Adverse drug reactions (ADRs) are responsible for 5 % of hospital admissions, but hospital re-admission induced by ADRs remains poorly documented.

The aim of this study was to estimate the rate of hospital re-admission and the factors associated with re-admission in the patients over the age of 65 years. Secondary, we described the characteristics of cases of ADRs leading to re-admission for drugs other than chemotherapy agents.

Data were extracted from hospital discharge summaries provided by the Department of Medical Information of Toulouse University Hospital. All patients over the age of 65 years admitted to the hospital in 2010 for an ADR, identified from ICD-10 codes, were selected. All subsequent admissions of members of this cohort within 1 year of discharge following the index admission were reviewed retrospectively. The risk factors associated with hospital re-admission for ADRs were analyzed. Medical records were used for descriptive analysis of re-admission due to drugs other than chemotherapy agents.

We found that 553 of the 1000 patients admitted for ADRs in 2010 were re-admitted to hospital within 1 year. Among them, 87 cases were re-admitted for ADRs (estimated rate of 87/1000 re-admission for an ADR within 1 year). A comparison of the patients re-admitted for ADRs (n = 87) with those of patients re-admitted for other causes (n = 410) suggested that only cancer increased the risk of re-admission for ADRs (OR = 7.69 [4.59–12.88] 95 % CI). ADRs due to the same drug combination were the suspected cause of repeat admission in half the cases (other than chemotherapy). Hospital re-admission was considered avoidable in four cases (22 %).

This study shows an estimated rate of re-admission for an ADR around 87/1000 within 1 year, and the same drug combination were the suspected cause of repeat admission in half the cases. At least, 11 % of cases were avoidable.