Prevalence of pre-existing risk factors for adverse events associated with atypical antipsychotics among commercially insured and medicaid insured patients newly initiating atypical antipsychotics.

Background: Atypical antipsychotics (AA) differ from one another in their adverse event (AE) profiles. Patient-specific pre-existing risk factors for AEs, including comorbidities and concomitant medications, may render the use of certain AAs potentially inappropriate, and others relatively safer or more tolerable.

Objective: To quantify the prevalence of pre-existing risk factors for AEs and potential drug-drug interactions (DDIs) associated with AA treatment among patients with schizophrenia (SCZ), bipolar disorder (BD), or major depressive disorder (MDD) newly-initiating AA treatment.

Methods: Retrospective, observational study using US claims databases. Patients identified had newly-initiated on a single AA (1/1/2010-11/30/2011; index date), were aged 18-64 years, had insurance enrolment for 12 months pre- (baseline) and 1 month post-index, and had ≥1 medical claim with an ICD-9-CM diagnosis of SCZ, BD, or MDD during baseline. A comprehensive list of AE risk factors, including potential DDIs, was developed based on AA package inserts. Administrative claims-based identification algorithms flagged the presence of each medical risk factor during baseline and identified concomitant prescribing of medications (90 days pre- to 30 days post-index) potentially causing DDIs with AAs.

Results: Of 97,010 patients identified, mean age was 41.2 years and 66.7% were female. Among patients initiating AA treatment, prevalence of pre-existing AE risk factors were aripiprazole 32.2%; olanzapine 51.6%; ziprasidone 75.6%; quetiapine 77.4%; risperidone 82.5%.

Conclusion: Despite the availability of several AAs to treat psychiatric conditions, pre-existing AE risk factors can limit patient treatment options. Given inter-AA variability in risk factors, open access to AA may help to optimize appropriate prescribing.