The WHO Model List of Essential Drugs has been successful in establishing and promoting the concept of essential drugs. For more than twenty years, it has served as the gold standard for countries wishing to develop their own lists and has been adapted for use in more than 150 WHO Member States. From a public health perspective, priorities for the pharmaceutical system can be identified through the use of an essential drugs list. For example, national lists are often linked to national standard treatment guidelines used for training of health workers, and can serve as a guide for the procurement of needed drugs, for reimbursement purposes in health insurance schemes and for encouraging local pharmaceutical production.

The WHO Model List has been updated every two years since it was first published in 1977. The current Model List contains a little over 300 active ingredients and is divided into a main list and a complementary list. At the last meeting of the WHO Expert Committee on the Use of Essential Drugs held in November 1999, several recommendations were made concerning the process of updating both the methodology for selecting drugs for inclusion in the Model List and the List itself. These recommendations included linking the selection of drugs on the Model List to standard treatment guidelines developed by WHO. It was also agreed that decisions on selection of essential drugs should be based on properly-identified evidence. It was recommended that the Model List should prioritize those conditions and drugs for which equitable availability and affordability should be ensured before resources are spent on other treatments. A recommendation on the need for more explicit criteria was also made.

Updating and disseminating the WHO Model List of Essential Drugs

As a result of these recommendations, a draft discussion paper "Updating and disseminating the WHO Model List of Essential Drugs: the way forward" was prepared. This was the subject of discussion at an informal consultation held by WHO in March 2001. The discussion paper highlighted various perceived problems.

The range of diseases for which essential drugs are selected is not clear

Some drugs for very rare diseases are included on the Model List, while some second-line drugs for more common diseases are not. For example, should the Model List include essential drugs for cystic fibrosis?

The selection criteria are insufficiently clear

There is much confusion about the extent to which cost, cost-effectiveness and affordability criteria are being used during selection. For example, the decision not to include antiretroviral drugs (ARVs) for HIV/AIDS has provoked global discussion. The Committee had decided not to include ARVs for the treatment of HIV/AIDS because there was insufficient evidence of their long-term effectiveness in resource-poor settings. Others believed that exclusion was based on cost considerations, and have argued that inclusion of ARVs on the Model List would create the necessary pressure to bring prices down.

Selection has been based on experience rather than evidence

In the past, the Committee has taken a decision based on the material presented and on their own professional experience. However, there is no standard format application and no systematic search for and review of evidence prior to submission before the Committee in support of decisions. Furthermore, there is no external review of the Committee's draft recommendations.

There are discrepancies between the WHO Model List and WHO treatment guidelines

About 250 of the 306 active ingredients on the current Model List are also recommended in various treatment guidelines published by different WHO programmes and departments. There are a few therapeutic categories where no WHO treatment guidelines exist (e.g. cytotoxics, hormones, diagnostic agents and gastrointestinal drugs).

However, 155 drugs recommended in the total body of WHO treatment guidelines are not on the WHO Model List of 1999. If WHO recommends that national essential drugs lists should be based on national treatment choices and guidelines, the WHO Model List could be developed in a similar way.

Drugs are included for which there is no pharmacopoeial standard, or no supplier

In 1997, there were several substances on the Model List for which there was no pharmacopoeial standard. Examples are eflornithine hydrochloride, heparin sodium, methylene blue, permethrin and primaquine.¹ There are several drugs on the Model List for which there is only one supplier, or for which the supply of quality products has always been problematic. Examples of such "abandoned" essential drugs are oily chloramphenicol injection, suramin injection, ether and eflornithine.

¹ The full list quoted by WHO in 1997 was: asparaginase, dasozin mesilate, eflornithine hydrochloride, heparin calcium and heparin sodium, methylene blue, permethrin, polygeline, potassium ferric hexacyaniferrate, and primaquine.

