(Bloomberg) -- The Food and Drug Administration approved Emergent BioSolutions Inc.’s Narcan, an emergency opioid overdose reversal treatment, for over-the-counter use on Wednesday. It’s the first opioid antidote to be available without a prescription, which will ease access for thousands of patients and their families. Here’s what you need to know about it:

Does Narcan work on heroin and fentanyl overdoses?

Narcan nasal spray is a lifesaving treatment for people who overdose on opioids, including fentanyl and heroin. 

How does it work? 

When a person is experiencing an opioid overdose, breathing slows and the brain is starved of oxygen. This can lead to cardiac arrest, brain damage and death. Narcan is an opioid antagonist that kickstarts respiratory function, saving lives. 

Using Narcan in an individual experiencing an overdose may result in severe opioid withdrawal characterized by an elevated heart rate, nausea and nervousness, according to the FDA. Experts say its critical to call emergency responders when administering Narcan.

Read More: An Opioid Overdose Kit Lets Anyone Respond to an Emergency

Who manufactures it? 

Emergent, a company better known for developing and manufacturing countermeasures for biological threats like anthrax and smallpox.

How much will it cost? 

A spokesperson for Emergent said Wednesday there’s “nothing new to share on price at the moment.” Advocates are concerned about how Emergent will price its over-the-counter product, worried it will be inaccessible without insurance co-pays. The FDA acknowledges that the price will be set by the manufacturer. 

“We encourage the manufacturer to make accessibility to the product a priority by making it available as soon as possible and at an affordable price,” said FDA Commissioner Robert Califf in a news release. 

When and where will it be available? 

Over-the-counter Narcan will be available in stores late summer, an Emergent spokesperson said. The company hasn’t shared which stores will carry the spray, but the FDA statement says the goal is for it to be available through multiple channels, like drug stores and convenience stores.

--With assistance from Jeannie Baumann.

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