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Essential medicines, as defined by the World Health Organization (WHO), are the medicines that "satisfy the priority health care needs of the population".^[1] Essential medicines are the medications that people should have access to at all times in sufficient amounts. These medications should be generally affordable.^[2] Since 1977, the WHO has published a model list of essential medicines, with the current (2019) list for adult patients containing over 400 medicines.^[3] Since 2007, a separate list of medicines intended for child patients has been published.^[4] Both the WHO adult and children's lists contain a notation indicating that a particular medication is "complementary", thus essentially there are two lists, the "core list" and the "complementary list". The core list presents a list of minimum medicine needs for a basic health care system, listing the most efficacious, safe and cost-effective medicines for priority conditions. Priority conditions are selected on the basis of current and estimated future public health relevance, and potential for safe and cost-effective treatment. The complementary list presents essential medicines for priority diseases, for which specialized diagnostic or monitoring facilities are needed. In case of doubt, medicines may also be listed as complementary on the basis of higher costs or less attractive cost-effectiveness in a variety of settings. The list is important because it forms the basis of national drugs policy in more than 155 countries, both in the developed and developing world. Many governments refer to WHO recommendations when making decisions on health spending. Countries are encouraged to prepare their own lists taking into consideration local priorities. Over 150 countries have published an official essential medicines list.^[5]

The definition of essential medicines has changed over time.

The original WHO definition in 1977 was that they were medicines "of utmost importance, basic, indispensable, and necessary for the healthcare needs of the population".^[6] The concept was mentioned in one of the ten points of the 1978 Alma Ata Declaration on primary health care.

In 2002 definition was changed to:

Essential medicines are those that satisfy the priority health care needs of the population.^[7]

And this remains the definition as of 2019.^[1]

Items are chosen as essential medicines based on how common the disease that is being treated, evidence of benefit, the degree of side effects and the cost compared to other options.^[8] In order to explore the human rights law and WHO's essential medicines policies into national legislation regarding medicines affordability and financing needs to be understood to enhance universal access to essential medicines.^[9] Perehudoff K (2020-11-02), "Universal access to essential medicines as part of the right to health: a cross-national comparison of national laws, medicines policies, and health system indicators.", Global Health Action, 13 (1699342), doi:10.1080/16549716.2019.1699342, PMC 7605313, PMID 33131456

Cost effectiveness is the subject of debate between producers (pharmaceutical companies) and purchasers of drugs (national health services). It is estimated that access to essential medicines could save 10 million people a year.^[10] Access to essential medicine is a cornerstone of effective healthcare systems and a fundamental component of global health initiatives aimed at improving quality of life reducing health disparities, and fostering sustainable development.^[11] Proper access to essential medicine can lower the amount for really expensive treatments and hospitalizations by managing early and effectively.

The WHO made the Model List of Essential Medicines in 1977 as a way to introduce the idea that there are certain medicines that are more useful and required more often than other medicines, and that these medicines are often inaccessible to many different populations.^[12]

The WHO Model List of Essential Medicines has been updated every two years since 1977. The 23rd version was published in July 2023.^[13] Over that period, the number of medications has more than doubled, from the original 208 in 1977,^[5] to more than 500 in 2023.^[13]

The first edition of the "WHO Model List of Essential Medicines for Children", was published in 2007, while the 9th edition was published in 2023.^[5][4][13] It was created to make sure that the needs of children were systematically considered such as availability of proper formulations.^[5] The first edition contained 450 formulations of 200 different medications^[5] and the 2023 list contains 361 medications.^[13]

While the WHO Essential Medicine Lists are a very valuable tool and integral to the country's medicine policy, there has not yet been enough effort to implement them. There are several factors that affect the adaptation and implementation of the WHO Essential Medicine Lists, as found by a 2022 qualitative evidence synthesis.^[14] This study identified areas that need support in order to implement EML at a country level. ^[14]

Implementation of the WHO EML can be done with national medication selection committees that are able to operate with consultive mandates.^[14] These committees also need very clear leadership, monitoring, and evaluations. Implementation of EMLs can be done efficiently if there is a form of a reimbursement process, and recommended clinical practices that help to translate the EML to a clinical setting easily.^[14] Finally, there also needs to be clear legislation and monitoring to make sure there is compliance.^[14]

Access to essential medicines are part of the Sustainable Development Goals, specifically goal 3.8.^[15]

A number of organizations, which are global in scope, use the list to determine which medications they will supply.^[5] Rather than strictly following the list, many nations refer to the essential medicines list as a guide for developing their own laws and regulations based on their own requirements.^[16]

• Campaign for Access to Essential Medicines
• Universities Allied for Essential Medicines
• Department of Essential Drugs and Medicines
• List of World Health Organization Essential Medicines