To contain a surge in opioid drug-related deaths in the United States, state and local governments are pouring money into programs to make an overdose antidote more widely available even as prices rise - creating a growth opportunity for manufacturers.

Naloxone, approved by regulators decades ago, has gone up tenfold in price in recent years, making the drug more lucrative. That's led police, emergency responders, and schools to seek government subsidies to acquire the medication.

At least two companies are awaiting approval to enter the market this year with nasal-spray versions, competing with four that already make an injectable drug. A kit to turn one of the most popular versions of the antidote into a nasal spray currently costs about $45 a dose, including $30 for the medicine.

About 16,000 Americans die each year after taking too many opioid painkillers, such as OxyContin or Opana, and an additional 8,000 died in 2013 after overdosing on heroin, another opioid - a fivefold increase from 2001. That has led to a national campaign by advocates of addiction treatment to make naloxone more widely available as an emergency aid.

The White House has proposed $12 million in the 2016 budget for state grants to fight opioid overdose-related deaths, including money to buy naloxone and train emergency responders on how to use it. Some states have passed laws to make it easier for private citizens to get naloxone, such as family members of addicts. And manufacturers, envisioning a market in which every household keeps an emergency supply of the drug, are advocating for even wider distribution.

"We believe that there is a huge potential if doctors who prescribe pain medication were to write companion scripts for intranasal naloxone," Jason Shandell, president of Amphastar Pharmaceuticals Inc., said in an email. "Although it may never be used, people should keep intranasal naloxone in their medicine cabinet just in case a family member or friend experiences an overdose due to pain medication, etc."

Naloxone kits were distributed to almost 100,000 drug users, friends, or family from 2010 to June 2014, compared with just over 50,000 in the decade and a half before, according to the Centers for Disease Control and Prevention. This resulted in 26,463 overdose reversals between 1996 and June 2014. Local overdose prevention programs in the U.S. provide naloxone kits to private citizens at 600 sites nationwide, as at least 30 states and the District of Columbia have passed laws to increase access to the antidote.

Amphastar has been one of the biggest beneficiaries of the surge in demand for naloxone. For police departments and addiction treatment groups, the company's injectable version of the drug is the right concentration for retrofitting with an attachable atomizer to create a nasal spray. Naloxone helped boost Amphastar's revenue from fully manufactured drugs by 41 percent in the second quarter from a year earlier to $30.6 million, excluding a blood-clot medication whose sales the company discloses separately.

A dose of injectable naloxone costs about $30 - up about 1,000 percent from 15 years ago - according to Daniel Raymond, policy director for the advocacy group Harm Reduction Coalition.

Prices have skyrocketed in part because a field with fewer competitors has reduced pressure on companies to keep prices down. The drug has been made at one time or another by as many as a dozen companies since Endo International P.LC. received FDA approval for the brand-name version, Narcan, in 1971.

Endo is headquartered in Dublin, Ireland, but executives work from Malvern.