Essential medicines are those that satisfy the priority health care needs of the population.
They are selected with due regard to disease prevalence, evidence on efficacy and safety, and comparative cost-effectiveness.
They are intended to be available in 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. These drugs are supported as safe, effective, and of high quality. Efforts are focused on their correct prescription and rational use (rational use of drugs).
The WHO Model List of Essential Medicines (WHOML) is intended to be flexible and adaptable to many different situations; the precise definition of the medicines that are regarded as essential remains a national responsibility.