Krystal began using heroin (search) when she was 14 years old, and it didn't take long for her to become hooked. The teen dropped out of school, lost a ton of weight and hocked her belongings to support a $200 a day habit.

Now 18, Krystal said she is drug-free, holds down a job, attends beauty school and cares for her toddler son. She credits a relatively new medication called buprenorphine (search) with plucking her from heroin's grasp.

"Amazing," "incredible" and "lifesaving" are a few of the words addicts use to describe buprenorphine, which blocks heroin cravings. The problem is that relatively few can get it, and health professionals are pressuring the government to expand access.

Available in this country since late 2002, buprenorphine is an alternative to methadone (search), long the primary treatment for heroin addiction. It is also used to treat addictions to prescription painkillers like OxyContin (search), Percocet (search) and Vicodin (search).

Doctors say buprenorphine has many advantages over methadone, including that it is longer acting, more difficult to overdose on and easier to withdraw from.

"It has been extraordinarily effective in the patients we have given it to," said psychiatrist Herbert Kleber of Columbia University, who started one of the first buprenorphine programs in the nation.

Addicts, meanwhile, say "bupe" gives them a feeling of clearheadedness they don't get with methadone. They can be treated in the privacy of their doctor's office, enabling them to avoid the stigma associated with public methadone clinics.

But federal law limits individual doctors and medical practices to prescribing buprenorphine to 30 patients at a time, making the drug very hard to get in areas where heroin and prescription opiate abuse is high. For example, Krystal's doctor, J. Charles Lentini, says he has a waiting list of 185 addicts — many of whom are continuing to abuse drugs while they wait.

Even more problematic is the restriction on large medical practices, which means that a health plan like Kaiser Permanente, the nation's largest not-for-profit health maintenance organization with 8.2 million members, can treat just a few hundred addicts at any one time nationwide.

Bills pending in the House and Senate would eliminate the 30-patient restriction for group medical practices while retaining it for individual doctors. The Senate passed similar legislation last year, but it died in the House.

"It clearly was not our intention" that addicts have less access to buprenorphine because they happen to go to a group practice, said Sen. Carl Levin, D-Mich., co-author of the Drug Addiction Treatment Act of 2000 (search). The law paved the way for doctors to prescribe buprenorphine but also established the 30-patient limit. Levin introduced the bill now pending.

Meanwhile, the U.S. Substance Abuse and Mental Health Services Administration (search) said it is working on a regulatory fix to expand access to buprenorphine.

"The group practice issue we see very much as a critical barrier," said Robert Lubran, the agency's director of pharmacologic therapies.

Krystal said she spent eight agonizing months on Lentini's waiting list before finally getting her buprenorphine prescription last month. She entered detox two or three times while she waited, but returned to heroin each time she was discharged.

"It was torture," said Krystal, whose boyfriend is on the waiting list. "I just wanted to feel normal again."

Another of Lentini's patients, David, took heroin for six years and has been on buprenorphine for 13 months. The 43-year-old day trader said he "thanks God" that he got the drug when he did. David, who spent time in prison for accidentally killing a woman with his car while high, was among Lentini's first patients when he got out.

"If there was a waiting list, I'd be in jail now, because my urine would be hot," he said.

Both Krystal and David spoke on the condition that their last names not be used.

The 30-patient limit is not the only barrier to access.

Less than 1 percent of the nation's doctors — 4,850 out of 600,000 — have received federal Drug Enforcement Administration certification to prescribe buprenorphine, which comes in a pill and is sold under the brand names Suboxone (search) and Subutex (search).

The number of doctors actually prescribing the drug might be even smaller. Kleber said the manufacturer, Reckitt Benckiser, told him last year that only 1,500 had written a buprenorphine prescription. Reckitt Benckiser officials did not return a phone call.

Many doctors shy away from treating heroin addicts because they believe those patients will be disruptive, Kleber and other experts said.

"Most practicing physicians carry the baggage that much of society carries around the treatment of addictive disorders," said Dr. David Fiellin, chairman of the buprenorphine department at the American Society of Addiction Medicine.

Also, buprenorphine is expensive, typically costing around $300 to $350 a month, and is not always covered by private insurance or by Medicare or Medicaid.