Avoidable hospitalizations due to adverse drug reactions in an acute geriatric unit. Analysis of 3,292 patients.

Objective: To determine prevalence of admissions due to an adverse drug reaction (ADR) and determine whether or not admission was avoidable, and what drugs and risk factors were implicated.

Design: Cross-sectional observational study.

Study Sample: All patients hospitalized in an acute geriatric unit during the period January 2001 to December 2010 were studied.

Measurement: To determine whether admissions were due toADR, we used the World Health Organization-Uppsala Monitoring Centre criteria and the Naranjo scale. Beers criteria were used to detect potentially inappropriate medication.

Results: A total of 3,292 patients (mean age 84.7 years, 60.1% women) were studied. Of these, 197 (6%) were admissions for ADR and nearly three quarters (76.4%, 152 cases) were considered avoidable admissions. The 5 most frequent drugs associated with admissions for ADR were digoxin, nonsteroidal anti-inflammatory drugs, benzodiazepines, diuretics and antibiotics. Independent risk factors for admissions for ADR were being female (OR 1.84; 95% CI 1.30-2.61), inappropriate medication according to Beers criteria (OR 4.20; 95% CI 2.90-6.03), polypharmacy (>5 drugs) (OR 1.50; 95% CI 1.04-2.13), glomerular filtration rate<30mL/min (OR 3; 95% CI 2.12-4.23) and sedative use (OR 1.40; 95% CI 1-1.91).

Conclusion: ADR were responsible for 6% of admissions to an acute geriatric unit, and over 75% of these admissions were considered avoidable. Associated risk factors were being female, inappropriate medication, polypharmacy, renal insufficiency and sedative use.