Currently, the drug also can be prescribed for moderate pain.
U.S. Reps. Hal Rogers, R-Ky., and Frank Wolf, R-Va., cited recent admissions that OxyContin was highly addictive.
The May 16 letter to FDA Commissioner Andrew von Eschenbach pointed to OxyContin's maker, Purdue Pharma L.P., and three of its current and former executives who recently pleaded guilty to misleading the public about the drug's risk of addiction.
"The admission of guilt demands your immediate response by reclassifying this potent medication and sending a message to doctors on the potentially lethal aspects of this drug and its correct and appropriate employment," the letter says.
OxyContin has been blamed for hundreds of deaths across the country in recent years, known as "hillbilly heroin" in drug-ridden Appalachia states like Kentucky, Virginia and West Virginia.
An FDA spokeswoman did not have an immediate response.
Rogers and Wolf have fought for tougher regulations over the drug for years, calling for a federal investigation into the manufacturer's marketing practices in 2001.
A 2003 report by the Government Accountability Office found that Purdue Pharma sent doctors videos that made unsubstantiated claims minimizing the dangers associated with the drug.
At the time, Rogers and Wolf insisted that FDA reclassify OxyContin's prescription from a "moderate-to-severe" to "severe-only" pain designation.
"FDA rejected this request," the letter says, even as the prevalence of the drug "overwhelmed" law enforcement, local communities and drug treatment, according to the letter. The May 11 plea agreement requires Purdue Pharma, its president, top lawyer and former chief medical officer to pay $634.5 million in fines for claiming the drug was less addictive and less subject to abuse than other pain medications. It settled a national case and came two days after the Purdue Pharma agreed to pay $19.5 million to 26 states and Washington, D.C., to settle complaints that it encouraged physicians to overprescribe OxyContin.