polypharmacy was defined as concomitant use of ten or more medications. The following data were recorded for each patient: sociodemographic details, functional status, Charlson co-morbidity index (predicts the ten-year mortality for a patient who may have a range of co-morbid conditions), diagnoses at discharge, and treatments at hospital admission and discharge.

Results Of the 109 patients enrolled, 61 were women. The average age was 82,69±5,15 years. At admission, 29,4% of patients were independents. The average of Charlson index was 4,62±2,3. On average, the patients studied were taking 9,01±4,01 drugs at the time of hospital admission and 9,84±3,83 drugs at discharge. Hospitalisation led to a significant increase in the number medications (p=0,001). Polypharmacy on admission and at discharge was observed in 87,2% and 91,8% of patients, respectively; and 42,2% were taking ten or more different drugs at admission and 53,2% at discharge, existing statistically significant difference between high-level polypharmacy at admission and discharge (p=0,036).

Conclusions Our study confirmed a relatively high prevalence of polypharmacy in older hospitalised patients at the Internal Medicine Department. Hospitalisation led to a significant increase in the number of medications and in the prevalence of the high-level polypharmacy. The high prevalence of polypharmacy in elderly patients shows the need to reevaluate the pharmacotherapy during hospital stay.