Addicts often seek Suboxone for its ability to eliminate withdrawal sickness that accompanies opiate use, Logan and others said. But without those painful physical consequences, addicts are less motivated to stop using those drugs while on Suboxone.

The goal is to minimize relapses, building addicts' confidence in their potential to quit illegal drugs. If it takes months or even years of Suboxone treatment, that's acceptable, some advocates say.

"The longer they're on it," Sharfstein said, "the better."

But critics say such treatment merely substitutes one narcotic for another. In Baltimore, recovery centers that emphasize a drug-free approach are balking at a state proposal to require them to accept patients using Suboxone or methadone - or risk losing state funding.

"Individuals can lead useful lives without the need of a mood-altering drug," an official of Gaudenzia Inc., one of Maryland's largest residential treatment programs, told state lawmakers this year.

Some recovering addicts also worry about becoming hooked on buprenorphine.

Valarie Clark has been taking Suboxone for a year under the supervision of Merrick's Total Health Care center. She calls it a "wonder drug" for having helped her kick a heroin-snorting habit of two decades.

Clark, 52, began using heroin in her 30s. Her drug use spiraled after her daughter died while having a baby in 1994. She unsuccessfully tried methadone treatment, saying it didn't stop her heroin cravings the way Suboxone does. She learned about Suboxone's effects after buying it on the street.

Now her goal is to stop taking Suboxone by February. The doctor she sees at the clinic has tapered her dose from 8 milligrams a day to 4 milligrams. Having twice used heroin while in treatment, Clark is wary of relapsing, especially since she has landed a job.

"I'm an addict, I have to be careful of all drugs, even Suboxone," she said. "At this point, I feel that it's becoming an abuse for me."

Many doctors said patients can quickly relapse when they stop Suboxone. That in turn brings on mild withdrawal and cravings for opiates. That's why doctors try to lower the daily dose over several months.

But getting patients off Suboxone's lowest dose of 2 milligrams is challenging. Some experts say it's a psychological barrier, others say it's physical.

"The biggest problem is how do we get you off [the drug] - I think it's a very real problem," said Dr. Sharon Levy, medical director of the Adolescent Substance Abuse Program at Children's Hospital in Boston and a Harvard University pediatrics professor. The program prescribes Suboxone to teenage addicts.

Yet Levy said any worries about dependence are offset by the progress that patients experience by not using heroin. "I'm struggling to get them off," she said, "but they've had two years of being off of drugs and graduating high school."

The same clinic trying to help Clark stop taking Suboxone also has patients like Lorraine Keating, who wants to remain on the drug for the foreseeable future, because she's "nervous" about falling back into heroin use.

"My life has really changed dramatically," said Keating, 55, of West Baltimore. She had been arrested numerous times for drug-related charges before starting the 24-milligram dose of Suboxone that she has been on since Jan. 23. She hasn't been arrested since beginning treatment at Total Health Care.

Helping patients with varying drug habits, such as Clark and Keating, can challenge even experienced doctors. But Congress required only an eight-hour training course covering how the drug works, addiction issues and counseling methods. Lawmakers did not want to meddle in the practice of medicine, and heeded the advice of federal health officials eager to make it easy for physicians to qualify to prescribe Suboxone.

Dr. Daniel R. Howard, who runs a private family practice in Baltimore, said he found the eight hours of training "helpful," but he wanted additional assistance and sought a mentor.

"I felt like I needed a little more guidance in dosing," said Howard, who has treated about 120 patients with Suboxone.

Dr. Karl Spector of Bel Air, an internist, has treated nearly 400 patients with Suboxone since February 2003. He said the training is "not enough" and determined that the manufacturer's guidelines for doses and duration don't meet everyone's needs. "I find that patients can determine what is the right dose for themselves," he said.