Chris Hawley, AP

It is the nation's second-most abused medicine, linked to murders, celebrity overdoses and a rising tide of violent pharmacy robberies. However, since 1999 federal regulators have put off deciding whether to tighten controls over hydrocodone, the addictive narcotic that is the key ingredient in Vicodin and other medicines.

The Drug Enforcement Administration and Food and Drug Administration insist they are still actively studying whether to move hydrocodone-containing medicines from the Schedule III category of medicines to the more restrictive Schedule II. The 12-year delay is frustrating drug treatment counselors, lawmakers and relatives of overdose victims. "They're not doing a darn thing," said Robert DuPont, president of the Institute for Behavior and Health, a Rockville, Maryland-based think tank. "There's no study that takes 12 years. When you think how many people have died of hydrocodone overdoses, it's inexcusable."

Nationally, emergency room visits related to non-medical hydrocodone use have quadrupled since 2000 — from 19,221 to 86,258 in 2009. In Florida alone, hydrocodone caused 910 deaths and contributed to 1,803 others between 2003 and 2007. Actors Heath Ledger, Brittany Murphy and Corey Haim all died from drug cocktails containing it. A DEA review of police drug labs shows seizures of hydrocodone-containing pills number second only to those of oxycodone, the narcotic used in drugs like OxyContin and Percocet. Hydrocodone seizures have soared from 13,659 in 2001 to 44,815 in 2010.

In March, alarmed by the rising rates of abuse, 58 members of Congress filed a bill that would bypass the DEA and FDA's rulemaking process and tighten controls on hydrocodone. "The FDA is about controlling dangerous drugs, and they're just not doing their job here," said Rep. Mary Bono Mack, R-California, one of the bill's sponsors. Legitimate pain patients, meanwhile, are worried that such a move could jack up their medical expenses by forcing them to repeatedly return to their doctors for refills. They also worry doctors will be afraid to prescribe needed medicines for fear of attracting FDA scrutiny.

Hydrocodone is a painkiller that is chemically similar and almost as strong as oxycodone, the active ingredient in the drug OxyContin. Pills that combine oxycodone with another painkiller like acetaminophen or aspirin are strictly controlled as Schedule II drugs. The category includes products like Percocet and Percodan, but their hydrocodone equivalents like Vicodin, Norco and Lortab, fall under the less-restrictive Schedule III.

The legal difference dates from 1970, when hydrocodone was mainly used as a cough suppressant instead of a painkiller and scientists knew less about how narcotics work on the human body. The classification has led to dramatic differences in the way the drugs are regulated. Schedule II drugs must be kept under lock and key at pharmacies, doctors can only prescribe one bottle at a time, and patients must have an original prescription slip with them. State punishments for abusers are severe, and traffickers can face up to 20 years in prison for the first offense under federal law.

In contrast, prescriptions for Schedule III medications can be refilled up to six times without a doctor visit, and doctors can renew prescriptions by phone or fax. Additionally, the penalties for abusing Schedule III drugs are lighter - a maximum 10 years for first-time traffickers under federal law. States have their own drug schedules for punishing abusers and lower-level drug dealers, but they usually mirror the federal categories.

Drug treatment clinics have been warning about the dangers of easier access to hydrocodone since the early 1990s, and in 1999 the DEA agreed to review whether combination products containing it should be rescheduled. Twelve years later, the DEA and FDA say they are still in the preliminary stages of that review.

The boom was underscored in June, when a man walked into a pharmacy on New York's Long Island and gunned down four people before leaving with 11,000 hydrocodone pills. Hydrocodone pills on the market today each contain no more than 10 mg of the drug, while some kinds of oxycodone pills contain up to 80 mg. But the lower content doesn't stop abusers. "It doesn't make any difference — people will just take more of them," said Ronald Dougherty, the former director of the Pelion, Inc. drug treatment center in Syracuse, New York.

Dougherty filed the original petition in 1999 requesting that hydrocodone combination products be changed to Schedule II. About 80 percent of patients to his clinic were on hydrocodone, and many had gotten addicted after being prescribed the drug for legitimate injuries or surgery, he said. Since then the study has been repeatedly passed back and forth between the two agencies, documents show. Abbott Laboratories, which makes Vicodin, and Watson Pharmaceuticals, which makes Norco, said neither of the agencies has turned to them for input.

Meanwhile, new experiments show hydrocodone is more seductive to the brain than once thought. In two studies sponsored in 2008 and 2009 by the National Institutes of Health, volunteers were given roughly equal doses of pure hydrocodone and oxycodone. Scientists then tested the volunteers to measure their intoxication and hunger for more of the drug. The results were nearly identical, researchers said. "The Schedule III designation of these hydrocodone products does not necessarily indicate lower abuse potential," researchers wrote.

Legitimate patients fear that rescheduling hydrocodone will make it harder for them to get much-needed pain relief. Pattie Crossen, who has fibromyalgia and degenerative spinal disc disease, has to drive 65 miles and pay a $40 co-payment every time she visits a pain specialist to renew her hydrocodone prescription. "It's going to be another med that I have to travel 130 miles to get," said Crossen, 55. "It's just a big, huge added expense."

Requiring more doctor visits could increase costs for insurance companies and Medicare, said Jessica Waltman, vice president of government affairs for the National Association of Health Underwriters, which represents health insurance brokers. But in the long term there might be savings because there would be fewer addicts in rehab programs and emergency rooms, she said. "I would think there would be some cost savings if you are preventing people from abusing drugs," Waltman said.