Relationship between adherence to antiretroviral therapy and the cost-effectiveness of antiretroviral therapy and the patterns of antiretroviral regimen switches

The rapid growth in the number of drugs approved to treat Human Immunodeficiency Virus (HIV) infection has transformed the management of HIV disease. The death rate from HIV-disease has continued to fall since the Food and Drug Administration approval of the newer antiretroviral drugs. Antiretroviral therapy consists of medication regimens with significant side effects, toxicities, and drug interactions. Adherence to antiretroviral therapies presents special issues that result from the biology of HIV, the magnitude of the required therapeutic effect, and the changing demography of HIV infection. Nonadherent behavior has promoted drug resistance and cross-resistance among drugs in a therapeutic class limiting future treatment options. Recent data suggest that viii the level of medication adherence required for optimal treatment effectiveness is extremely high and that adherence levels exceeding 95 percent are required for optimal viral suppression. The high costs of these drugs, as well as the increased life expectancy of patients with HIV are driving up the overall health care costs associated with HIV infection. Few studies have modeled the pharmacoeconomic impact of nonadherence of therapies in persons with HIV. The objectives of the research study were to assess the relationship between patient adherence to antiretroviral therapy and: (1) cost-effectiveness of antiretroviral regimens; and (2) patterns of antiretroviral regimen switches. Markov Monte Carlo simulations were conducted to determine the costs and effects of adherence behavior. The results of the study indicate that the mean overall annual HIV-related medical costs were $22,751. Overall, probabilistic sensitivity analyses indicate that adherent behavior, compared to non-adherent behavior, is associated with an incremental cost-effectiveness ratio below $15,000/QALY. In addition, the results of this study indicate that there are more treatment switches in non-adherent individuals compared to adherent individuals as the enrollment period increases. For clinicians and healthcare policy makers, it is important to take into account the impact of adherence behavior on disease progression and the costeffectiveness of interventions. Future health economic studies to assess the ix potential impact of adherence interventions in HIV-infected patients receiving care in the VA setting are needed and the role of pharmacists in managing adherence behavior should be explored.