The U.S. government told doctors this week to consider prescribing medications that reverse overdoses to many more patients who take opioid painkillers, a move that could add more than $1 billion in health care costs.

Assistant Secretary for Health Brett Giroir, a doctor appointed by President Donald Trump, announced the guidance on Wednesday, saying it's important for doctors to discuss overdose dangers with patients.

Prescribing the overdose medication naloxone, which is sold under the brand names Narcan and Ezvio, along with opioids forces a conversation that will lead to "a more informed decision by the patient," he said.

The action comes a day after a close vote from a Food and Drug Administration expert panel endorsing the idea of rewriting opioid drug labels to include a naloxone recommendation for many or all patients. An FDA document said such a move could add more than $1 billion in health care costs.

"Even at a billion, it would be an investment that is well worth it," Giroir said.

More than 47,600 Americans died of opioid overdoses last year, a toll that has been rising for two decades. The street drug fentanyl is the top killer today, but prescription painkillers are still a problem, contributing to nearly 15,000 overdose deaths last year.

Naloxone comes in a nasal spray, an injection and an automatic injector. The Narcan nasal spray costs about $125 for a two-dose kit, although government programs can get it for less. The automatic injector can cost as much as $4,000 per kit, although its maker recently authorized a cheaper generic version.

Critics said prescribing the antidote to pain patients does not address the growing share of fatal overdoses caused by illicit opioids, and could cause shortages for programs that hand out the kits to drug users on the street.

It "will have the unintended consequence of derailing efforts to provide naloxone to the very effective community programs we know are successful in saving lives," said Dr. Raeford E. Brown Jr., who heads an expert panel advising the FDA.

The new guidance tells doctors to consider prescribing the antidote to patients on high doses of opioids, heavy drinkers, people with sleep apnea and other breathing problems, people taking benzodiazepines such as Xanax and people with addiction or mental health problems.

It expands upon a similar recommendation from the Centers for Disease Control and Prevention.

In April, U.S. Surgeon General Jerome Adams issued the office's first national public health advisory in 13 years, calling on more Americans to start carrying naloxone and urging more federal money to be dedicated to broadening access.

Most states allow people to get naloxone from a pharmacy or community program under a statewide prescription and some states require doctors to also prescribe naloxone to patients on high doses of opioids.

The FDA is working toward an over-the-counter version of naloxone.

Brown said the government should use its emergency authority to buy and distribute large quantities of naloxone and immediately make it available over the counter. Trump directed the health agency to declare the opioid crisis a public health emergency last year.

"That's the difference between declaring a public health emergency and actually acting as if there's a public health emergency," Brown said.