After coming under fire from angry lawmakers in the wake of its recent decision to more than double the price of its opioid intervention drug naloxone, Amphastar says that the FDA has handed it a rejection for an intranasal version of the treatment.

The Rancho Cucamonga, California based biotech company did not spell out all the reasons for the rejection or go into much detail in its statement, but the company cited the agency’s questions about a “user human factors study, device evaluation, and other items.”

CRLs, though, aren’t public, so there’s no way to check on exactly what regulators are objecting to.

Naloxone is a medication used to block the effects of opioids, especially in overdose. When given intravenously, it works within two minutes, and when injected into a muscle, it works within five minutes. The medication may also be used in the nose. The effects of naloxone last about half an hour to an hour

Naloxone was patented in 1961 and approved for opioid overdose by the Food and Drug Administration in 1971. It is on the World Health Organization’s List of Essential Medicines, the most effective and safe medicines needed in a health system. Naloxone is available as a generic medication.

A pair of US senators, Susan Collins and Claire McCaskill, on the Special Committee on Aging, took Amphastar, Pfizer, Mylan, Adapt Pharma and Kaleo to task last summer for hiking the price of naloxone as opioid abuse ran rampant in the country.

Amphastar raised its price of naloxone in early 2015 from $19 a dose to $41 and lawmakers have criticized the players in the field for a ten-fold increase in recent years, right alongside a national opioid addiction crisis.

Amphastar’s CEO, Dr. Jack Zhang, stated: “While we are disappointed to have not received approval at this time, we intend to continue to work with the FDA to address their concerns in the CRL and hope to bring Intranasal Naloxone to the market as soon as possible.”

Amphastar already sells naloxone in pre-filled syringes, as does privately held Kaleo Pharmaceuticals, which came under fire earlier this year for raising the price of its naloxone device Evzio by 550 percent to $4,500.

Adapt Pharma Ltd already has two naloxone nasal spray formulations approved by the U.S. FDA.