The Hopkins HIV Report A bimonthly newsletter for healthcare providers Volume 8, Number 4, November 1996

Are Protease Inhibitors Cost Effective?

John G. Bartlett, M.D.
and Richard D. Moore

Protease inhibitors have revolutionized therapeutic strategies in managing HIV infection. Many feel, however, that their high cost threatens to bankrupt the system. The new regimens that are now widely advocated normally cost between $9,000-12,000 per year. The potential impact of this price tag on provider organizations is awesome: the projected cost for AIDS Drug Assistance Programs (ADAP) is $436 million per year. These projections introduce the dual challenge of finding sources of funds and justifying this expense at this time of cost reduction throughout the system.

A model of cost-effectiveness that we have constructed is based on projections using available data for combination treatment with protease inhibitors compared to AZT monotherapy [Moore RD and Bartlett JG. PharmacoEconomics 1996; 10:109]. The regimen used in the model was "triple therapy" with AZT, 3TC, and indinavir. The drug costs used in the model were based on average wholesale cost plus a 20% mark-up. This resulted in a total cost of $700/month for triple therapy plus $50/month (on average) for viral load monitoring. The cost of AZT monotherapy was estimated from a prior study which examined the cost-effectiveness of AZT monotherapy compared to no therapy [Moore RD, Hidalgo J, Bareta JC, et al. J Acquir Immune Defic Syndr 1994; 7:349-54].

Costs for medical care are based on the report of Hellinger [JAMA 1993; 270:474-8], stratified by CD4 count and reported for 1992, resulting in the following costs for care, per month:

• CD4 count 200-500 cells/mm3, without AIDS: $430
  
  
• CD4 count <200 cells/mm3, without AIDS defining condition: $990
  
  
• AIDS: $1890
  
  
• AIDS, 6 months prior to death: $4000

Estimates of morbidity and mortality with AZT monotherapy are based on our experience at Hopkins as previously reported [Chaisson RE, Keruly JC, Moore, RD. N Engl J Med 1995; 333:751-6]. The benefit of therapy is estimated from the VA study using viral burden correlates with CD4 slope [O'Brien WA, Hartigan PM, Martin D, et al. N Engl J Med 1996; 334: 426-31] .

The incremental cost of triple therapy is greatest in the early stage of the disease because pharmaceutical costs exceed those for resource utilization in the care of complications. Cost benefit increases with prolonged duration of asympto-matic disease, delays in the time to AIDS, and delays in the time to death. Our model shows that if triple therapy is associated with an average 3 year extension of life, there would be an incremental cost of $30,000. This equates to a cost-effectiveness ratio of $10,000 per life-year gained. If there was no decrease in health care costs except for pharmacy costs, the in-cremental cost would be $54,000 ($750/month x 6 years) or $18,000 per life-year gained.

A critical question for health care planners concerns the merits of treatment with protease inhibitors compared to other therapeutic strategies using cost effectiveness based on cost per life-year gained. Comparisons for some treatments that have been readily accepted as medical standards are summarized in Table 1.

Table 1: Cost Effectiveness of Protease Inhibitor Regimens
Compared to Other Selected Medical Interventions

Adapted from: PharmacoEconomics 1996 Aug: 10(2): 109-113

The conclusion from this analysis is that the cost of the new regimens advocated for HIV infected persons appears to be cost effective compared to other commonly accepted strategies in medical care.

Figure 1: Model of the cumulative direct costs of medical care in patients with HIV infection receiving antiretroviral therapy. Costs are based on an analysis of the direct healthcare costs for patients with HIV infection in the U.S. [Hellinger FJ. JAMA 1993; 270: 474-8]. Reprinted, with permission, from PharmacoEconomics 1996 Aug: 10 (2): 109-113.