Interaction risk with proton pump inhibitors in general practice: significant disagreement between different drug-related information sources.

AIMS: To compare information on drug-drug interactions (DDIs) reported on twostandard drug-related information sources (Summary of Product Characteristics andDrugdex system by Micromedex), by assessing the prevalence and predictors ofpotential DDI with proton pump inhibitors (PPIs) in general practice.METHODS: From the ''Caserta-1'' Local Health-Service database, 156 generalpractitioners (GPs) were recruited. From more than 180,000 individuals registeredon their lists, we selected patients receiving co-prescription of PPI andmedications at interaction risk, according to the Italian Summary of ProductCharacteristics (SPC) of PPI and Drugdex information, during the year 2003.Thereafter, we carried out a regression analysis to identify the predictors ofco-prescription at interaction risk with PPI, on the basis of the two informationsources. A number of analyses were performed to evaluate agreement on DDIinformation between the SPC of PPI and Drugdex.RESULTS: According to SPC and Drugdex, 324 (3.0%) and 958 (9.0%) patients,respectively, received co-prescriptions of PPI and potentially interactingmedications during the study period. PPI users'' age, type of medication andnumber of other drug prescriptions per month were independent predictors ofreceiving co-prescriptions at interaction risk, when considering only Drugdex.With regard to potential DDIs with PPI, a significant disagreement (P < 0.0001)between the two drug-related information sources, was shown through agreementanalyses.CONCLUSIONS: Potential DDIs with PPI are a common health issue in generalpractice. Estimates of prevalence and predictors of potential DDIs with PPIsignificantly changes according to the drug information source being used.