Leaving Doctors in the Dark About Patients with Obesity
In some ways, it is nothing new. The medical needs of people living with obesity have been dismissed seemingly forever. But at the same time it is shocking to learn of Merck – a highly respected pharmaceutical firm – leaving doctors in the dark by choice about how one of their drugs acts differently in patients with obesity.
Stat News reported yesterday that Merck “has refused to update the language” in labeling for one of its drugs to disclose this difference.
Interactions Between Posaconazole and Cancer Drugs
The drug is posaconazole – an antifungal that persons in treatment for cancer may need when a fungal infection develops. Doctors and pharmacists know quite well that it interacts with many drugs used for cancer – interfering with their metabolism. Those interactions can become quite serious.
What is not widely known, though, is that posaconazole hangs around in a person’s body much longer if that person has obesity. The prescribing information (the drug labeling) for posaconazole says its elimination half-life is 27 hours. This is the most common measure of how long it takes for a drug to clear from a person’s body.
Researchers have shown that for people with obesity, the half-life is much longer. In a 2018 study, researchers showed that its half-life was 78% longer for these people. What that means is that posaconazole can linger much longer to interact with other drugs if a person has obesity – even if the patient has stopped receiving posaconazole.
Clearly, this is an important fact to know for a doctor using this drug.
Information That Belongs in the Label
Merck responded to Stat by saying that the company believes drug interactions for posaconazole are “currently well-described in the medicine’s labeling.” But the labeling makes no mention of the extended half-life.
Harvard Professor Caroline Apovian, a past president of the Obesity Society, will be presenting research relevant to this at ObesityWeek. She and colleagues found that many oncologists are unaware of posaconazole’s extended half-life, but they believe it is important information that belongs in the drug label. She explained:
“In obesity, since the half-life of posaconazole is prolonged, you have to wait longer before starting chemo agents. Why do you have a wash-out period? You have a wash-out period because posaconazole interferes with absorption and metabolism of chemo agents. You need a longer wash-out period for those with obesity. And this is not in the label.”
Obesity medicine physician Fatima Cody Stanford expressed frustration with Merck’s reluctance to disclose this important information:
“The question is why not make the labeling change? It won’t harm anyone by making the change and could prevent harm. But there’s a lack of transparency and we’re forgetting about the idea of preventable harm when we think about the labeling change. The pharma industry doesn’t really care about this patient population … unless there’s a really significant adverse event, such as death.”
Intransigence and Apparent Indifference
We cannot fathom the intransigence of Merck on this subject, leaving doctors in the dark. A simple disclosure of the scientific fact regarding an extended half-life is all it takes to arm doctors and pharmacists with information that could help them avoid a preventable harm. This seems like nothing short of indifference to the health and safety of persons with obesity.
Click here for the article in Stat News and here for the position statement of all the major obesity organizations on closing this gap in drug research and labeling. For a call to action on this issue from the American College of Clinical Pharmacology, click here.
High Trestle Trail Bridge, photograph by Tony Webster / Wikimedia Commons
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October 29, 2024
