Clinical Weighting of Drug-Drug Interactions in Hospitalized Elderly

Abstract

Adverse drug reactions impact on patient health, effectiveness of pharmacological therapy and increased health care costs. This investigation intended to detect the most critical drug-drug interactions in hospitalized elderly patients, weighting clinical risk. We conducted a cross-sectional study between January and April 2014; all patients 70 years or older, hospitalized for >24 hr and prescribed at least one medication were included in the study. Drug-drug interactions were estimated by combining Stockley's, Hansten and Tatro drug interactions. Drug-drug interactions were weighted using a risk-analysis method based on failure modes, effects and criticality analysis. We calculated a criticality index for each drug involved in the drug-drug interactions based on the severity of the interaction mechanism, the frequency the drug was involved in drug-drug interactions and the risk of drug-drug interactions in patients with impaired renal function. The average number of drugs consumed in the hospital was 6 ± 2.69, involving 160 active ingredients. The most frequent were as follows: Furosemide, followed by Enalapril. Of drug-drug interactions, 2% were classified as contraindicated, 14% advised against and 83% advised caution during the hospital stay. Thirty-four drug-drug interactions were assessed, of which 23 were pharmacodynamic drug-drug interactions and 12 were pharmacokinetic drug-drug interactions (1 was both). The clinical risk calculated for each drug-drug interaction included heparins + non-steroidal anti-inflammatory drugs (NSAIDs) or Digoxin + Calcium Gluconate, cases which are pharmacodynamic drug-drug interactions with agonist effect and clinical risk of bleeding, one of the most common clinical risks in the hospital. An index of clinical risk for drug-drug interactions can be calculated based on severity by the interaction mechanism, the frequency that the drug is involved in drug-drug interactions and the risk of drug-drug interactions in an elderly patient with impaired renal function.