Background: Lists of potentially inappropriate medications (PIM) in the elderly allow patients and drugs at risk of Adverse Drug Reactions (ADRs) or inefficacy to be identified. They can also help to improve quality of drug prescriptions. We hypothesized that PIM use is associated to more ADRs than other prescriptions. Methods: All ADRs registered by the Midi-Pyrenees PharmacoVigilance Center between 1st of January and 30th of June 2012 in patients >75 years were included. Data on patients (age, gender, Charlson comorbidity index), drugs (number, ATC classification, Laroche PIM classification) and ADRs (type, seriousness, mechanisms) were analyzed. Statistical analyses used Chi2 and Z tests. Results: Among the 923 ADRs recorded during the period of the study, 272 (29.5%) were in patients >75 years. Mean age was 83.5+/-5.5 years (extreme values: 75-102). Most of them (59%) were females. Mean Charlson index was 1.7+/-1.0 (0-5) per prescription. These 272 prescriptions involved 1775 drugs [mean value: 6.5 (+/-3.4) drugs per prescription] with 137 PIM (7.7%) found in 29 ADRs reports. Main MPI ATC classes were nervous (100, 73.0%), cardiovascular (24, 17.5%) and musculoskeletal (6, 4.4%) drugs. Main ADRs found with these 137 PIM were lymphatic and blood (mainly increased INR, anemia, hematoma, 69, 25.4%), nervous (mainly confusion, 48, 17.6%), cutaneous (39, 14.3%) and cardiac (mainly arterial hypotension, 28, 10.3%) ones. Among the 272 ADRs notifications, 29 (10.7%) were found to be related to MPI and involved mainly nervous and cardiovascular drugs. The sole factor associated to MPI was the number of drugs (P < 0.0003; but not age, gender or Charlson index). The sole factor associated to a MPI-induced ADR was the number of MPI (P < 0.0001; but not age or the total number of drugs received). Conclusion: Out of the ADRs reports registered in the Midi-Pyrenees Pharmaco- Vigilance Database for patients >75 years, 1 out of 12 drugs is potentially inappropriate. More drugs are prescribed, more the risk of MPI use increases. Finally, the number of MPI increases the risk of drug-induced ADR.
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