Older Than Dirt, Phentermine Works

It’s great to have new options for obesity meds. Since 2010, FDA has approved four of them. But the fact is that the mainstay of obesity meds is still something that’s older than dirt – phentermine. And new data suggests that it can work safely and effectively when used as a chronic med for this chronic disease. Just one problem remains: the FDA-approved labeling only covers short-term use.

A Study of 13,972 Patient Records

The new data comes from the PCORnet PORTAL cohort – an innovative resource for data on 12 million patients sponsored by the Kaiser Foundation Research Institute. Kristina Lewis and colleagues published their analysis in the new April issue of Obesity.

What they found was further evidence that phentermine is safe and effective for treating obesity for more than the three month treatment duration covered by its 1950s era labeling. Back then, people thought of obesity as a temporary, voluntary problem. Make up your mind to lose a little weight and all will be well. Maybe a little help from “diet pills” can get you started, but you shouldn’t really need them and had best not use them for long.

Chronic Care for a Chronic Disease

Sixty years later, obesity medicine physicians have a better understanding. Obesity is not so different from high blood pressure. The systems that regulate fat storage have gone awry in obesity. A chronic condition requires chronic care.

And that’s exactly what Lewis et al found. With short-term use, phentermine provided no lasting benefit. The body returns to a higher weight. With longer-term use, they found sustained lower weights.

Perhaps more important was the cardiovascular safety. Phentermine can cause a rise in heart rate because it stimulates the sympathetic nervous system. So the finding of no increased risk for cardiovascular events or deaths is reassuring. Regardless, though, phentermine’s affect on heart rate makes it a poor choice for people with heart disease.

Observational Data

Of course, these data are merely observational. These safety observations are not as robust as the findings of a prospective study like the Belviq CAMELLIA-TIMI 61 study. That study is what brought a recent change in the Belviq labeling to affirm its long-term cardiovascular safety. The study took hundreds of millions of dollars and years to complete.

On the other hand, a phentermine prescription can cost as little as $11 per month, according to GoodRx. The cost for Belviq is more like $305. At the high end of the range, Saxenda comes in at $1,243. If you’re lucky, not all of that comes out of pocket, but somebody is paying, so having a frugal option is helpful.

That would be why phentermine is the most commonly used prescription drug for obesity. But we need to find a way to close the gap between clinical reality and FDA labeling for this drug that reflects outdated thinking about obesity from the 1950s.

Click here for the study by Lewis et al and here for further perspective from the authors.

Pennies, photograph © Amanda Bui / flickr

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March 23, 2019