Incidence of adverse drug reactions in adult medical inpatients.

This study was a prospective observational study of ADR occurrence and evaluation in adult internal medicine inpatients conducted over a 120-day period. Clinical pharmacists screened for ADRs at a county hospital in Indianapolis, IN. Patient information was reviewed on admission, every four days during hospitalization, and at discharge. ADRs occurring after hospital admission were assessed for causality, severity, pharmacological type (i.e., augmented pharmacology versus idiosyncratic reaction) and affected organ system. Nurse and pharmacist reports, incident reports, physician consults, patient transfers to critical care units, and serum drug concentration reports were additional means of ADR identification. Overall, 23.1% of patients experienced an ADR while 2.6% of the 11,702 drug exposures resulted in an ADR. Patients aged greater than 65 years (29.6% vs. 20.5% for younger patients) and females (26.2% vs. 20% for males) were at higher risk for ADR development (p < 0.05). Length of hospital stay was longer (13.3 days vs. 6.7 days; p < 0.05) and drug exposures more frequent for patients experiencing ADRs (p < 0.001). Furosemide elicited the most ADRs with 36 in 244 patient exposures (14.7%). Diltiazem, enalapril, heparin, trimterene/hydrochlorothiazide combination and captopril were also frequently implicated. ADRs were classified as mild (35.9%), moderate (52.6%), and severe (10.2%). Organ systems most commonly affected were the metabolic/hematologic (32.9%), gastrointestinal (17.8%), genitourinary (11.8%), and cardiovascular (10.5%). Over 30% of events were idiosyncratic reactions. ADR incidence was consistent with previous literature. Many frequently implicated medications were newer agents and the severity of events was less than previously reported.