Pharmaceutical policy and off-label prescribing in pregnancy: A population-based historical cohort study analyzing inequality in access to antiemetics within Australia's Pharmaceutical Benefits Scheme

Abstract

Introduction

Nausea and vomiting in pregnancy is highly prevalent and can significantly impact pregnant women's quality of life. Despite this, access to effective pharmacotherapies can be constrained by stringent regulatory controls and socioeconomic barriers. The objective of this study was to examine the socioeconomic distribution of antiemetics (metoclopramide, ondansetron, and prochlorperazine) dispensed to pregnant women through Australia's publicly subsidized Pharmaceutical Benefits Scheme.

Material and Methods

We used the Maternity1000 linked administrative dataset to characterize antiemetics dispensed during 297 630 pregnancies in Queensland, Australia (July 2013 to June 2018). Using a population-based historical cohort study design, we analyzed dispensing volume, prevalence, and government expenditure across socioeconomic quintiles, with socioeconomic disadvantage defined using the Australian Bureau of Statistics' Index of Relative Socioeconomic Disadvantage. Inequalities in medication access and public expenditure were assessed using concentration indices (C) and concentration curves.

Results

Off-label ondansetron dispensings for nausea and vomiting in pregnancy (i.e., use outside Therapeutic Goods Administration-approved indications and not subsidized under the Pharmaceutical Benefits Scheme) accounted for the largest share of public expenditure (53.5%), followed by metoclopramide (45.2%) and prochlorperazine (1.3%). Across all three antiemetics, prevalence was highest among women in the most socioeconomically disadvantaged quintiles and declined progressively across the two least disadvantaged groups. Small pro-poor inequalities in access (C < −0.10) and moderate pro-poor inequalities in public expenditure (C > −0.25) were observed across all antiemetics. (Medication access: C_{metoclopramide} = −0.07, 95% CI (−0.080 to −0.068); C_ondansetron = −0.09, 95% CI (−0.114 to −0.075); C_{prochlorperazine} = −0.08, 95% CI (−0.109 to −0.045). Government expenditure: C_{metoclopramide} = −0.30, 95% CI (−0.316 to −0.285); C_ondansetron = −0.25, 95% CI (−0.297 to −0.198); C_{prochlorperazine} = −0.28, 95% CI (−0.350 to −0.205)).

Conclusions

Off-label ondansetron access accounted for the majority of public expenditure on antiemetics dispensed during pregnancy, revealing a disconnect between health policy, clinical practice, public expenditure, and pregnant women's needs. While pro-poor access and public subsidies for antiemetics align with the equity elements embedded in the design of the Pharmaceutical Benefits Scheme, they may also be reflective of inequitable access to other unsubsidized, guideline-recommended pharmacotherapies for nausea and vomiting in pregnancy.