Over the past year, the injectable diabetes medication Ozempic steamrolled through TikTok, talk shows, and tabloids as people raved about using it off-label to lose weight. Then the hype intensified in the fall around Wegovy, a similar medication approved for weight management.
Another diabetes drug, called Mounjaro, is now gaining attention, with many people using it off-label to lose weight. Some research has found that Mounjaro maybe even more powerful than either Ozempic or Wegovy. One major study comparing these drugs found that taking tirzepatide, the active ingredient in Mounjaro, led to sharper reductions in blood sugar levels and greater weight loss than the other drugs.
However, that study compared different doses of semaglutide and tirzepatide, making it tricky to determine how these medications stack up head-to-head, said Dr. Dean Schillinger, a professor of medicine and a diabetes expert at the University of California, San Francisco. It was also sponsored by Eli Lilly, the company that manufactures Mounjaro.
Mounjaro is approved by the Food and Drug Administration to treat only Type 2 diabetes. “Mounjaro is not a weight loss drug,” the official website for the medication reads, under larger, bold purple letters proclaiming that people taking it have lost up to 25 pounds. But there is some speculation that the FDA could authorize the medication for weight management soon; Eli Lilly announced in October that the FDA had fast-tracked its process of examining and approving tirzepatide for adults who are obese or overweight.
“The FDA generally cannot confirm, deny or comment on a pending/potential product application,” a representative of the agency wrote in an email.
Demand is mounting: After a two-month shortage, Mounjaro is largely back in stock, although many diabetes patients are struggling to access it, said Dr. Andrew Kraftson, a clinical associate professor in the division of metabolism, endocrinology and diabetes at Michigan Medicine. Kraftson frequently urges patients looking for Mounjaro to try calling different pharmacies, he said, adding that he has had to adjust some doses to stretch out the medication.
“It’s definitely frustrating for patients and also burdensome for physicians,” he said. And as more people turn to the medication for weight management, Mounjaro could potentially surpass Ozempic in media attention and sales.
“I don’t think Blockbuster would be underselling it,” Kraftson said.
How does Mounjaro work?
Tirzepatide mimics two hormones naturally produced in the body: glucagon-like peptide-1, or GLP-1, and glucose-dependent insulinotropic polypeptide.
Ozempic and Wegovy simulate only GLP-1, whereas tirzepatide imitates both hormones. Researchers believe tirzepatide may be so effective at lowering blood sugar levels and inducing weight loss because the two hormones it imitates work in a synergistic way.
Like semaglutide, tirzepatide slows the emptying of the stomach, making people feel full for longer, said Dr. Janice Jin Hwang, the division chief of endocrinology and metabolism at the University of North Carolina School of Medicine. Tirzepatide also inhibits the brain’s hunger signals, suppressing appetite.
Research presented at an American Diabetes Association conference this past last summer showed that study participants, who did not have diabetes, taking tirzepatide lost up to 22.5% of their body weight after 72 weeks — a dramatic reduction that’s nearly as effective as weight loss surgery, said Dr. Robert Gabbay, the chief scientific and medical officer of the association.
But it’s not yet clear what the long-term effects of taking Mounjaro might be — a pressing issue, given that people need to keep taking the drug for continued results, said Akshaya Srikanth Bhagavathula, a postdoctoral fellow at the University of Arkansas who has studied tirzepatide.
Is it safe to take Mounjaro for weight loss?
Taking Mounjaro may lead to more severe side effects than Ozempic and Wegovy, as well as more significant weight loss, Bhagavathula said. People using the medication commonly experience nausea, vomiting, diarrhea and stomach pain; in rare cases, taking the drug can lead to renal failure, pancreatitis, hypoglycemia, and gastrointestinal bleeding, he added.
There isn’t robust research examining how tirzepatide might affect people who do not have diabetes or obesity. “We just don’t have enough information to inform the individual on what gamble they’re making,” Schillinger said.
Those who do take the medication need to be under close medical supervision, Kraftson said, partly because there is a risk that extreme lack of appetite could lead to malnourishment and disordered eating. “We do not want to make people anorexic,” he said. “The goal is not to get rid of all hunger.”
In a statement, a representative from Eli Lilly said that “Mounjaro is only approved for the treatment of Type 2 diabetes as an adjunct with diet and exercise,” adding, “Lilly does not promote or encourage the off-label use of any of our medicines.”
But experts warned that the more drugs like Mounjaro and Ozempic continue to gain popularity for their weight loss effects, the more patients with diabetes may be left scrambling.
“We’re going to probably watch this movie again,” Gabbay said.
This article originally appeared in The New York Times.