While fentanyl is a Schedule II drug, fentanyl-related substances have been classified under Schedule I since 2018, but the scheduling is temporary and will expire on Dec. 31, 2024.

Schedule I drugs are deemed to have no accepted medical use and have a potential for abuse and come with stricter criminal penalties for offenses.

House Republicans who proposed the bill argue that if the scheduling order expires, fentanyl-related substances will become street-legal, law enforcement will lose certain seizure authorities and drug traffickers will feel empowered to push the drugs.

On Monday, the Biden administration called on Congress to pass the bill “to improve public safety and save lives.”

As the vote approaches, 158 related organizations sent congressional leaders a letter Tuesday urging them to vote down the bill as flawed legislation and put the focus on harm reduction services and substance use disorder treatment.

The groups argue that by labelling all fentanyl-related substances as a Schedule I drug will put restrictions on research on the therapeutic potential of these narcotics, including at least one that may be an opioid antagonist similar to naloxone, which is used to counteract opioid overdoses.

They continue that while proponents of the bill argue that it expands minimum criminal penalties to deter foreign import of fentanyl-related substances, this is not the case as it also expands mandatory penalties for domestic drug offenses, including nonviolent drug distribution of small quantities.

“By automatically scheduling a huge swathe of substances in one fell swoop, the HALT Fentanyl Act would lead to very real criminal justice consequences, posing an unacceptable risk of unnecessary incarceration for substances that carry no potential for abuse,” they said, while highlighting that some fentanyl-related substances are inert or harmless.

The groups compared legislation to U.S. policy of the 1980s that saw severe mandatory minimums applied for small amounts of crack cocaine, which resulted in the disproportionate incarceration of people of color for small amounts of the drug.

“The emergence of fentanyl-related substances in recent years has fueled similar waves of alarmist media and law enforcement headlines that are informed by mythology rather than science,” the groups wrote. “Any further extension of the class-wide scheduling policy threatens to repeat past missteps with crack cocaine that policymakers are still working to rectify.”

Hundreds of thousands of people have died from overdoses during the opioid epidemic.

According to the U.S. Centers for Disease Control and Prevention, between 1999 and 2020, more than 564,000 people died from an overdose involving any opioid.

Since about 2013, the epidemic has been fueled by synthetic opioids, particularly illicitly manufactured fentanyl.

The GOP Doctors Caucus held a press conference outside of the Capitol building in Washington, D.C., urging Congress to pass the bill while framing the epidemic as an immigration issue that President Joe Biden can confront by securing the southern border.

“We’re going to continue to stand up for those families who are sick and tired of having their sons and daughters not wake up, never to wake up again, because they took a pill and next thing you know, they’re dead,” House majority leader Steve Scalise, R-La., told reporters.