Drug-drug interactions in the hospital

Abstract

Introduction Drug interaction screening programs are an important tool to check prescriptions of multiple drugs for potential drug-drug interactions (pDDIs). Several programs are available on the market. They differ in layout, update frequency, search functions, content and price. The aim of the current study was to critically appraise several interaction screening programs in the Department of Medicine of a Swiss public teaching hospital. Methods A drug interaction screening program had to fulfil minimal requirements (information on effect, severity rating, clinical management, mechanism and literature) in order to be admitted to the present evaluation. The 100 most frequently used drugs in the Cantonal Hospital of Baden, Switzerland, were used to test the comprehensiveness of the programs. Qualitative criteria were used for the assessment of the drug interaction monographs. In a precision analysis, 30 drugs with and 30 drugs without pDDIs of clinical importance were tested. In addition, 16 typical patient profiles were checked for pDDIs, using Stockley’s Drug Interactions as a reference. Results Out of nine programs included, the following four fulfilled the above mentioned criteria: Drug Interaction Facts, Drug-Reax, Lexi-Interact and Pharmavista. Drug Interaction Facts contained the lowest number of drugs and was therefore the least qualified program. Lexi-Interact condenses many DDIs into one group, resulting in less specific information, whereas Pharmavista and Drug-Reax offer excellent interaction monographs. In the precision analysis, Lexi-Interact showed the best sensitivity (1.00), followed by Drug-Reax and Pharmavista (0.83 each) and Drug Interaction Facts (0.63). The analysis of patient profiles revealed that out of 157 pDDIs found by all programs, only 18 (11%) were detected by all of them. No program found more than 50% of the total number of pDDIs. A further evaluation using Stockley’s Drug Interactions as the gold standard revealed that Pharmavista achieved a sensitivity of 0.86 (versus Drug Interaction Facts, Lexi-Interact and Drug-Reax with a sensitivity of 0.71 each) with an acceptable positive predictive value of 0.67. Conclusion In order to detect most pDDIs without causing too many false positive results, drug interaction screening programs should have a high sensitivity and a high positive predictive value. Pharmavista offers the highest sensitivity of the programs evaluated with a positive predictive value in an acceptable range. An increase in sensitivity is possible by the combination of two programs.