Refill rate of antipsychotic drugs: an easy and inexpensive method to monitor patients' compliance by using computerised pharmacy data

Purpose In the literature, noncompliance to medication in patients with schizophrenia ranges from 20 to 89%. There is an urgent need for reliable and valid techniques that measure compliance in antipsychotic drug treatment. In this study, we use pharmacy-dispensing records to assess compliance by calculating the refill rate of antipsychotic medication. Methods Refill rates of chronic antipsychotic drug users in 1999 and in 2000 were established by dividing the number of prescribed days by the total number of calendar days that the patient was registered in a pharmacy prescription records database. Results More than 50% of patients using an antipsychotic drug show a refill rate that is associated with medication compliance (0.9- 1.1). The number of daily antipsychotic drug intakes was associated with a divergent refill rate, more than once daily dosing was associated with a significantly elevated refill rate (p < 0.015). Conclusions The refill rate is a valuable addition to the small arsenal of objective compliance measurement tools. It is an easy to obtain and inexpensive way to estimate (non)compliance. We recommend future studies to medication use in both mental and physical disorders, in order to further specify the actual value of refill rates in clinical practice. Copyright (C) 2004 John Wiley Sons, Ltd.