To assess the impact of the COVID-19 pandemic on prescription drug use and costs.

Interrupted time series analysis of comprehensive administrative health data linkages in British Columbia, Canada, from 1 January 2018 to 28 March 2021.

Retrospective population-based analysis of all prescription drugs dispensed in community pharmacies and outpatient hospital pharmacies and irrespective of the drug insurance payer.

Between 4.30 and 4.37 million individuals (52% women) actively registered with the publicly funded medical services plan.

COVID-19 pandemic and associated mitigation measures.

Weekly dispensing rates and costs, both overall and stratified by therapeutic groups and pharmacological subgroups, before and after the declaration of the public health emergency related to the COVID-19 pandemic. Relative changes in post-COVID-19 outcomes were expressed as ratios of observed to expected rates.

After the onset of the pandemic and subsequent COVID-19 mitigation measures, overall medication dispensing rates dropped by 2.4% (p

The COVID-19 pandemic impact on prescription drug dispensing was heterogeneous across medication subgroups. As data become available, dispensing trends in nervous system agents, antibiotics and antivirals warrant further monitoring and investigation.