World Health Organization Model List of Essential Medicines

The World Health Organization (WHO) Model List of Essential Medicines is a guideline for national governments that want to ensure they have an inventory of the medicines needed by every health system.

The list is important because:
 * it forms the basis of national drugs policy in many countries, both developed and developing (e.g. South Africa, Eritrea).
 * governments refer to WHO recommendations when making decisions on health spending.

Essential medicines: theory and practice
The original 1977 WHO definition of “essential medicines” was that they were ‘of utmost importance, basic, indispensable, and necessary for the healthcare needs of the population’. The concept was mentioned in one of the ten points of the 1978 Alma Ata Declaration on primary health care.

The difficulty of putting this into practice is reflected in the rather longer and more categorical 2002 definition:

"‘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 situations; exactly which medicines are regarded as essential remains a national responsibility.’"

The WHO Model List of Essential Medicines has been updated every two years since 1977. The current version, the 15th list, dates from March 2007.

Sections
The constituents of the list remain controversial. The list is divided into two sections:
 * Core medicines that are efficacious, safe, and cost effective medicines for priority conditions.
 * Medicines that are efficacious, safe and cost effective, but that are not necessarily affordable, or for which specialized healthcare services are required.

Cost-to-benefit ratio
Cost effectiveness is difficult to define and is the subject of fierce debate between producers (pharmaceutical companies) and purchasers of drugs (national health services).

Number of drugs
The number of drugs has nearly doubled, from 186 in 1977 to 320 in 2002. The range has increased substantially over the years and now includes antimigraine drugs, antidotes, and antineoplastic drugs.