Antipsychotic polypharmacy and associated phenomena in patients with schizophrenia: Rational or irrational?

Abstract

A review of the literature of psychopharmacological studies reveals that there are great discrepancies in reported rates of psychotropic drug utilization patterns. As newer psychotropic agents are being introduced into the market, it is necessary to assess the prescribing patterns within specific local contexts, clinical factors associated with their use and their change over time. In the first psychopharmacological study of antipsychotic prescription patterns for schizophrenia in six East Asian countries and regions in 2001 (REAP-I), it was found that the second-generation antipsychotics (SGA) were generally under-utilized and Japan had a relatively higher dose and antipsychotic polypharmacy whilst China had a higher prescription of clozapine. A second study (REAP-II) was undertaken in 2004 and trends of increasing SGA use with reciprocal decreasing use of first generation antipsychotics (FGA) among the East Asian countries were noted. The current study aims to examine prescription patterns of psychotropic drugs, relevant associated factors with antipsychotic polypharmacy (defined as prescription of two or more antipsychotics) and their inter-relationships with associated phenomena such as long acting antipsychotic use, prescription of FGA and SGA medications within a tertiary psychiatric hospital setting in Singapore.We conducted a cross-sectional pharmaco-epidemiological survey of psychotropic prescription patterns for 100 hospitalized patients with schizophrenia. Data collection was performed using a standardized protocol which included patient's social and clinical characteristics, psychiatric symptoms, course of illness, and information about medications including types of drugs, dosages and adverse effects.Antipsychotic polypharmacy (74% of subjects) was associated with greater prescription of long acting antipsychotic, FGA use, higher antipsychotic dose and lower Brief Psychotic Rating Scale scores. Use of long acting antipsychotic was associated with older age group, less likelihood of SGA use, greater likelihood of antipsychotic polypharmacy, anticholinergic use and use of higher dosage of antipsychotic. Prescription of FGAs was associated with older age, verbal aggression, a higher total daily chlorpromazine equivalent dosage, higher rates of antipsychotic polypharmacy and lesser use of SGA. SGA prescription was associated with younger age, less prescriptions of anticholinergic and long acting antipsychotic medications but not antipsychotic polypharmacy.We observed significant rates of antipsychotic polypharmacy but also in the use of SGA and prescription of low antipsychotic doses. The importance having regular psychotropic prescription audits and follow up studies may allow evaluation of all patterns of antipsychotic use including polypharmacy, promote understanding of contextual prescription trends and encourage consideration of rational prescription practices including antipsychotic polypharmacy.