Economic impact of antiretroviral therapy prescription decisions in the context of rapid scaling-up of access to treatment: lessons from Mexico Sergio Bautista-Arredondo a , Aditya Mane a,b and Stefano M. Bertozzi a,c Background: Mexico started scaling-up access to antiretroviral treatment in the late 1990s. Even though the Mexican Health System enrolled patients at impressive speed, in the initial years important aspects of the quality of care were overlooked. Objective: To describe antiretroviral prescribing and adherence practices in Mexico during initial scaling-up of antiretroviral treatment in comparison to national treatment guidelines and to estimate the associated economic cost. Methods: Eleven public sector hospitals provided detailed patient chart data. Monthly observations formed the basis of scenarios aligned by calendar month and by month before and after initiation of triple therapy. The scenarios varied by extent of prescrip- tion refill, adherence levels, and compliance with national treatment guidelines. Results: Antiretroviral therapy prescription practices were largely inconsistent with published guidelines. Non-recommended combinations were prescribed to between 54 and 79% patients-months per year. Additionally, more than 50% of patients experi- enced four to 13 changes in treatment. Modeling of the economic impact of treatment practices showed that it would have been possible to effectively treat the same number of patients at the same or lower cost per patient. Conclusions: In addition to dispensing drugs, countries scaling-up antiretroviral therapy must find ways to ensure consistent drug supply, appropriate prescription practices and effective levels of adherence. Failing to do so will seriously reduce treatment effectiveness, greatly increasing the cost per unit of health benefit. With very low levels of effective adherence patients may even be harmed and the spread of multi- drug resistant virus facilitated. ß 2006 Lippincott Williams & Wilkins AIDS 2006, 20:101–109 Keywords: economics, economic evaluation, costs, AIDS, highly active antiretroviral therapy Introduction The revolution in the care of patients with HIV/AIDS caused by the advent of antiretroviral therapy (ART) in the mid 1990s [1,2], has only recently started to reach patients in resource-constrained settings [3]. However, only 12% of the estimated 6 million people living in the developing world who need ART are receiving it [3,4]. A number of recent developments over the past 2 to 3 years have greatly improved the likelihood that ART coverage will increase significantly. These include From the a National Institute of Public Health, Cuernavaca, Mexico, the b HAAS School of Business, University of California, Berkeley, California, USA, and the c Center for Economic Research and Teaching (CIDE), Mexico City, Mexico. Correspondence to Stefano M. Bertozzi, Instituto Nacional de Salud Pu ´ blica, Av. Universidad 655, Cuernavaca, Morelos 62508, Me ´xico. E-mail: sbertozzi@correo.insp.mx Received: 12 November 2004; revised: 29 March 2005; accepted: 7 April 2005. ISSN 0269-9370 Q 2006 Lippincott Williams & Wilkins 101