Trends in Carbapenem Antibiotics Utilization, Costs, and Market Dynamics in Medicaid: A Retrospective Analysis from 1991 to 2023

Marwan A Alrasheed¹Abdulrahman A Alsuhibani^2*

• ¹Department of Clinical Pharmacy, College of Pharmacy, King Saud University, Riyadh, Saudi Arabia
• ²1. Department of Pharmacy Practice, College of Pharmacy, Qassim University,, Qassim 51452,, Saudi Arabia

Carbapenems are critical antibiotics used to treat severe infections, especially those caused by multidrug-resistant organisms. Understanding their utilization, reimbursement, and pricing trends is vital to inform healthcare policies and ensure sustainable access. This study analyzed longitudinal trends in carbapenem use, market dynamics, and economic impact within Medicaid from 1991 to 2023. A retrospective analysis was conducted using publicly available Medicaid State Drug Utilization data. Four carbapenems—imipenem/cilastatin, meropenem, ertapenem, and doripenem—were examined. Data on prescriptions, reimbursements, and proxy pricing (reimbursement per prescription) were extracted and analyzed. Trends and market shares were evaluated annually using descriptive statistics and visualized with Excel and Power BI. Joinpoint regression identified significant directional shifts over time. Carbapenem utilization and reimbursement grew markedly between 2015 and 2020, reflecting increased reliance on these agents for severe infections. Imipenem/cilastatin peaked in 2005 at 22,883 prescriptions (APC: 12.28%; 95% CI: 11.33–14.03; p < 0.001), with reimbursements of $7.6 million. A sharp decline followed (APC: -30.36%; 95% CI: -33.96 to -25.44; p < 0.001), with reimbursements falling to $839,581 by 2023. Meropenem prescriptions peaked at 53,355 in 2016 (AAPC: 17.29%; 95% CI: 13.97–29.71; p < 0.001), with reimbursements stabilizing at $7.2 million in 2023. Ertapenem, introduced in 2002, showed the greatest growth, peaking in 2021 with 116,988 prescriptions and $30.7 million in reimbursements (APC: 19.05%; 95% CI: 13.56–109.30; p = 0.023). Doripenem peaked at 2,954 prescriptions in 2011 but declined rapidly (APC: -39.24%; 95% CI: -52.08 to -35.15; p < 0.001), with reimbursements nearing zero by 2017. Post-2021 declines across all agents may reflect stewardship efforts and a shift toward narrower-spectrum therapies. This study underscores evolving carbapenem utilization patterns, shaped by clinical practices, stewardship programs, and policy changes. Ongoing surveillance is essential to balance effective infection management with antimicrobial resistance containment and cost control. Further research should explore the long-term effects of stewardship and new therapeutic options on carbapenem use.