Objective: The mechanism underlying the development of neuropsychiatric symptoms such as unconsciousness, abnormal behavior, delirium, hallucinations, and convulsions in influenza has not been thoroughly investigated. The relationship between drug administration and neuropsychiatric symptoms during influenza is also poorly understood. This study is the first pharmacoepidemiologic study focused on investigating the relationship between drug administration and neuropsychiatric symptoms.
Design: Cohort study
Methods: Study subjects were patients under 18 years old who had influenza during the 2006/07 season. We prepared two kinds of questionnaires for doctor and for patient's family, and carried out the survey between January and March, 2007. Using data from 9,389 patients, we analyzed the relationship between neuropsychiatric symptoms, such as delirium, unconsciousness and convulsion, and drug administration of acetaminophen and oseltamivir.
Results: Analysis of the relationship between delirium and drug administration provided hazard ratios of 1.55(p=0.061)for acetaminophen and 1.51(p=0.084)for oseltamivir. These hazard ratios, which were adjusted for risk factors by multivariate analysis of the proportional hazard model, showed an increasing tendency of delirium after administration of each drug. In patients who received oseltamivir, a high incidence of delirium was observed between 6 and 12 hours after onset of fever. Furthermore, delirium was found to develop in a shorter time following oseltamivir use than it did after acetaminophen use. There was no relationship between unconsciousness and acetaminophen administration, as demonstrated by a hazard ratio of 1.06(p=0.839). The incidence of unconsciousness increased significantly with oseltamivir use with a hazard ratio of 1.79(p=0.0389), and unconsciousness was found to occur in a short time after oseltamivir use.
Conclusion: The results obtained from this study suggest that there are increased risks of delirium and unconsciousness with drug administration. Further pharmacoepidemiologic studies for hypothesis testing are required to study the relationship between abnormal behavior and drug administration.