Signals of Possibly Persistent Gustatory, Olfactory and Auditory Adverse Drug Reactions to Antibiotic Drugs: A Disproportionality Analysis Using the EudraVigilance Database

Background: In 2018, the European Medicines Agency issued some risk minimisation measures related to unresolved adverse drug reactions (ADRs) reported for fluoroquinolones, including sensory ADRs. Spontaneous reporting databases frequently report unresolved outcomes for gustatory, olfactory and auditory (GOA) ADRs. However, such a high volume of unresolved GOA ADRs could reflect an under-investigated clinical issue or an intrinsic difficulty in the outcome assessment. Objectives: The objectives of the study were: (1) to investigate whether unresolved outcomes are reported more frequently for GOA ADRs than for other ADRs to systemic antibiotics and (2) to identify possible signals of unresolved GOA ADRs for systemic antibiotics. Methods: We used the EudraVigilance database to extract the number of ADRs to systemic antibiotics of the Anatomical Therapeutic Chemical class J01 up to February 2019. We classified ADRs in "non-GOA ADRs" and "GOA ADRs". Adverse drug reactions were categorised in three groups according to the outcome: defined, persistent/permanent (unresolved) and undetermined ADRs. We performed disproportionality analyses with the case/non-case methodology, by calculating the crude reporting odds ratio (ROR) and 95% confidence interval (CI). Cases were all persistent/permanent ADRs, and non-cases were defined and undetermined ADRs. For the first objective, index groups were gustatory or olfactory or auditory ADRs, while reference group included all non-GOA ADRs. For the second objective, we performed a disproportionality analysis by using the sub-set of GOA ADRs. Index and reference groups varied with subgroups of drugs and drug class, so that each drug and drug class was compared with the others. We conducted two sensitivity analyses for each analysis by varying the case definition. Results: We extracted 748,798 ADRs, including 10,770 GOA ADRs. The first analysis showed that GOA ADRs were reported more frequently as unresolved events compared with all other ADRs (ROR: 2.68 95% CI 2.51-2.85; ROR: 5.20 95% CI 4.66-5.81; and ROR: 2.64 (95% CI 2.51-2.79, respectively). Gustatory ADRs were reported more frequently as unresolved for doxycycline (ROR: 1.69, 95% CI 1.18-2.41, p = 0.0038), azithromycin (ROR: 2.07, 95% CI 1.58-2.72, p < 0.0001) and levofloxacin (ROR: 1.59, 95% CI 1.22-2.07, p < 0.001) compared with GOA ADRs of all other antibiotics. Olfactory ADRs were reported more frequently as unresolved for doxycycline (ROR: 2.4, 95% CI 1.26-4.58, p = 0.0078) and levofloxacin (ROR: 1.92, 95% CI 1.28-2.86, p = 0.0014). Auditory ADRs were reported more frequently as unresolved for doxycycline (ROR: 1.52, 95% CI 1.09-2.12, p = 0.013) and clarithromycin (ROR: 1.31, 95% CI 1.09-1.59, p = 0.0049). Conclusions: We tested and used an appropriate expected frequency standard, which allows us to identify possible signals of unresolved GOA ADRs to antibiotic drugs in the EudraVigilance database. This approach could be used to generate signals of persistent or even irreversible events for other drugs or adverse reactions. However, these signals must be confirmed with a thorough clinical assessment.