Two legislators are calling on the company that makes opioid overdose antidote naloxone to lower the price of the drug nationwide. Last month, the company, Amphastar Pharmaceuticals, agreed to offer a $6 rebate per dose to agencies in New York state.

“Over the past several months, police departments, law enforcement agencies, and public health officials across the country have warned about the increasing price of naloxone, which they use to combat the scourge of heroin abuse,” Senator Bernie Sanders of Vermont and Representative Elijah Cummings of Maryland wrote in a letter to Amphastar.

“Although we are encouraged by your stated willingness to work with other states, it remains unclear why your company has not already lowered its prices in states other than New York,” the lawmakers wrote. “The rapid increase in the cost of this life-saving medication in such a short time frame is a significant public health concern.”

The high cost of naloxone has prevented its widespread use, The Hill reports. In some cases, prices for the drug have increased by 50 percent or more. Naloxone reverses the effects of an overdose of heroin or opioid painkillers.

The antidote has long been used by emergency rooms and paramedics. Recently, the World Health Organization said increasing the availability of naloxone could prevent more than 20,000 deaths in the United States annually. Naloxone works quickly, without side effects.

A growing number of states have passed laws increasing access to the antidote.

In January, the Clinton Foundation announced it had negotiated a lower price for a device that delivers naloxone. The device, called Evzio, will be available at a lower price to institutions that can distribute naloxone more widely, such as police departments and universities.