The WHO Model Lists of Essential Medicines has been updated every two years since 1977. The current versions are the 19th WHO Essential Medicines 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, and/or specialist medical care, and/or specialist training are needed. In case of doubt medicines may also be listed as complementary on the basis of consistent higher costs or less attractive cost‐ effectiveness in a variety of settings.