Drug companies are working to develop a pure, more powerful version of the nation's second most-abused medicine, which has addiction experts worried that it could spur a new wave of abuse.
The new pills contain the highly addictive painkiller hydrocodone, packing up to 10 times the amount of the drug as existing medications such as Vicodin.
Four companies have begun patient-testing, and one of them -- Zogenix of San Diego -- plans to apply early next year to begin marketing its product, Zohydro.
If approved, it would mark the first time patients could legally buy pure hydrocodone. Existing products combine the drug with nonaddictive painkillers such as acetaminophen.
Critics say they are especially worried about Zohydro, a timed-release drug meant for managing moderate to severe pain, because abusers could crush it to release an intense, immediate high. Zogenix plans to file its application early next year and have Zohydro on the market by early 2013.
"I have a big concern that this could be the next OxyContin," said April Rovero, president of the National Coalition Against Prescription Drug Abuse. "We just don't need this on the market."
OxyContin, introduced in 1995 by Purdue Pharma of Stamford, Conn., was designed to manage pain with a formula that dribbled one dose of oxycodone over many hours.
Abusers quickly discovered they could defeat the timed-release feature by crushing the pills. Purdue Pharma changed the formula to make OxyContin more tamper-resistant, but addicts have moved on to generic oxycodone without the timed-release feature.
Oxycodone is now the most-abused medicine in the United States, with hydrocodone second, according to the Drug Enforcement Administration.
The latest drug tests come as more pharmaceutical companies are getting into the $10 billion-a-year legal market for powerful -- and addictive -- opiate narcotics.
"It's like the Wild West," said Peter Jackson, co-founder of Advocates for the Reform of Prescription Opioids. "The whole supply-side system is set up to perpetuate this massive unloading of opioid narcotics on the American public."
The pharmaceutical firms say the new hydrocodone drugs give doctors another tool to try on patients in legitimate pain.
The companies say a pure hydrocodone pill would avoid liver problems linked to high doses of acetaminophen, an ingredient in products like Vicodin. They also say patients will be more closely supervised because, by law, they will have to return to their doctors each time they need more pills. Prescriptions for the weaker, hydrocodone-acetaminophen products now on the market can be refilled up to five times.
Purdue Pharma and Cephalon, a Frazer, Pa.-based unit of Teva Pharmaceuticals in Israel, are conducting late-stage trials of their own hydrocodone drugs, according to documents filed with federal regulators. In May, Purdue Pharma received a patent applying extended-release technology to hydrocodone. Neither company would comment on its plans.
Meanwhile, Egalet has finished preliminary stages of testing aimed at determining the basic safety of a drug. The firm could have a product on the market as early as 2015 but wants to see how the other companies fare with the FDA before deciding whether to move forward, Lindhardt said.
Critics say they are troubled because of the dark side that has accompanied the boom in sales of narcotic painkillers: Murders, pharmacy robberies and millions of dollars lost by hospitals that must treat overdose victims.
Thousands of legitimate pain patients are becoming addicted to powerful prescription painkillers, they say, in addition to the thousands more who abuse the drugs.
Prescription painkillers led to the deaths of almost 15,000 people in 2008, more than triple the 4,000 deaths in 1999, the Centers for Disease Control and Prevention reported.
Emergency room visits related to hydrocodone abuse have jumped from 19,221 in 2000 to 86,258 in 2009, according to data compiled by the DEA.
Opiates like hydrocodone block pain but also unleash intense feelings of well-being and can create physical dependence. The withdrawal symptoms are also intense, with users complaining of cramps, diarrhea, muddled thinking, nausea and vomiting.
After a while, opiates stop working, forcing users to take stronger doses or to try slightly different chemicals.
"You've got a person on your product for life, and a doctor's got a patient who's never going to miss an appointment, because if they did and they didn't get their prescription, they would feel very sick," said Andrew Kolodny, president of Physicians for Responsible Opioid Prescribing. "It's a terrific business model, and that's what these companies want to get in on."
Under pressure from the government, Purdue Pharma last year debuted a new OxyContin pill formula that "squishes" instead of crumbling when someone tries to crush it.
But Zogenix, whose drug is time-released but crushable, says there is not enough evidence to show that such tamper-resistant reformulations thwart abuse.
At a conference for investors New York on Nov. 29, Zogenix chief executive Roger Hawley said the FDA was not pressuring Zogenix to put an abuse deterrent in Zohydro.
"We would certainly consider later launching an abuse-deterrent form, but right now we believe the priority of safer hydrocodone -- that is, without acetaminophen -- is a key priority for the FDA," Hawley said.
FDA spokeswoman Erica Jefferson said the agency would not comment on its discussions with drug companies, citing the need to protect trade secrets.