Severe cramping and shaking, three weeks of vomiting — for addicts looking to kick the habit, enduring the body's painful response to withdrawal can be a major obstacle to getting clean.

But imagine a treatment that could painlessly wean you off of drugs in a few hours. It's called rapid detox (search), a controversial and expensive treatment that has advocates claiming a miracle cure for patients who have become addicted to painkillers, and critics concerned about the promises of a pricey quick-fix that might not hold over time.

For Larry Loyd, a California animal lover, four surgeries for a neurological disorder had left him with a 10-year addiction to painkillers. He took 40 Norcos (search) — the equivalent of 80 Vicodin (search) — a day, and could barely function or take care of his dozen pets.

"It's not a craving, you don't take it because you want to get high or anything like that," Loyd said. "No, when you're addicted, your body, you're physically addicted," he said.

Like many addicts, Loyd tried traditional rehab programs, but couldn't handle the weeks-long detox process. The violent shaking, cramping and vomiting would drive him back to the pills.

So, Loyd gathered $15,000 to pay for rapid detox, a procedure that condenses the withdrawal process into about two hours while the addict is asleep. FOX News followed Loyd while he underwent the treatment.

Loyd's rapid detox treatment was performed by Dr. Clifford Bernstein, M.D., medical director of the Waismann Institute, the nation's leading rapid detox center. Dr. Bernstein explained how drugs plug into the body's nerve receptors, short-circuiting the body's pleasure-pain system.

Drugs shut down pain and turn up pleasure. When those drugs are suddenly withheld from the body, the addict experiences tremendous pain.

For rapid detox, Loyd was hospitalized, placed under anesthesia in intensive care. His body was flooded with a cocktail of medicines that stripped the drugs away from the nerves. He was also given a massive infusion of a drug that blocked his brain cells' need for opiates. Were the patient awake for the procedure, the treatment would be extremely painful.

"We're pushing all of the opiate medication off of his brain, off of the receptors on the brain and replacing it with the naltrexone (search), the blocking agent," Dr. Bernstein explained as Larry underwent the treatment. "So right now, Larry is going through a withdrawal," he said.

"At about one year, our success rate is anywhere between 65 and 75 percent," Dr. Bernstein said.

Critics, however, say those numbers are not substantiated with follow-up drug testing, and are very worried about the procedure's safety and cost.

"Even if it were safe — and I think the evidence is still out on that — even if it were as effective as they claimed, it still would be extraordinarily expensive for what you're getting," said Dr. Herbert Kleber of Columbia University.

Their concerns are not unfounded. Six years ago, seven people died when a New Jersey doctor attempted an earlier form of rapid detox. The doctor was brought up on charges, but a judge later ruled that the deaths were not related to the treatment.

But Bernstein said his critics just don't have all the information about this new version of rapid detox.

"When doctors don't understand things, they tend not to accept them," Bernstein said. "Once doctors learn about what the procedure is, it makes perfect sense to them," he said.

Loyd said he woke up clean and sober after the treatment, and has no complaints.

"I just want my head clear. I never, ever thought it would be clear again, never thought there was anything out there in the world that could do it without the suffering part. I don't know what the future brings, but right now I do not have a physical craving."