Increased suicide attempt rate among patients interrupting use of atypical antipsychotics

PURPOSE: The aim of the study is to investigate whether patients at risk to commit suicide could be identified based on their drug refill patterns. METHODS: Data for this study were obtained from the PHARMO system comprising drug-dispensing data linked to hospital discharge records. All patients aged 15-45 years, suspected to suffer from schizophrenia and exclusive users of olanzapine or risperidone were selected. The use of antipsychotics was converted into treatment episodes of uninterrupted use. Therapy non-compliance was defined as a drug holiday of at least 30 days. The follow-up started with a treatment episode of at least 90 days. Relative risks for suicide attempts and 95% confidence limits due to drug holidays were estimated using Poisson regression analyses. RESULTS: Of 603 patients, 33% interrupted treatment for at least 30 days. An increased suicide attempt rate was observed when comparing uninterrupted and interrupted drug use (20.0/1000 person years vs 72.1/1000 person years, respectively). A four-fold increased risk for attempting suicide among patients with drug holidays was found (RR adjusted for age and gender 4.2, 95% CI: 1.7-10.1) compared to patients without drug holidays. CONCLUSIONS: Patients who do not refill atypical antipsychotics in time can be identified in the pharmacy and are most likely those with an increased risk to commit suicide.