Modeling the impacts of restrictive formularies on patients with HIV

To model the impacts of restrictive formulary designs on outcomes for patients with HIV and to demonstrate the costs of restricting access to novel HIV regimens with better safety and efficacy profiles.

We modified an epidemiological model of HIV incidence, progression, and treatment to simulate the effects of 5 formulary scenarios on patient outcomes in the United States.

Using a cohort of HIV-susceptible individuals, we followed patients through HIV infection, disease progression, and death. Patients transitioned in and out of treatment states once infected. Treatment discontinuation, efficacy, and the rate of adverse events (AEs; renal failure and bone fracture) in each formulary scenario depended on the treatment path and regimens included. Outcomes of interest included all-cause cumulative deaths, annual rates of AEs, and costs associated with treating those AEs.

All outcomes of interest were more favorable in less restrictive formulary scenarios that provided fewer barriers to appropriate treatments. By 2025, more restrictive formularies would have resulted in 171,500 more cumulative bone and renal events among treated patients with HIV compared with an open formulary. This corresponds to AE treatment costs of $3.65 billion in more restrictive formularies compared with $1.43 billion in an open formulary. Finally, compared with an open formulary, there would be an additional 16,200 cumulative deaths in more restrictive formularies.

Less restrictive formulary designs, which allow patients with HIV to initiate potentially safer and more efficacious regimens based on their proclivity to AEs, yield better outcomes and reduce costs.