Consider two drugs that relieve severe pain. There's no evidence that either one works better or is safer than the other. But one is much more expensive. If tax dollars are buying one of these painkillers, which should it be?

Alternatives: Every day doctors prescribe controlled-release (CR) oxycodone (better known by the brand name OxyContin) instead of comparable but cheaper alternatives. Since state Medicaid programs often cover medications for low-income patients, several states have set policies to deter physicians from prescribing the expensive drug.

How well do such policies work? That was the focus of a study led by Nancy Morden, M.D.,M.P.H., a family physician and outcomes researcher at Dartmouth. "For most drugs," says Morden, prior authorization, the term for such policies, "is highly effective." But, she and her coauthors reported in Medical Care, this drug seems resistant to prior authorization.

Strict: Between 2001 and 2004, 21 states implemented prior authorization for CR oxycodone. Twelve set strict policies, such as requiring a phone call from the physician. Nine had more lenient policies; the right phrase on a prescription might be sufficient. In the aggregate, strict policies seemed to work better, resulting in a 34% drop in oxycodone use. Several states with lenient policies, however, saw an increase in use, and only a few saw a big decrease. Nationwide, CR oxycodone use among Medicaid beneficiaries grew 66% a year from 1996 to 2002.

In the end, the policies didn't cut costs. On average, states saw only a 31c drop per daily dose of long-acting opiates—not much given the price gap between CR oxycodone and its alternatives. In 2004, the average wholesale cost of a daily dose of CR oxycodone was $10.18, versus $4.90 for sustained-release morphine and 45c for methadone.

Cost: "There are prescription drugs that really pay off in the short term and the long term," says Morden. "There are prescription drugs that aremaybe good for society but [that don't] save money downstream, and that's okay. . . .And then there are prescription drugs that just cost us . . . [that are a] waste of money." Morden puts CR oxycodone in the last category.

She's not sure why prior authorization didn't work but thinks patients may be loyal to the OxyContin brand and doctors may resist restrictions on pain management. OxyContin's value as a street drug may be a factor, too. And she and her coauthors believe misleading marketing plays a role. In 2007, OxyContin's manufacturer was fined $600 million and "pled guilty to a felony count of misbranding a drug with intent to defraud," according to the Food and Drug Administration.

Tax: "How much of our money should we spend on oxycodone," Morden muses, a note of frustration in her voice, "given that there is no literature to support it as being in any way at all superior to the generic cheaper products on the market? . . . Should your tax dollars pay for even one of these pills?"