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In a bid to battle antibiotic resistance, the World Health Organization for the first time has classified antibiotics into three categories, including one that lists the drugs it hopes will not be used except in circumstances of dire need.

The antibiotic breakdown is part of the WHO’s essential medicines list, which is updated every two years. The 2017 iteration was published Tuesday.

The section on antibiotics divides these critical drugs into three categories. Those that should be go-to drugs for common infections are listed as “access” antibiotics. Others for which growing resistance is a problem are listed under the category “watch” to signal they should not be first or second options.


The final category is “reserve” — a name that signals that these are drugs that should only be used to treat infections for which other options have failed.

“These medicines should be protected and prioritized as key targets in [antibiotic] stewardship programs to preserve their effectiveness,” Dr. Marie-Paule Kieny, the WHO’s assistant director-general for health systems and innovation, said during a news conference.


Kieny said the hope is that the list will help health systems and doctors use antibiotics in a way that will better preserve their usefulness. For instance, the drug ciprofloxacin shouldn’t be prescribed for urinary tract or upper respiratory tract infections — even though it often is.

“We don’t see this as a quick fix solution,” Kieny said of the ranking tool. “But we know that where preservation of antibiotics has worked, through hospital stewardship programs, we have seen a reduction in resistance trends.”

Outside experts hailed the decision to rank antibiotics in this way.

“The updated essential medicines list should help ensure antibiotics of last resort are reserved only for when first-line treatments will not work and that doctors in all countries have easy access to the best and most appropriate treatments,” Dr. Tim Jinks, head of the Wellcome Trust’s drug resistant infection program, said in a statement.

Among the drugs in the reserve category is colistin, an old antibiotic that has been a drug of last resort. Concern about its continued usefulness has arisen, however, because of the emergence of a superbug called mcr-1 — a gene that allows bacteria to withstand the drug.

Dr. Suzanne Hill, WHO’s director of essential medicines and health products, said having a list of antibiotics the world shouldn’t use unless absolutely necessary will require a rethinking of the way manufacturers are compensated for making drugs in that class.

“We don’t want colistin used very frequently. In fact, we don’t want it used at all,” she said.

Pharmaceutical companies normally recoup their development costs through sales but in the case of these drugs, the goal is to restrict sales to the greatest degree possible. Other forms of compensation — ways to reward companies for not promoting use — might include cash awards or buying out licenses, Hill said.