The reasons underlying the decisions of the committee are insufficiently recorded

The reasons for the recommendations of the Committee are summarized in footnotes to the report. However, these extensive footnotes are not reproduced in WHO Drug Information or on the WHO Medicines Website (http://www.who.int/medicines), which implies that this information is only available to the public through the Technical Report Series which is published by WHO much later. In addition, notes from earlier meetings are only available through copies of old Committee reports and are in practice difficult to find. Recently, WHO has made a data base of the recorded reasons for recent Committee decisions which is available on request. However, for many earlier decisions no records are available.

The recommendations of the committee are final and not open for review

According to the rules and procedures for WHO expert committees, the report of the Committee is prepared and approved before the end of the meeting. There are no provisions for internal and external review of the report or recommendations after the meeting. The Chair of the Committee may decide to omit a statement from the report but may only change the wording on the basis of written agreement by all members. In practice, the recommendations of the Committee and the text of the report are rarely changed after the meeting and are accepted by the Director-General of WHO.

The official report of the Committee is published late

Publication of each of the last three official reports in English in the WHO Technical Report Series has taken over a year. As the Committee meets every two years, the report of the previous meeting and the new WHO Model List therefore came out just before the next meeting, which seriously undermines the usefulness of the report and even of the meeting itself. The French, Spanish and Russian translations of the 1997 report came out even later.

In recent years, this problem has partly been solved by publishing the Model List (without notes, and only in English) in WHO Drug Information and on the WHO Medicines Website.

Recommendations from the informal consultation

A series of questions was presented during the informal consultation in March 2001 and the following recommendations were issued.

1. The definition of essential drugs is still adequate and does not need to change: "Essential drugs are those drugs that satisfy the health care needs of the majority of the population. They should therefore be available at all times in adequate amounts and in appropriate dosage forms, at a price the individual and the community can afford (1)."

2. The WHO Model List should continue to be presented in two levels. The core list should indicate the minimum drug needs for a basic health care system, listing the most cost-effective drugs for priority conditions; while the complementary list should consist of drugs for priority diseases which are cost-effective but not necessarily affordable, or which may need specialized health care facilities, and should include essential drugs for less frequent diseases. The section on reserve anti-infective agents could thus be integrated into the complementary list.

3. The process of updating the Model List should be more systematic and transparent. A revised standardized format for applications should be drawn up, to include a systematic review of comparative efficacy, safety and cost-effectiveness. An external review of these draft applications and systematic reviews should be undertaken prior to submitting them to the Expert Committee.

4. The report of the Expert Committee should specify the reasons for the decision, link the drug to the relevant WHO treatment guideline and summarize the evidence. The report and the Model List should be published both electronically and in hard copy.

5. Several sections of the current Model List need to be reviewed systematically and as a whole; this process should be undertaken in close collaboration with the disease programmes concerned, drawing on the expertise of all the relevant WHO Expert Advisory Panels. Development of this process will require several meetings of the Expert Committee over the next two years.

6. An essential drugs library should be created on the WHO Website, which should include at least: summaries of WHO clinical guidelines for priority diseases; the Model List, with reasons for inclusion of drugs, and linked references to systemic reviews; WHO clinical guidelines and cost information; the WHO Model Formulary; and quality assurance information such as Basic Tests, The International Pharmacopoeia and reference standards.

7. The health care industry and patient advocacy groups could contribute to the work of the Expert Committee with relevant technical and other information as needed. Consideration should be given to the question of whether their representatives could attend the meetings of the Committee as observers.

Outline of the review process

The discussion paper with full details of the above recommendations, including the proposed procedures and information requirements, has been issued for wider consultation among WHO Member States and national essential drug programmes, United Nations agencies, the World Bank, members of WHO Expert Advisory Panels, and interested nongovernmental organizations.

All comments will be taken into consideration and the final recommendations will be reviewed by the WHO Global Cabinet later in 2001.

Reference

1. The Use of Essential Drugs. WHO Technical Report Series, No. 895 (2000).