Somnolence effects of antipsychotic medications and the risk of unintentional injury.

PURPOSE

This study examined the relationship between antipsychotic medications, categorized by published somnolence effects, and unintentional injury (UI).

METHODS

The study population included patients of 18-64 years of age in a healthcare insurance database with claims from 2001 to 2004 and diagnoses of schizophrenia or affective disorder. A nested case-control design was used with cases defined by an E-code claim (a specified external cause of injury) for selected UIs. For cases, the index date referred to the first injury. For controls, the "control index date" was the date of claim if there was only a single medical claim; for patients with > or =2 claims, one was selected at random as the "control index date." Both groups had a prescription for a first-generation antipsychotic (FGA) or second-generation antipsychotic (SGA) overlapping the index date. Potential somnolence effects were defined as: low (referent)--aripiprazole/ziprasidone; medium--risperidone; high--olanzapine/quetiapine: or any single FGA. Logistic regression models were used to estimate odds ratio (OR) and 95% confidence interval (CI) for UI, adjusted for gender, age, concomitant drug, and psychiatric diagnosis.

RESULTS

Among 648 cases and 5214 controls, high-somnolence SGAs were associated with an OR of 1.41 95%CI (1.03-1.93) for risk of UI, while medium-somnolence SGAs, and FGAs had ORs of 1.17 95%CI (0.83-1.64) and 1.17 95%CI (0.79-1.74), respectively. When quetiapine and olanzapine were disaggregated, ORs were 1.61 95%CI (1.15-2.25) and 1.25 95%CI (0.89-1.74), respectively.

CONCLUSIONS

High-somnolence SGAs may lead to UI among patients. When prescribing antipsychotics, clinicians should consider potential somnolence.