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Drug Interactions a Danger for Patients Taking Antipsychotics: Presented at APA

By Charlene Laino

WASHINGTON, DC -- May 13, 2008 -- A significant number of patients with schizophrenia and bipolar disorder receive prescriptions for drugs that can interact negatively with antipsychotics, researchers said here at the 161st Annual Meeting of the American Psychiatric Association (APA).

Jeff J. Guo, PhD, Assistant Professor, University of Cincinnati College of Pharmacy, Cincinnati, Ohio, and colleagues used the Ohio Medicaid claims database to search for simultaneous prescriptions of antipsychotic drugs and other medications that are known to have potentially dangerous interactions with antipsychotics. The database contained 44,511 patients aged 18 to 65 years treated from 2000 to 2003.

Overall, 24.7% of patients with schizophrenia and 24.5% of patients with bipolar disorder received prescriptions for an antipsychotic and at least 1 other drug with known interaction potential by the same provider or pharmacy.

A total of 11.9% of patients with schizophrenia and 11.8% of patients with bipolar disorder received prescriptions for drugs with dangerous interaction potential by the same physician on the same day.

The most frequently prescribed potentially dangerous drug pairs included olanzapine, risperidone, and quetiapine.

Multiple regression analysis showed that patients receiving dangerous drug combinations were more likely to have comorbidities, including depression (P = .001), substance abuse (P = .0003), anxiety (P = .0003), hyperlipidemia (P = .008), and chronic obstructive pulmonary disease (P = .028).

Actual adverse events due to drug-drug interactions were uncommon, affecting only 1.7% of patients. Adverse events were defined as those having the potential for severe or life-threatening consequences, such as seizure and arrhythmias.

"Potential drug-drug interactions should be considered when prescribing antipsychotic drugs," Dr. Guo concluded.


[Presentation title: Analysis of Potential Drug-Drug Interaction Pairs Associated With Antipsychotics Among Medicaid Patients With Schizophrenia or Bipolar Disorder. Abstract NR7-042]

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