Essential medicines: purpose, criteria, history, access and global challenges

What defines an essential medicine

Medicines are selected for the list on the basis of public health relevance, evidence of efficacy and safety, and comparative cost‑effectiveness. The aim is not to list every medicine but to prioritize those that address the most important needs of a society and health system. This concept helps ensure a core set of products is available to treat common conditions and emergencies, thereby covering the "basic needs" of health care providers and patients (basic needs).

Scope and composition

The list includes small‑molecule drugs, medicines for chronic diseases, emergency treatments, and vaccines. Over time the list has grown to include a large number of medicines and immunizations; by the mid‑2010s the model list described more than three hundred individual medicines and vaccines (drugs and vaccines included). A substantial majority of items on the list are off‑patent, which makes it easier for generic manufacturers to supply them at lower cost.

History and review process

The WHO model list was first published in 1977 and is updated regularly by an expert committee. Reviews are scheduled every two years to consider new evidence, new treatments, and changing disease burdens. Many countries have used the WHO list as a foundation for national essential medicines lists and procurement policies; the process has been widely adopted in low‑ and middle‑income settings (developing countries).

Uses and importance

• Guiding national procurement and budgeting for public health programs.
• Supporting clinical treatment guidelines and formularies used in hospitals and clinics.
• Helping insurance schemes and reimbursement systems decide which medicines to cover.
• Encouraging manufacturers and suppliers to prioritize affordable, high‑impact products.

Access gaps and controversies

Despite its aims, the essential medicines concept faces persistent challenges. Market failures occur for diseases that primarily affect poorer regions, which can reduce incentives to develop new treatments for illnesses such as malaria and tuberculosis. Conversely, some newer or high‑cost medicines — including many antiretroviral drugs for HIV/AIDS and certain cancer therapies — may be effective but unaffordable for public systems. Studies have documented large gaps in availability and affordability; a World Bank analysis and other assessments have estimated that a substantial fraction of the global population still lacks reliable access to all essential medicines.

Notable distinctions and adaptations

Countries typically adapt the WHO model list to local needs, producing national lists that reflect local disease burdens, budgets and supply capabilities. Separate editions exist for adults and for children, and over time the list has incorporated newer classes of medicines while balancing clinical benefit with affordability. The model list remains an influential policy tool: it shapes procurement, informs clinical practice, and highlights where international action is needed to improve equitable access to safe, effective and affordable medicines.