(2002; 28 pages) [French] [Spanish]
The concept of essential medicines
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. Careful selection of a limited range of essential medicines results in a higher quality of care, better management of medicines (including improved quality of prescribed medicines), and more cost-effective use of health resources.
The WHO Model List of Essential Medicines
Most countries require that a pharmaceutical product be approved on the basis of efficacy, safety and quality before it can be prescribed. In addition, the majority of health care and insurance schemes cover only the costs of medicines on a selected list. The medicines on such lists are selected after a study of the medicines used to treat particular conditions, and a comparison of the value they give in relation to their cost. The WHO Model List of Essential Medicines (the “Model List”) is an example of such a list. The Model List has been updated every two years since 1977.
The Model List and its procedures are meant as a guide for the development of national and institutional essential medicine lists. It was not designed as a global standard. However, over the past 25 years the Model List has led to a global acceptance of the concept of essential medicines as a powerful means to promote health equity. By the end of 1999, 156 Member States had official essential medicines lists, of which 127 had been updated in the previous five years. Most countries have national lists and some have provincial or state lists as well. National lists of essential medicines usually relate closely to national guidelines for clinical health care practice which are used for the training and supervision of health workers. Lists of essential medicines also guide the procurement and supply of medicines in the public sector, schemes that reimburse medicine costs, medicine donations, and local medicine production. Many International organizations, including UNICEF and UNHCR, as well as nongovernmental organizations and international non-profit supply agencies, have adopted the essential medicines concept and base their medicine supply system mainly on the Model List.
As a model product, the WHO Model List aims to identify cost-effective medicines for priority conditions, together with the reasons for their inclusion, linked to evidence-based clinical guidelines and with special emphasis on public health aspects and considerations of value for money. The information available in the Essential Medicines Library (see below) is specifically aimed to assist national and institutional committees in developing national and institutional lists of essential medicines.
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 which are efficacious, safe and cost-effective but not necessarily affordable, or for which specialised health care facilities or services may be needed.
The square box symbol indicates that a listed medicine should be seen as a representative example from a group of clinically equivalent medicines with wide experience of use, within a pharmacological class. The medicine listed on the Model List would generally be the least costly therapeutic equivalent within the group. National lists should not use a similar symbol and should be specific in their final selection, which would depend on local availability and price.
The procedures for updating the Model List are in line with the WHO recommended process for developing clinical practice guidelines1. Key components are a systematic approach to collecting and reviewing evidence and a transparent development process with several rounds of external review. This process is intended as a model for developing or updating national and institutional clinical guidelines and lists of essential medicines. Detailed information on the process, the information included in the application and the review process are available from the WHO/medicines website (www.who.int/medicines).
1 Development of WHO Practice Guidelines: Recommended Process. Geneva: WHO. 2001 Document WHO/EIP (October 2001)
The choice of essential medicines depends on several factors, including the public health relevance and sound and adequate data on the efficacy, safety and comparative cost-effectiveness of available treatments. Stability in various conditions, the need for special diagnostic or treatment facilities and pharmacokinetic properties are also considered if appropriate. When adequate scientific evidence is not available on current treatment of a priority disease, the Expert Committee may either defer the issue until more evidence becomes available, or choose to make recommendations based on expert opinion and experience.
Most essential medicines should be formulated as single compounds. Fixed-ratio combination products are selected only when the combination has a proven advantage in therapeutic effect, safety or compliance over single compounds administered separately.
In cost comparisons between medicines, the cost of the total treatment, and not only the unit cost of the medicine, is considered. Cost and cost-effectiveness comparisons may be made among alternative treatments within the same therapeutic group, but will generally not be made across therapeutic categories (for example, between treatment of tuberculosis and treatment of malaria). The absolute cost of the treatment will not constitute a reason to exclude a medicine from the Model List that otherwise meets the stated selection criteria. The patent status of a medicine is not considered in selecting medicines for the Model List.
In adapting the WHO Model List to national needs, countries often consider factors such as local demography and pattern of diseases; treatment facilities; training and experience of the available personnel: local availability of individual pharmaceutical products; financial resources; and environmental factors.
The WHO Essential Medicines Library
In addition to the information on whether a medicine is in the Model List or not, it is important for national or institutional selection committees to have access to information that supports the selection of essential medicines, such as summaries of relevant WHO clinical guidelines, the most important systematic reviews, important references and indicative cost information. Other information is also linked to the medicines in the Model List, such as the WHO Model Formulary and information on nomenclature and quality-assurance standards. All this information is presented on the WHO web site as the “WHO Essential Medicines Library” (www.who.int/medicines) intended to facilitate the work of national committees. The library is under construction and will be further expanded over time.
Quality of products
Priority should be given to ensuring that available medicines have been made according to good manufacturing practices and are of assured quality. Factors that will need to be considered are:
• knowledge of, and confidence in, the origin of the product;
• the pharmaceutical stability of the product, particularly in the environment that it will be used;
• where relevant, bioavailability and bioequivalence information
It is recommended that medicines be purchased from known manufacturers, their duly accredited agents, or recognised international agencies known to apply high standards in selecting their suppliers.