Chronic pain – the kind that lasts for months or recursregularly – afflicts more than a quarter of adult Americans.Treating pain can be extremely challenging, however, in partbecause it can't be measured with instruments. It's in the eye – orneck or joint – of the beholder.

Doctors often prescribe powerful painkillers called opioids --natural or synthetic versions of opium. Sometimes the prescriptionis for short-term, acute pain: If you've ever had a root canal orsurgery or thrown out your back, you may have received aprescription for Percocet or Vicodin, both of which are opioidsthat also contain acetaminophen.

For people with long-term, persistent pain – often frommusculoskeletal injuries or nerve damage – opioids may be the bestoption to manage their pain and enable them to function day afterday.

But there's a hitch: Though highly effective, these drugs aredangerous and addictive. The chief danger is that they can causerespiratory depression: If too much is taken, breathing slows andmay eventually stop.

And because they cause euphoria, opioids are popular targets formisuse and abuse. In 2007, 11,499 people in the United States diedfrom opioid overdoses, according to the Centers for Disease Controland Prevention. That was more than the number of overdose deathsfor heroin and cocaine combined.

To help monitor use of the drugs, some doctors ask patients tosign "pain contracts" or "opioid treatment agreements" that spellout the rules patients must follow to take these drugs safely. Thecontracts aim to discourage people from taking too much medication,mixing medications, or sharing or selling them, among otherthings.

The agreements may require patients to submit to blood or urinedrug tests, fill their prescriptions at a single pharmacy or refuseto accept pain medication from any other doctor. If patients don'tfollow the rules, the agreements often state that doctors may dropthem from their practice.

Some patient advocates and policy experts say that rather thanensuring safety, the agreements invade patients' privacy and damagethe trust that's essential to the doctor-patient relationship.

Joan Crowley started taking an opioid in 2003 to treat recurringmigraines and an arthritis-like autoimmune disorder that caused herjoints to swell. The drug kept her pain under control and allowedher to continue her work as an accountant in the Pittsburgharea.

A few years ago, her primary-care provider asked her to sign atreatment agreement for the opioid and for Xanax, an anti-anxietydrug she also took regularly. Every three months she visited thedoctor so he could evaluate her condition and write her a new roundof prescriptions. Sometimes he did a urine test as well.

All went smoothly until this past winter. Crowley, 51, went tothe emergency room with what she thought was a heart attack butturned out to be anxiety. While there, she says, she was given ananti-anxiety drug and other medications.

The next day she had her regular appointment with her doctor,who gave her prescriptions for her regular drugs and took a urinesample. A week later, she says, she got a telephone call from him,saying that an opioid she wasn't supposed to be taking had turnedup in her urine sample. The doctor gave her 60 days to find a newphysician – even after she told him about her ER visit.

Crowley acknowledges that her relationship with the doctor hadbeen strained before that. Still, she was stunned. "This is someoneI'd been a patient of for 11 years," she says. "There was a levelof trust there."

Because of a few high-profile prosecutions of doctors forrunning "pill mills," some experts say, doctors increasingly usepain contracts to protect themselves. The subjective nature of painmakes doctors afraid they'll be scammed by unscrupulous patients,says Myra Christopher, chief executive of the Center for PracticalBioethics in Kansas City, Mo., who co-authored a recent articlecritical of pain contracts.

"Providers' primary concern ought to be the management of painand suffering," she says. "This shifts the locus of concern to theproviders' protection."

Others disagree. They say treatment agreements can function asan educational tool and a treatment road map. "It provides aframework to talk about the issues that come up in a treatmentplan," says S. Hughes Melton, a family physician in rural Lebanon,Va., where substance abuse, including addiction to pain medication,is a serious problem.

After working in the mining industry for 22 years, Jeffery Boyd,50, developed continual pain in his back and legs. Working withMelton, he manages his pain with an opioid and another drug. ToBoyd, signing a treatment agreement and being closely monitored byMelton are secondary concerns: Mostly he's just glad to have hispain under control.

"The pain won't ever go away," he says, "but [Melton] got me towhere I can work at my job and do things."

That attitude is probably shared by many people with chronicpain, say experts. "Most patients who come in, they just wantrelief," says Will Rowe, chief executive of the American PainFoundation, a consumer advocacy group. "They don't want to hearabout the public-health problem of the misuse of opioids."