The legislation earned quiet endorsement from the Biden administration and a solid group of Democratic votes, but exposed divisions over how to tackle the country’s most pressing drug crisis.The House of Representatives passed legislation on Thursday that would make permanent harsh criminal penalties and strict controls on fentanyl-related drugs, with scores of Democrats joining nearly all Republicans in a vote that reflected the political challenges of tackling what both parties consider America’s most pressing drug crisis.The bill, approved by a vote of 289 to 133, would permanently list fentanyl-related drugs as Schedule I controlled substances, a designation that mandates severe prison sentences for highly addictive, nonmedicinal chemicals, and which is now set to expire at the end of 2024.The bipartisan vote reflected agreement among Republicans and a solid bloc of Democrats that stiffening penalties for fentanyl-related drugs is a necessary component of the federal response to the crisis. According to the Centers for Disease Control and Prevention, fentanyl-related drugs were the cause of most of the roughly 75,000 synthetic opioid overdose deaths that occurred in 2022.“We should vote to advance this bill that we agree on and that does help stop the bad guys,” Representative Morgan Griffith, Republican of Virginia and an author of the bill, said on the House floor. “Once fentanyl analogues are permanently made Schedule I, Congress can build off this and deal with the illicit crisis.”But there are deep divisions over the ramifications of doing so, making the fate of the legislation unclear in the Democratic-led Senate.Many Democrats, along with public health and civil rights groups, note that harsh sentences for fentanyl-related drugs have driven up incarceration rates and disproportionately affected people of color. They argue that further criminalizing them will only worsen the crisis and have called for a public health response including better public education, more addiction treatment and recovery services, as well as overdose prevention.The White House last week came out in support of the House bill, while urging that Congress consider its other recommendations, including narrower mandatory minimum sentences that would apply only to cases in which the substance could be linked to death or serious bodily injury.But on the House floor on Thursday, Representative Frank Pallone Jr. of New Jersey, the top Democrat on the Energy and Commerce Committee, broadly denounced the G.O.P. bill, calling it “one-sided” and a futile attempt “to incarcerate our way out of a public health crisis.”“This war on drugs — mandatory sentencing, incarcerate everybody — has not worked,” Mr. Pallone said. “It didn’t work on other drugs.”Still, a large group of Democrats, some of them from competitive districts, lined up in support of the measure, eager to show they were working to tackle the synthetic opioid crisis at a time when Republicans have attempted to portray their party as weak on the issue.Representative Angie Craig of Minnesota, one of the 74 Democrats to cross party lines and support the bill, said she was “not going to let perfect be the enemy of good here.”“We’ve got an American crisis here at hand, and I think what you saw from the White House is that they recognize this is a crisis,” Ms. Craig said, noting Thursday’s bill “is what can pass the House, and we’ll see what happens in the Senate.”The debate was just the latest and most focused fight to play out over fentanyl in Congress, where the synthetic opioid crisis has featured prominently in other politically charged policy battles, such as how to address rising threats from China, and a bitter standoff over border security and immigration. Republicans in particular have frequently cited the surge of fentanyl-related deaths across the country as a reason to clamp down on immigration and impeach Alejandro N. Mayorkas, the homeland security secretary, even though the bulk of such drugs are brought in through ports of entry by U.S. citizens.Under Schedule I, a person caught trafficking 10 grams of fentanyl would receive a minimum prison sentence of five years, while a person carrying 100 grams would receive a minimum sentence of 10 years. According to the Drug Enforcement Administration, with some fentanyl analogues, a few milligrams can be a deadly dose.The legislation makes exceptions for drugs already listed elsewhere — such as fentanyl itself, which, as an ingredient in various federally approved medicines, appears on Schedule II — and for institutions researching fentanyl analogues for potential beneficial use.But Democrats raised concern that the bill contains no instructions for delisting fentanyl-related drugs later found to be beneficial, or reducing or vacating the sentences of people convicted of related offenses.A companion bill in the Senate so far has only Republican backing, and Democratic leaders were unsure how many of their members might back the effort — particularly after the White House statement supporting it.The administration has proposed coupling the permanent Schedule I designation of fentanyl-related drugs with the narrower application of the mandatory minimum sentences, as well as a mechanism for delisting fentanyl-related drugs discovered to have medicinal properties and for reducing or vacating any related criminal sentences. It has also called for a study of how the permanent scheduling would affect research, civil rights and the illicit production and trafficking of fentanyl analogues.Many of those proposals have been included in bipartisan bills still pending in Congress.