Eli Lilly & Co.’s blockbuster weight-loss and diabetes drugs are no longer considered to be in shortage in the US, threatening to upend the many knockoffs that became popular when patients couldn’t find the brand-name medicines.

The Food and Drug Administration said that the shortage of Lilly’s Zepbound and Mounjaro is resolved. The agency added that there are “legal restrictions on making copies of FDA-approved drugs” when there isn’t a shortage.

The FDA first put the shortage classification in place at the end of 2022. That designation allowed compounding pharmacies to sell knockoff versions of the brand-name medicines—Mounjaro for diabetes, and Zepbound for obesity—without completing the same arduous testing process. These copycats have been widely available from medical spas and telehealth companies, often at a much lower cost.

Meanwhile, Lilly has been investing heavily in manufacturing to boost supply of the popular shots and aggressively tried to limit compounded versions of the drugs, raising concerns about quality and saying some were contaminated with bacteria or chemical impurities. Compounders have said they follow regulations and make high-quality drugs.

The drugmaker said that while all doses of Zepbound and Mounjaro are available, the supply chain for refrigerated medicines is complex and patients’ ability to find particular doses in pharmacies may still vary.

“We know many people rely on our medicines, so we invested significantly to expand manufacturing and bring new options to the market,” Patrik Jonsson, executive vice president and president of Lilly Cardiometabolic Health and Lilly U.S., said in an emailed statement.

Experts estimate that hundreds of thousands of Americans have used copycat versions of Lilly’s medicines or similar shots from Novo Nordisk A/S, which have also been in short supply. Overall, makers of such compounded drugs are bringing in as much as $1 billion a year, according to investment bankers who work with the industry.

Compounding also attracted telehealth companies that marketed services to connect patients with health-care providers who can prescribe the drugs.

The end of the shortage is likely to limit future compounding but some may be allowed to continue under other U.S. policies.

The FDA’s announcement doesn’t mean that the drug will always be available everywhere.

“Patients and prescribers may still see intermittent localized supply disruptions as the products move through the supply chain from the manufacturer and distributors to local pharmacies,” the agency said.

2024 Bloomberg L.P. Distributed by Tribune Content Agency, LLC.