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The Best of Times, the Worst of TimesWhen during the day should you take your medication? Good question.

By Emily AnthesPosted Thursday, Nov. 1, 2007, at 11:13 AM ET

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Chronobiologists have tried—and failed—to change all of this. Several decades ago, Halberg led a delegation of scientists who met with FDA officials. "We recommended to the FDA commissioner that timing as well as dosing be considered in the administration of medications by a requirement in the package insert," Halberg wrote in a 2003 recounting of this effort. "The commissioner explicitly assured the delegation he would do something about it." But according to an assistant FDA commissioner who was a chronobiologist, Halberg says, after the delegation left, "the commissioner told the staff no more than to proceed with 'business as usual.' "

It doesn't help the chronobiologists' cause that they represent a small research niche in a mammoth industry. Unless drug companies think there's serious money at stake, they're unlikely to poke around in the lab just to see whether a new medication has time-related effects. Drug trials that consider chronobiology would be more complex and require more patients than the status quo. What's more, most medical professionals simply aren't aware of the extent to which the body's rhythms influence its response to medicine, Smolensky says. "There is no active conspiracy against chronomedicine," he writes in his book The Body Clock Guide to Better Health. "The biggest barrier is simply inertia."

Yet there are relatively easy ways to address the issue. Research has shown that nocturnal animals can reverse their usual biological rhythms if the rooms in which they are housed are kept relatively dark during the day and lighter at night. Drug studies should, at the very least, use animals on this adjusted schedule. Better yet, they could use two groups of rodents, a standard nocturnal set and another one on a reverse schedule. That way, scientists would be able to notice early on whether time affects how a drug works.

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When it comes to human testing, the FDA could mandate small, early stage clinical trials with different groups of patients taking a drug at least three different times of day. If a certain drug turns out to have no time-related differences, we'll be reassured that it's safe to take anytime. Nobody knows precisely how many drugs exhibit time-related effects, but the number isn't tiny. Many different kinds of medications behave this way, and how important the variations are depends on factors like the seriousness of the illness being treated and the side effects of the medication.

Yes, these changes will require drug trials that are larger and more costly. But the return on investment could be huge in some areas. For instance, doctors have already successfully begun integrating circadian rhythms into cancer treatment. Chemotherapy causes its famously debilitating side effects because the drugs used are highly toxic to healthy as well as cancerous cells. It turns out, however, that based on the circadian rhythm, doctors can administer chemo at a time when malignant cells are more susceptible to the drugs than normal ones are. Such carefully timed treatment has been shown to help patients tolerate higher doses of chemo and survive longer. Cancer has become one of chronomedicine's biggest success stories. When will we hear about the next one? The clock is ticking.

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Emily Anthes is a science writer who lives in Brooklyn, N.Y.
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