Drug-Drug Interactions Associated with Length of Stay and Cost of Hospitalization

To evaluate the prevalence of drug-drug interactions (DDI) in hospitalized patients and to identify associated risk factors. Methods A retrospective cross-sectional analysis of prescription data and medical records from a public hospital in Brazil was conducted to identify potential DDI. Inappropriate drug combinations were identified and classified with a standard drug interaction source. Primary diagnoses were classified with Charlson Comorbidity Index (CCI). Sex, age, polypharmacy and length of stay, among other variables, were correlated with the frequency of potential DDI. Results The study included 589 patients and 3,585 prescriptions. Thirty-seven percent of the patients were exposed to at least one potential interaction during their stay in the hospital. The most frequent interacting pair was Digoxin+Furosemide (11%). In univariate analysis, several variables were associated with DDI, including sex, age, number of prescribed drugs, length and cost of hospitalization and CCI. Multivariate analysis showed that the adjusted odds of being prescribed a potential DDI among patients in polypharmacy was almost five-fold that of patients taking fewer than five drugs. Further, length of stay, CCI and cost of hospitalization were independently associated with DDI. Conclusion Analysis of prescription data found that a substantial number of potential DDI were identified. Results of this study indicate that DDI is associated with number of prescribed drugs, increased duration of stay in the hospital and cost, which suggests that DDI are a significant clinical and economic problem. Potential harm to patients could be avoided.