Costs associated with adverse drug reactions in an older population admitted to hospital: a prospective cohort study

PurposeThis study examines healthcare costs associated with adverse drug reactions (ADR) in an older population admitted acutely to an Irish tertiary hospital.MethodsProspective cohort study involving older persons admitted to hospital with and without an ADR. Data was collected at baseline, during hospitalisation and post-discharge. Participants provided information on healthcare resource use three months before admission (baseline) and three months after discharge (follow-up). For each healthcare resource, unit costs were derived and applied. The average cost (standard deviation (SD)) associated with the hospital admission for the ADR and non-ADR are presented. In addition, baseline and follow-up care costs were compared using difference-in-difference analysis and presented with 95% confidence intervals (CI). Costs by preventability and severity of ADR are also presented.ResultsA total of n = 230 participants were included (n = 93 ADR and n = 137 without ADR). The average cost associated with hospital admission for an ADR was euro9538 (SD euro10442) and euro9828 (SD euro11770) for non-ADR. The additional follow-up costs (difference-in-difference) associated with the ADR was estimated at euro2047 (95% CI: -euro889 to euro4983). The mean incremental follow-up cost of definite preventable ADRs was estimated at euro1648 (95% CI: -euro4310 to euro7605), possible preventable ADRs euro2259 (95 CI: -euro1194 to euro5712) and unavoidable ADRs euro1757 (95% CI: -euro3377 to euro6890). The mean incremental follow-up cost associated with moderate severe ADRs was estimated at euro1922 (95% CI: -euro1088 to euro4932) and euro3580 (95% CI: -euro4898 to euro12,058) for severe ADRs. ConclusionADRs leading to hospital admission are associated with modest incremental healthcare costs during and three months after admission. Severe and possibly preventable ADRs were associated with higher costs.