Chlamydia prescribing trends in Australia before and after a national guideline update: a retrospective study of sentinel surveillance data, 2015–2025

Background This study investigated prescribing practices following changes in the Australian chlamydia treatment guidelines in 2022, which replaced doxycycline or azithromycin with doxycycline as first-line therapy for oropharyngeal or urogenital infections. Methods Data from 61 clinics in the Australian Collaboration for Coordinated Enhanced Sentinel Surveillance of STIs and blood-borne viruses (ACCESS) project (January 2015–June 2025) from individuals aged 16–80 years with positive urogenital or pharyngeal chlamydia tests were analysed. An interrupted time series analysis (intervention point Q1 2022) assessed quarterly changes in the proportion of tests prescribed doxycycline and azithromycin within 14 days before and 31 days after positive tests. Anorectal infections were excluded as doxycycline was already the first line recommendation for this anatomical site. Results A total of 69,925 positive tests (53,202 (76.1%) at sexual health clinics (SHCs)) from 60,084 people were included. Doxycycline prescribing increased by 1.61 percentage points (95% CI, 1.47–1.75) per quarter before the guideline change; immediately increased by 13.5 percentage points (95% CI, 8.58–18.4); then increased by 1.70 percentage points (95% CI, 1.08–2.31) post-change. The proportion treated with azithromycin decreased by 0.62 percentage points (95% CI, −0.79 to −0.44) per quarter pre-guideline change; immediately decreased at the change by 18.1 percentage points (95% CI, −22.75 to −13.52); then decreased 1.64 percentage points (95% CI, −2.09 to −1.19) post-change. SHCs and general practices specialising in the care of gay and bisexual men showed greater pre-change increases in doxycycline prescribing, whereas general practice and community health accelerated post-change. Conclusions Doxycycline prescribing for chlamydia has increased with corresponding declines in azithromycin use following the 2022 Australian treatment guideline change. Setting-specific implementation strategies may accelerate evidence uptake for future guideline updates.