Objective To investigate the association of antipsychotic
polypharmacy in schizophrenia with cost of primary and
secondary health service use.
Method Comparative analysis of health service cost for
patients prescribed antipsychotic polypharmacy versus
antipsychotic monotherapy. Resource utilisation and costs
were described using central Danish registers for a 2 year
period (2007–2008). We included patients attached to one
of two Danish psychiatric referral centres in 1 January
2008 and/or 1 January 2009. Their prescribed treatment
with either antipsychotic polypharmacy or monotherapy at
the two cross-sectional dates was recorded and used as
proxy of polypharmacy exposure during the preceding
year. A multivariate generalised linear model was fitted
with total costs of primary and secondary health service use
as dependent variable, and antipsychotic polypharmacy,
diagnosis, age, gender, disease duration, psychiatric inpatient
admissions, and treatment site as covariates.
Results The sample consisted of 736 outpatients with a
diagnosis in the schizophrenia spectrum. Antipsychotic
polypharmacy was associated with significantly higher
total health service costs compared with monotherapy
(2007: 25% higher costs; 2008: 17% higher costs) when
adjusting for potential confounders and risk factors. A
subgroup analysis suggested that the excessive costs
associated with antipsychotic polypharmacy were partly
accounted for by the functional level of the patients.
Conclusion The results demonstrate that antipsychotic
co-prescribing is associated with increased use of health
care services, even though no causal relations can be
inferred from an observational study.