Narcan, a prescription nasal spray that reverses opioid overdoses, can now be sold over the counter, the Food and Drug Administration said on Wednesday, authorizing a move long-sought by public health officials and treatment experts, who hope wider availability of the medicine will reduce the nation’s alarmingly high drug fatality rates.

By late summer, over-the-counter Narcan is expected to be for sale in big-box chains, supermarkets, convenience stores, gas stations and online retailers. New York City plans to install Narcan vending machines later this year.

The commissioner of the F.D.A., Dr. Robert M. Califf, said in a statement that the over-the-counter authorization was meant to address a “dire public health need.”

“Today’s approval of O.T.C. naloxone nasal spray will help improve access to naloxone, increase the number of locations where it’s available and help reduce opioid overdose deaths throughout the country,” Dr. Califf said. “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.”