Drug Saf. 2025 Nov 4. doi: 10.1007/s40264-025-01633-7. Online ahead of print.
ABSTRACT
BACKGROUND: Medicine shortages are an increasing threat to medicine safety and access. In Australia, a 7-month shortage of Coumadin 5-mg tablets (Dec 2022-Jul 2023) prompted Therapeutic Goods Administration (TGA) intervention via the Serious Scarcity Substitution Instrument (SSSI), allowing pharmacists to substitute 5-mg warfarin tablets with lower-strength tablets. Understanding the impact of this shortage on anticoagulant use and safety is essential for informing future regulatory responses.
AIMS: The aim of this study was to assess the impact of the 2023 warfarin shortage in Australia on dispensing of warfarin and direct oral anticoagulants (DOACs), International Normalised Ratio (INR) testing, and adverse event reporting.
METHODS: Monthly national dispensing data (January 2020-August 2024) were obtained from Pharmaceutical Benefits Scheme (PBS) Date of Supply data. INR pathology data were sourced from Services Australia. The TGA Medicines Shortages Database identified relevant shortage periods. Warfarin-related adverse events were extracted from the TGA Database of Adverse Event Notifications. Interrupted time series assessed changes in dispensing and INR testing trends over time.
RESULTS: Warfarin dispensing declined by 1094 prescriptions per month prior to March 2023 (p < 0.0001). A short-term increase occurred in March 2023 (+ 8625 prescriptions; p = 0.0017) following implementation of the SSSI, although this was not sustained. At the warfarin strength level, dispensing rose for warfarin 1 mg and 2 mg but fell for 5 mg, with subsequent compensatory increases; 3 mg remained stable. DOAC dispensing increased steadily before March 2023 (+ 3771 prescriptions per month; p < 0.0001) but declined thereafter (- 3056 per month; p < 0.0001), most notably for rivaroxaban and dabigatran, while apixaban decreased non-significantly. INR testing briefly increased during the shortage and SSSI. A modest rise in haemorrhage-related adverse events was observed.
CONCLUSION: Warfarin supply was maintained during the 2023 shortage through strength-based substitution under the SSSI, with limited impact on DOAC dispensing.
PMID:41186801 | DOI:10.1007/s40264-025-01633-7
