Drug prescription patterns in schizophrenia outpatients: analysis of data from a German health insurance fund

The aim of this study was to investigate routine administrative data from a major German health insurance fund, Techniker Krankenkasse, which covers 5.4 million insured individuals. Using a retrospective cohort design, this study analysed data collected from patients with a hospital diagnosis of schizophrenia in 2003 (index hospitalisation) in order to evaluate prescription patterns of antipsychotic drugs.

Patients with an ICD-10 diagnosis of schizophrenia, at least one year prior membership with the insurance fund and a follow-up period of one year were identified. Results were standardised by age and stratified by the severity of their illness, defined by the number of hospital bed days during the three years preceding the index hospitalisation.

A total of 3,121 patients with schizophrenia (male 56.4%, female 43.6%) received 56 692 single prescriptions of antipsychotics. Of these, 35.4% of the prescriptions were for typical and 64.6% for atypical antipsychotics; 55% were for high-potency, 45% for low-potency typical antipsychotics. The most frequently prescribed drugs were olanzapine (26.6%), clozapine (21.3%) and risperidone (19%). There were no relevant gender differences concerning prescription patterns. During a 12-month follow-up period after the first hospitalisation, 1 372 patients (43.9%) were treated exclusively with an atypical antipsychotic, another 499 patients (16%) had a combination of an atypical plus a low-potency typical antipsychotic. Thus, basal therapy with an atypical was observed in 59.9% of our study population. Only 327 patients (10.5%) were treated exclusively with a typical antipsychotic. A total of 645 patients (20.7%) were treated with a combination of atypical plus typical antipsychotic. Changes of medication within one substance group occurred more often with typical antipsychotics (50%) as compared to atypical antipsychotics (25%).

At 60%, the proportion of patients in this study treated with atypical antipsychotics was surprisingly high. Of significant interest is the frequent prescription of clozapine (14%). The results are discussed in comparison to comparable studies from other countries.