(A-142) Prescribing Patterns, Polypharmacy, and Drug-Drug Interactions among People Living with HIV in Australia: Insights using National Medication Dispensing Data

Background: Over 38 million people worldwide, including 28,000 in Australia, live with HIV, with many relying on ART to manage their condition. While simplified ART regimens have improved adherence, aging PLWH in Australia still face challenges with polypharmacy and DDIs due to rising comorbidities, with prevalence estimates varying widely and lacking population-level data.

Objectives: This study aims to assess the prevalence of polypharmacy and DDIs among Australian PLWH and examine trends in ART treatment and comorbidities, particularly post-COVID-19. It hypothesises that while ART access and comorbidities remained stable, polypharmacy and DDI rates may have risen, especially among older PLWH.

Methods: A retrospective cohort study analysed a 10% random PBS sample, examining ART and concomitant medications from January 2019 to March 2024. ART prevalence and incidence rates were calculated, with the most dispensed concomitant medications ranked and classified by comorbidities using the Rx-Risk Comorbidity Index. Polypharmacy and DDI trends were assessed over time, highlighting common DDIs.

Results: The study identified 2,610 individuals with HIV (mean age: 55.6 years, SD: 12.8, 87% male) and 678 individuals with polypharmacy (62.1, 11.1, 88% respectively). The prevalence of ART drug classes declined slightly overall from pre- to post-pandemic, however, the decline were minor and not significant due to consistent prescribing proportions. While incidence rates fluctuated during the same period, they remained overall stable. These shifts likely reflect changes in treatment guidelines and preferences rather than pandemic-related effects. Among the overall and polypharmacy cohorts, the most prescribed drug classes were alimentary tract & metabolism (22%, 25%) and anti-infectives for systemic use (23%, 16%). Common comorbidities included hyperlipidaemia, pain, depression, gastro esophageal reflux disease, chronic heart failure, and diabetes, with chronic airway disease becoming more prevalent post-pandemic. Polypharmacy affected 26% of PLWH, peaking in 2022 and declining thereafter, with higher rates among older individuals (77% for 50+, 23% for 18–49). Clinically significant DDIs were prevalent in 52% of PLWH including red (10%) and amber (42%). Red and amber DDI rates rose significantly (353% and 109%, respectively) but stabilised after 2022. PIs (darunavir) and PEs (cobicistat), accounted for most clinically significant DDIs (red: 8/10; amber: 5/10).

Conclusions: The pandemic minimally affected ART prescribing and comorbidities but increased respiratory diseases. Polypharmacy and DDIs rose before declining post-2022, likely due to updated guidelines. PIs and PEs remain key contributors, highlighting the need for prescriber interventions.