For personal use. Only reproduce with permission from The Lancet Publishing Group. REVIEW In 1977, the birth of the WHO model list of essential drugs led the organisation to advocate for the principle that some medicines were more essential than others, pointing out that many medicines in developing countries were not useful, whereas others that were did not reach populations at need. In the past 25 years, 11 revisions of the list have been published and 156 WHO member states have adopted medicines lists. 1 The list has been much debated: the pharmaceutical industry has attacked it for being too restrictive, and non-governmental organisations (NGOs) have been critical, in particular of the scant attention paid to AIDS. Selection criteria for drugs have evolved, including a change from an experience-based to an evidence-based approach. The name has also changed, from essential drugs lists (EDL) to essential medicines lists (EML). In 1977, essential medicines were “of utmost importance, basic, indispensable and necessary for the health and needs of the population” 2 and criteria relating to safety, quality, efficacy, and total cost were defined. 2 By 2002 the following definition was proposed: “Essential medicines are those that satisfy the priority health care needs of the population. They are selected with due regard to public health relevance, evidence on efficacy and safety, and comparative cost- effectiveness. Essential medicines are intended to be available within the context of functioning health systems at all times in adequate amounts, in the appropriate dosage forms, with assured quality and adequate information, and at a price the individual and the community can afford. The implementation of the concept of essential medicines is intended to be flexible and adaptable to many different Lancet 2003; 361: 1723–29 Boston University School of Public Health, Boston, MA, USA (R Laing MD); Massachusetts College of Pharmacy and Health Sciences, Boston, MA (B Waning MPH); Department of Experimental and Clinical Pharmacology, Nelson R Mandela School of Medicine, University of Natal, Congella, South Africa (A Gray MScPharm); Médecins Sans Frontières, London, UK (N Ford BSc); and Médecins Sans Frontières, Paris, France (E ‘t Hoen LLM) Correspondence to: Dr Richard Laing, Boston University School of Public Health, 715 Albany St, T4W, Boston, MA 02118, USA (e-mail: richardl@bu.edu) situations; exactly which medicines are regarded as essential remains a national responsibility.” 3 In this paper, we review the list’s history, evolution, application by countries, controversies, and future challenges. 4 History The 1975 World Health Assembly 5 asked WHO to assist member states in selecting and procuring essential medicines, assuring good quality and reasonable cost (panel 1). 2,4,5–18 The first list of 205 items (186 medicines) was published 2 years later. 2 At the 1978 Alma Ata conference, provision of essential medicines was identified as one of eight key components of primary health care. 6 The 1985 Nairobi conference resulted in the development of WHO’s revised drug strategy, in which the model list was recognised as important mainly for public sectors; the emphasis was moved beyond selection of drugs to their procurement, distribution, rational use, and quality assurance. 9 In 1991, membership of the WHO Expert Committee on the Use of Essential Drugs was balanced by including “professionals in essential drugs programmes in developing countries” 4 and by providing comparative cost information. 4 During this period, many countries and NGOs adopted the essential medicines approach, 10 and the UN emergency health kit included 55 of the list medicines. When the 1999 expert committee met to revise the model list, they expressed concern at the lack of evidence provided to justify revisions and asked that “a summary of the appropriate evidence be presented for review”. 12 Around this time, the effect of the World Trade Organization (WTO) trade-related aspects of intellectual property rights (TRIPS) agreement on access to medicines was being debated by NGOs, the pharmaceutical industry, and governments. 13 In a WHO discussion document 25 years of the WHO essential medicines lists: progress and challenges Richard Laing, Brenda Waning, Andy Gray, Nathan Ford, Ellen ‘t Hoen Review THE LANCET • Vol 361 • May 17, 2003 • www.thelancet.com 1723 The first WHO essential drugs list, published in 1977, was described as a peaceful revolution in international public health. The list helped to establish the principle that some medicines were more useful than others and that essential medicines were often inaccessible to many populations. Since then, the essential medicines list (EML) has increased in size; defining an essential medicine has moved from an experience to an evidence-based process, including criteria such as public- health relevance, efficacy, safety, and cost-effectiveness. High priced medicines such as antiretrovirals are now included. Differences exist between the WHO model EML and national EMLs since countries face varying challenges relating to costs, drug effectiveness, morbidity patterns, and rationality of prescribing. Ensuring equitable access to and rational use of essential medicines has been promoted through WHO’s revised drug strategy. This approach has required an engagement by WHO on issues such as the effect of international trade agreements on access to essential medicines and research and development to ensure availability of new essential medicines. Search strategy We did comprehensive literature searches using Medline and EMBASE. Emphasis was placed on articles published from 1975–2002 containing information on the implementation, use, effect, and relevance of essential drug lists in developing countries.