No health system in the world offers unlimited access to all medicines. Rational selection of essential medicines is one of the core principles of a national drug policy. It focuses therapeutic decisions, professional training, public information, financing, supply and quality assurance efforts on those medicines which will have the greatest impact in a given health care setting. It is a global concept which can be applied in any country, in both public and private sectors and at different levels of the health care system. Rational selection and use can be pursued through various tools.

National treatment guidelines are defined by WHO as systematically developed evidence-based statements which assist providers, patients and other stakeholders to make informed decisions about appropriate health interventions. Guidelines have mostly been used to advise practitioners on which interventions to use in their interactions with patients.

National lists of essential medicines should be developed for different levels of care and on the basis of standard treatment guidelines for common diseases and conditions that should be treated at each level. Careful selection of essential medicines is the first step in ensuring access.

Rational use of essential medicines is one of the core activities of health workers and patients. Trained and motivated health staff, and the necessary diagnostic equipment, are needed to ensure safe and effective treatments, minimizing the risks and waste linked to irrational prescribing and use of medicines.