A year after a meningitis outbreak from contaminated pain injections killed at least 64 people and sickened hundreds, Congress is ready to increase federal oversight over compounding pharmacies that custom-mix medications.

Before the bill reaches President Obama’s desk, it must clear a hurdle put in its path by Sen. David Vitter (R-La.) in his effort to discredit the president’s health-care overhaul. A test vote is set for Tuesday evening.

The legislation, passed by the House in September, also creates a national system for tracking prescription drugs from manufacturers to retail pharmacies, first through serial numbers on bottles and containers and later through electronic codes.

Although the bill enjoys nearly universal support in Congress, Vitter has objected to the Senate voting on it without first voting on his measure to make lawmakers disclose which of their aides are signing up for health insurance through the Affordable Care Act, and which are instead being allowed to remain in the Federal Employee Benefit Program.

Vitter objects to an Obama administration decision this year allowing lawmakers to choose between the two programs for their aides, and directing the government to pick up three-fourths of the premium costs for members of Congress and their aides either way. Lawmakers must switch to coverage under the health-care law. Vitter’s insistence on ending the employer match this year prompted Senate Democrats to scuttle an energy bill. The issue arose again in last month’s fight over the government shutdown.

The compounding pharmacy bill is intended to avert a repeat of last year’s meningitis outbreak associated with the now-closed New England Compounding Center. Subsequent inspections found unsanitary conditions at the company’s plant in Framingham, Mass., including mold and standing water.

Contamination problems with compounded medicines have been reported for decades. But jurisdiction over them has been murky. Pharmacies are typically regulated through state boards, but the Food and Drug Administration regulates manufacturers of medicines.

The bill tries to sort out that legal gray area, which allowed the New England site and other pharmacies to skirt both state and federal regulations. The measure clarifies the FDA’s authority to shut down pharmacies that become so large they resemble manufacturers, but it doesn’t require those pharmacies to register with the agency, a step that would have subjected them to higher quality standards and inspections. Instead, pharmacies can volunteer to be regulated by the FDA as a sort of optional “stamp of approval.”

Still, public safety advocates who lobbied for the bill say it improves the status quo.

“It’s not as far reaching as some of the other proposals Congress considered over the past year, but it is an important step forward,” said Allan Couckell, director of the Pew Charitable Trusts’ medical group.

The FDA gets explicit authority under the bill to intervene when compounders are mass-producing medications without prescriptions or are compounding copies of widely available drugs. Compounding pharmacies can elect to register as “outsourcing facilities” subject to FDA oversight or continue to be regulated by state pharmacy boards.

The voluntary nature of a new class of pharmacies has drawn criticism from both safety advocates and compounding lobbyists, who are seldom on the same side of an issue.

The compounding industry’s chief lobbying group, the International Academy of Compounding Pharmacists, said the bill would not stop pharmacies like the one that caused last year’s outbreak, and would lead to more confusion over how compounders are regulated.

The consumer advocacy group Public Citizen, a longtime critic of both the FDA and drug companies, said the bill should have required mandatory labels on compounded drugs warning that they have not been approved by the FDA.

About 7,500 pharmacies in the United States specialize in compounding medications, though many thousands more perform a small amount of compounding while also dispensing traditional prescription drugs. Compounded drugs account for an estimated 3 percent of all prescriptions filled.

— Associated Press