Chronotherapy - Tunes In to Body's Rhythms (cont.)

"The biology of human beings is not constant throughout the day, the menstrual cycle, and the year," says Michael Smolensky, Ph.D., director of the Chronobiology Center at the University of Texas. "Instead, it varies predictably in time."

Coordinating biological rhythms (chronobiology) with medical treatment is called chronotherapy. It considers a person's biological rhythms in determining the timing--and sometimes the amount--of medication to optimize a drug's desired effects and minimize the undesired ones.

According to Smolensky, patients are more likely to follow schedules for taking their medications when those medications are formulated as chronotherapies because of better medical results and fewer adverse side effects. "With better compliance, the disease can be better contained, which means fewer doctor visits and potential trips to the hospital because of acute flare- ups," he says.

The area in which chronotherapy is most advanced--drug chronotherapy--for the most part does not involve new medicines but using old ones differently. Revising the dosing schedule, reformulating a drug so its release into the bloodstream is delayed, or using programmable pumps that deliver medicine at precise intervals are some of the simple changes that may reap enormous benefits. Drugs that are reformulated as chronotherapeutics are regulated by the Food and Drug Administration.

Here's a look at how chronotherapy is being used or studied for various diseases.


Normal lung function undergoes circadian changes and reaches a low point in the early morning hours. This dip is particularly pronounced in people with asthma.

Chronotherapy for asthma is aimed at getting maximal effect from bronchodilator medications during the early morning hours. One example is the bronchodilator Uniphyl, a long-acting theophylline preparation manufactured by Purdue Frederick Co. of Norwalk, Conn., and approved by FDA in 1989. Taken once a day in the evening, Uniphyl causes theophylline blood levels to reach their peak and improve lung function during the difficult early morning hours. There are other bronchodilators that act similarly to address the early morning dip in lung function, but the manufacturers have not sought or received FDA approval for chronotherapeutic labeling.

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