The WHO Model List of Essential Medicines, 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 medicine. As of 2016, more than 155 countries have created national lists of essential medicines based on the World Health Organizations model list. 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. The first list was published in 1977 and included 212 medications. The WHO updates the list every two years. The 14th list was published in 2005 and contained 306 medications. A separate list for children up to 12 years of age, known as the WHO Model List of Essential Medicines for Children, was created in 2007 and is in its 5th edition. (Full list...)