Radical Transparency Versus Evasion on Drug Labels
Change is hard and people resist it. FDA is coming to terms with the idea of radical transparency and certainly drug labels are a good place to start. When we talk about drug labels for prescription drugs, it means the lengthy “prescribing information” that FDA reviews and approves. Its purpose is to tell doctors, pharmacists, and other health professionals everything they need to know about a drug to use it safely and effectively.
A Blind Spot on Obesity
But when it comes to information on how drugs work in people living with obesity, there’s long been a big blind spot. Peter Pitts, a former associate commissioner at FDA, points this out on RealClear Health and DrugWonks.com:
“Why does the agency require labels to include hepatic impairment pharmacokinetic information, but not information for patients with obesity – since the population of people with hepatic impairments is a twentieth the size of people with obesity?
“According to Harvard researchers, serious gaps exist in what is known about the effects of obesity on drug disposition and current label information on drug use. Why is it acceptable for these gaps to continue to exist within the universe of FDA-approved medicines and, more importantly, why do they continue to exist unexamined and uncorrected?”
Pharmacokinetics may seem like a wonky detail. But it is an essential tool for understanding how a drug acts in a person’s body. How does it get absorbed? Where does it go? How long does it stay? How fast does the body eliminate it? These are basic questions. And it turns out that the answers are different for many drugs when a person has obesity.
Too often, this fact has not made it into drug labels, as Pitts explains.
Evading the Question on Posaconazole
For some time now, we’ve been asking Merck and FDA to disclose a basic fact about posaconazole in its label. It hangs around in the body of a person with obesity longer than it does in a lean person. Studies show that the elimination half-life is between 71% and 78% longer.
FDA’s response has been to study the problem.
Merck’s response has been to avoid this fact – as if it’s inconvenient. Recently they presented data at a European conference, trying to suggest “a similar posaconazole half-life” in persons with obesity. But their data (figure 2B) shows a clear stepwise increase in retention of posaconazole over time as body weight goes up. Glossing over this evidence of an increased half-life, they conclude it doesn’t matter and that physicians can simply “follow existing guidance.”
Need to Know
In the case of posaconazole, the facts are simple. It takes longer for it to wash out of the body of a person with obesity. The half-life is more than 70% longer. Doctors who use this drug in cancer patients want to know this fact. It belongs in the label. Merck and FDA need to stop dragging their feet and make a simple change to disclose this fact in the drug’s label.
If we believe in radical transparency for drug labels, the need for action is obvious.
Click here for the post by Peter Pitts on the obesity blind spot and here for Merck’s presentation that glosses over this issue. For further background, click here.
Obscure Glass, photograph by Roman Eisele, licensed under CC BY-SA 4.0
Subscribe by email to follow the accumulating evidence and observations that shape our view of health, obesity, and policy.
April 22, 2025
