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The WHO Model List of Essential Medicines (aka Essential Medicines List or EML), published by the World Health Organization (WHO), contains the medications considered to be most effective and safe to meet the most important needs in a health system. The list is frequently used by countries to help develop their own local lists of essential medicines. As of 2016[update], more than 155 countries have created national lists of essential medicines based on the World Health Organization's model list. This includes both developed and developing countries.
The list is divided into core items and complementary items. The core items are deemed to be the most cost-effective options for key health problems and are usable with little additional health care resources. The complementary items either require additional infrastructure such as specially trained health care providers or diagnostic equipment or have a lower cost–benefit ratio. About 25% of items are in the complementary list. Some medications are listed as both core and complementary. While most medications on the list are available as generic products, being under patent does not preclude inclusion.
The first list was published in 1977 and included 208 medications. The WHO updates the list every two years. There are 306 medications in the 14th list in 2005, 410 in the 19th list in 2015, 433 in the 20th list in 2017, 460 in the 21st list in 2019, and 479 in the 22nd list in 2021. Various national lists contain between 334 and 580 medications.
A separate list for children up to 12 years of age, known as the WHO Model List of Essential Medicines for Children (EMLc), was created in 2007 and is in its 8th edition. It was created to make sure that the needs of children were systematically considered such as availability of proper formulations. Everything in the children's list is also included in the main list. The list and notes are based on the 19th to 22nd edition of the main list. An α indicates a medicine is on the complementary list. Therapeutic alternatives with similar clinical performance are listed for some medicines and they may be considered for national essential medicines lists.