Categorisation of Pharmaceutical Adverse Events Using the Japanese Adverse Drug Event Report Database: Characteristic Adverse Drug Events of the Elderly Treated with Polypharmacy.

BACKGROUND: Pharmacokinetics and pharmacodynamics of drugs in elderly individuals differ from those in younger adults; thus, adverse drug events (ADEs) are common in older patients with polypharmacy because co-existing comorbidities elevate the risk of ADEs occurring. However, ADEs have not yet been characterised based on the elderly patients of Japanese origin and polypharmacy. OBJECTIVE: The 100 most commonly reported ADEs were grouped into four classes (Class 1-Class 4) based on elderly patients with polypharmacy. PATIENTS AND METHODS: In this study, logistic regression analysis was performed using cases recorded in the Japanese Adverse Drug Event Report (JADER) database. RESULTS: ADEs in elderly patients treated with polypharmacy-in whom the risk of electrolyte abnormalities, renal and respiratory disorders, and coagulopathy was high-were categorised as 'Class 1 [E(+), P(+)]', while ADEs in elderly patients not treated with polypharmacy-in whom the risk of delirium and fall was high-were categorised as 'Class 2 [E(+), P(-)]'. When there was no association with being elderly, ADEs associated with polypharmacy that carried a high risk of myelosuppression and infection were categorised as 'Class 3 [E(-), P(+)]', and allergic ADEs that were not affected by being elderly or polypharmacy, were categorised as 'Class 4 [E(-), P(-)]'. Class 1 events as well as Class 3 ADEs occurred more frequently in females than in males, whereas Class 3 ADEs (deep vein thrombosis and pulmonary embolism) occurred more frequently in males. CONCLUSIONS: Class 1 and Class 2 ADEs should be investigated in analyses that focus on individual drugs.