What to know about Mounjaro, the next game-changing medication awaiting FDA approval to treat weight loss

• Tirzepatide, a medication approved to treat diabetes, helps aid weight loss by lowering appetite.
• A similar drug called semaglutide was approved for obesity and became so popular it caused shortages.

Another weight loss medication designed to treat diabetes is part of a promising class of new drugs that may aid weight loss.

Tirzepatide, sold under the brand name Mounjaro, has attracted attention for dramatic weight loss results, including a clinical trial that found patients lost 20% of their body weight in 16 months while using it.

The study results are a game-changing level of weight loss typically unheard of without weight loss surgery, Dr. Robert Gabbay, chief scientific and medical officer for the American Diabetes Association, told USA Today.

Despite its potential, there are a lot of unknowns about the future of the drug, including access for patients, according to an obesity medicine expert.

Here's how tirzepatide works, how its prescribed, and possible downsides, including side effects, cost, and insurance issues.

It's not yet approved for weight loss, but doctors can prescribe it

One of the most popular existing weight loss drugs, called semaglutide, originated as a diabetes medication, and was FDA-approved to treat obesity in 2021, becoming so popular it caused shortages.

A similar story may unfold with tirzepatide: although it hasn't been approved by the FDA for weight loss, treatment providers anticipate that will change, based on research showing its potential for patients with obesity.

"We do expect that it will be approved for the treatment for obesity," endocrinologist and obesity medicine specialist Dr. Scott Isaacs told Insider, although it's not clear how soon.

In the meantime, patients can still access the drug. The lack of FDA approval for weight loss means manufacturers aren't able to market the drug for weight loss, Isaacs said. Since tirzepatide is already FDA-approved for use with diabetes, doctors are able to prescribe it to patients, even for a different purpose, if they think it will help.

It helps reduce appetite, similar to drugs like semaglutide

Tirzapetide works in the same way as other diabetes medications used to treat obesity, according to Isaacs.

"It's more similar than different to other drugs," he said.

It acts on a hormone called GLP-1, which controls appetite, so patients taking the drug feel more full. Tirzapetide uniquely also acts on another hormone related to insulin too.

Some research has claimed that tirzepatide is more effective for weight loss than other medications, based on a clinical trial showing more pounds lost.

But Isaacs said evidence is inconclusive, since the study was designed to focus on diabetes, not weight loss, and didn't use the strongest available dose of semaglutide.

"It's considered more effective but how much more, no one really knows," he said.

As with similar drugs, tirzepatide can cause side effects like nausea.

It may be difficult to afford long-term

One of the biggest questions about tirzepatide right now is if it will be affordable and accessible to patients who need it over time.

Typically, the high cost of weight loss drugs can be a deterrent to patients. Semaglutide, for instance, has been listed at a price of $1,349 for a month's supply for obesity treatment.

A majority of insurance plans don't cover weight loss medications, and those that do require extensive paperwork, according to Isaacs.

"It's a huge burden to prove patients qualify for the drug," he said.

Tirzepatide is gained popularity as a weight loss prescription because of a discount that maked the drug available at $25 for a one to three months supply, according to the manufacturer's website. Now that discount is only available to those with type 2 diabetes.

The catch with weight loss medications like tirzepatide and semaglutide is that patients have to continue taking the medication to maintain the weight loss.

"We do want to use the drugs long-term because we know if they stop taking them, the weight comes back on," Isaacs said.

However, the discount is slated to expire next year, so patients taking tirzapetide will need to find another means to afford the drug.

"There's a lot of unknowns. We do our best, and there's hope things will change," Isaacs said. "I'm very up front with patients but I do worry come June next year."