THE use of narcotic painkillers, or opioids, has boomed over the past decade as drug makers and doctors have promoted them for a new use: treating long-term pain from back injuries, headaches, arthritis and conditions like fibromyalgia. Insurers have also grown to see pills as a cheaper way to treat chronic pain than other methods.

Some patients are greatly helped by opioids, a large family of medications. Among the more widely used opioids are oxycodone, which is found in Percocet and OxyContin, and hydrocodone, which is used in Vicodin. Other potent opioids include fentanyl and methadone. Narcotic painkillers are now the most widely prescribed class of medications in the United States, and prescriptions for the strongest opioids, including OxyContin, have increased nearly fourfold over the past decade.

There is increasing evidence, however, that such drugs, along with being widely abused, are often ineffective in treating long-term pain and can have serious consequences, particularly when used in high doses. Along with the risk of addiction, side effects can include psychological dependence, reduced drive, extreme lethargy and sleep apnea.

The economic costs associated with the painkiller boom have also proved enormous, giving rise to a host of unanticipated medical, legal and social costs. Over the past decade, the legal — and illegal — use of these drugs has given birth to new businesses and expanded existing ones. These include urine-screening tests to make sure patients are taking the drugs properly, added sales of addiction treatment drugs, growing emergency-room expenses, law-enforcement budgets and skyrocketing costs for insurers.