Rationalising Antipsychotic Polypharmacy: A Cross-sectional, Pre- and Post-intervention Comparative Study

Background: Antipsychotic polypharmacy, the coprescribing of 2 or more antipsychotics, carries risk but has a valid place in treating schizophrenia. Monotherapy is usually preferred according to best practice guidelines. Lack of documented prescribing reasons limits assessment of guideline adherence and therefore polypharmacy rationalisation. A pragmatic pharmacist-led intervention was implemented to address issues, including suboptimal documentation, contributing to non-guideline-adherent antipsychotic polypharmacy prescribing. Objective: To evaluate the impact of the intervention through a pre- versus post-intervention comparison of antipsychotic polypharmacy prevalence and prescribing burden, rate of documentation of prescribing reasons, and degree of guideline adherence. Methods: A retrospective, cross-sectional medical record audit was conducted to quantify polypharmacy prevalence, and the burden of its prescribing in terms of defined daily doses (DDDs) and maximum licensed daily doses (MLDDs). Documented prescribing reasons were noted and assessed against accepted practice guidelines. Findings were compared against those reported at baseline. Results: Post-intervention antipsychotic polypharmacy prevalence was 39.1% (vs 39.0% at baseline; P = 1.00). In the post-intervention polypharmacy cohort, mean combined DDD ± SD was 2.63 ± 1.16 (vs 2.84 ± 1.11 at baseline; P = 0.447) and mean combined MLDD ± SD was 136% ± 56% (vs 131% ± 39% at baseline; P = 0.675). Prescribing reasons were documented in 68.0% of audited polypharmacy cases (vs 36.7% at baseline; P = 0.012); 58.8% of documented reasons were guideline-adherent (vs 54.5% at baseline; P = 1.00). Conclusion and relevance: The intervention was not associated with changes in antipsychotic polypharmacy prevalence, magnitude nor degree of guideline adherence, but significantly improved rates of documentation. Compared with baseline, where prescribing reasons were largely unclear, the improved post-intervention documentation supported prescribers to make informed decisions about polypharmacy rationalisation. This research has reinforced the important role that pharmacists play in bridging communication gaps contributing to non-guideline-adherent polypharmacy.