Concealed renal insufficiency and adverse drug reactions in elderly hospitalized patients.

BACKGROUND Adverse drug reactions (ADRs) are common causes of in-hospital complications for elderly people. The purpose of the present study is to verify whether concealed renal insufficiency, that is, reduction of the estimated glomerular filtration rate (GFR) in people with normal serum creatinine levels, is a risk factor for ADRs in elderly hospitalized patients. METHODS We used data on 11,687 hospitalized patients enrolled in the Gruppo Italiano di Farmacovigilanza nell'Anziano study. The outcomes of the study were any ADR, ADR to hydrosoluble drugs, and ADR to any other drug during the hospital stay. We compared 3 groups: normal renal function (normal serum creatinine levels and normal estimated GFRs), concealed (normal serum creatinine levels and reduced estimated GFRs), or overt (increased creatinine levels and reduced estimated GFRs) renal insufficiency. The relationship between renal function and ADR was evaluated using contingency tables and multiple regression analysis including potential confounders. RESULTS Concealed renal insufficiency was detected in 1631 (13.9%) patients and was frequently associated with male sex and poor nutritional status. Hydrosoluble drugs were responsible for 301 of the 941 recorded ADRs. After adjusting for potential confounders, both concealed (odds ratio [OR], 1.61; 95% confidence interval [CI], 1.15-1.25) and overt (OR, 2.02; 95% CI, 1.54-2.65) renal failure were associated with ADR to hydrosoluble drugs, but not with ADR to other drugs (OR, 0.83 [95% CI, 0.65-1.08], and OR, 1.01 [95%CI, 0.83-1.23], respectively). CONCLUSION Older hospitalized patients frequently have impaired renal function despite normal serum creatinine levels and are exposed to an increased risk of ADRs to hydrosoluble drugs.