management. Resolution number 28.66 at the Assembly requested the WHO Director-General to implement the proposal, which led subsequently to an initial model list of essential drugs (WHO Technical Series no 615, 1977). This model list has undergone regular review at approximately two-yearly intervals and the current 14th list was published in March 2005. The model list is perceived by the WHO to be an indication of a common core of medicines to cover most common needs. There is a strong emphasis on the need for national policy decisions and local ownership and implementation. In addition, a number of guiding principles for essential drug programs have emerged. The initial essential drugs list should be seen as a starting point. Generic names should be used where possible, with a cross-index to proprietary names. Concise and accurate drug information should accompany the list. Quality, including drug content stability and bioavailability, should be regularly assessed for essential drug supplies. Decisions should be made about the level of expertise required for drugs. Some countries make all the drugs on the list available to teaching hospitals and have smaller lists for district hospitals and a very short list for health centers. Success depends on the efficient supply, storage and distribution at every point. Research is sometimes required to settle the choice of a particular product in the local situation. The model list of essential drugs The model list of essential drugs is divided into 27 main sections, which are listed in English in alphabetical order. Recommendations are for drugs and presentations. For example, paracetamol appears as tablets in strengths of 100 mg to 500 mg, suppositories 100 mg and syrup 125 mg/5ml. Certain drugs are marked with an asterisk (previously a ៛), which denotes an example of a therapeutic group, and other drugs in the same group could serve as alternatives. The lists are drawn up by consensus and generally are sensible choices. There are ongoing initiatives to define the evidence that supports the list. This demonstrates the areas where RCTs (randomized controlled trials) or systematic reviews exist and serves to highlight areas either where further research is needed or where similar drugs may exist which have better supporting evidence. In addition to work to strengthen the evidence base, there is a proposal to encourage the development of Cochrane reviews for drugs that do not have systematic review evidence. Application of NNTs (numbers needed to treat)