Effect of Backward Medication Switching on the Risks of Adverse Events of Schizophrenia Patients Using Atypical Antipsychotics

   Many studies explore the effects of medication switching from second generation antipsychotic (SGA) to first generation antipsychotic (FGA), yet few exam the health effect of backward medication switching.  This study investigated whether backward medication switching (from SGA to FGA) and reduced dosages on SGA increased adverse events in outpatient schizophrenia patients treated by SGA in Taiwan.  This study applied a three-year historical cohort design and compared the risks of adverse events (outcome) in 2004, measured by emergency room and hospital admissions, of patients experienced backward medication switching or dosage reduction on SGA (exposure status) in 2003 with those who did not (control group).  This study was based on a national fixed cohort (census) of 12,107 patients who have ever received SGA during the study period and used hospitals as regular source of care during 2002-2004.  Most data were drawn from National Health Insurance claims provided by Department of Health.  Cox proportional hazards model for recurrent events using Prentice, Williams and Peterson total-time approach was applied to estimate the hazard ratio (HR) of adverse events by exposure status of the patients while controlling the covariates.  The results showed that backward medication switching in 2003 significantly increased the risk of emergency room or hospital admissions (HR=1.15, 1.00-1.31) in 2004.  Backward medication switching and reduced dosages on SGA might increase the risk of adverse events of the schizophrenia patients treated by SGA in Taiwan.

Key words: medication switching, antipsychotic, atypical antipsychotic, schizophrenia