Every two years, the World Health Organization (WHO) releases a medication list that it believes should be available, if needed, to all the people of the Earth. The latest iteration of the essential medicines list has just been released. It’s a compendium like the ones health insurers maintain to help them determine which medicines should be covered by their policies. Think of it like The Worlds Formulary.

That may sound dull or at least rather wonky. But there are real-world implications when a drug makes — or is not approved for — this list. The move to include HIV drugs in 2002 arguably helped to make lifesaving antiretrovirals available to AIDS patients in developing countries. More recently, the addition hepatitis C drugs to the list appears to have put them on a similar trajectory.

The list is meant to help countries figure out how to prioritize spending on medications. It’s a model that many use to craft their own drug formularies — while individual countries may make tweaks here and there, they don’t each need to set about inventing this wheel.

For the first couple of decades, the list was drawn up based on expert advice. But that and other things changed shortly after the turn of the century. Since that time, the selection process has used an evidence-based approach. The committee drawn together to update the list reviews the studies that have been conducted that either support a recommendation to include a drug or to delete it from the list.

There have been other changes, too. Before 2001, a drug had to be needed by a majority of the population to be included on the list, which meant medicines for uncommon diseases didn’t make the cut. But that criterion was dropped and the list now includes medications like factor VIII, a clotting protein for hemophiliacs, and surfactant, which opens up the lungs of premature babies.

A drug’s cost was a deciding factor prior to 2001 with the idea being that a medication’s price should be low and affordable. But that’s a difficult bar to set when you’re looking at the whole world, he noted.

Now decisions are based on a drug’s usefulness, its safety and effectiveness, and the quality of the evidence supporting it. Smart idea!