CROI 2023: CAB/RPV-LA levels are not reduced after switching from efavirenz
10 March 2023. Related: Conference reports, PK and drug interactions, CROI 30 (Retrovirus) 2023.
Because efavirenz (EFV) induces UGT1A1/CYP3A4 and this might lead to early clearance of CAB/RPV-LA, researchers modelled this potential interaction using an in-house PKPB model. Results presented at CROI 2023 suggests that this is not a concern. 
A cohort of 100 people was modelled to simulate the impact of EFV on CAB/RPV levels. All predicted values were within a 2-fold range of clinical data. Initiation of LA-CAB/RPV 12 hours after the final EFV dose only had a small effect on Cmin values.
CAB and RPV Cmin were ≥87% of the expected value. This effect was transient and Cmin at day-28 was 98% of control.
Bettonte S. Intramuscular cabotegravir/rilpivirine concentrations after switching from efavirenz. 30th Conference on Retroviruses and Opportunistic Infections, 19 – 22 February 2023, Seattle and hybrid. Poster Abstract 508.