Tuning Meds to Your Body Clock

Oct. 4, 2002 -- The human body's chemical ebb and flow, part of the 24-hour cycle known as the circadian rhythm, is now the focus of researchers who are trying to use the cycles to improve medical therapy.

Most of us are already aware of some of the ways time affects how people feel. Jet lag is a prime example, as your regular sleep cycle struggles to keep pace with adjusted bedtimes.

Yet there are many other physiological changes that take place on a daily basis that can affect your health. In fact, some of the changes experienced by the body during a 24-hour cycle are so predictable, some researchers have catalogued the effects.

For example, peptic ulcers and asthma attacks are most likely to flare up during the overnight hours, symptoms of osteoarthritis worsen over the course of the day and skin sensitivity to allergies is highest in the late evening.

"When these patterns were recognized, research was done into the biological rhythms that take part in the pathology of the disease process," says Michael Smolensky, a professor of environmental physiology at the University of Texas, Houston, and author of The Body Clock Guide to Better Health.

"Many researchers and pharmaceutical companies realized in the 1980s that by dosing medications in synchrony with rhythms in these processes that they could optimize the therapeutic benefit of medications."

Time to Heal

The time-based approach to disease treatment is known as chronotherapy, in which medications are prescribed to be taken at specific times in synchrony with the body's circadian rhythms.

Asthma treatments and heart medications have been developed with an eye on your body clock. And the approach may also help minimize the potentially toxic side effects of drugs, such as those used to treat cancer.

For instance, at a cancer clinic on the outskirts of Paris, Dr. Francis Levi equips colon cancer patients with portable, computerized pumps programmed to dispense chemotherapy drugs at specific times.

In this case, the peak dosage for most of the drugs has been scheduled for 4 a.m., while the patient is at home, asleep.

"This is a time when cancer cells are vulnerable to chemotherapy but also when normal, healthy cells best tolerate the treatments," Levi explains.

In published studies, researchers found that compared to traditional chemotherapy, which is given at a steady dose without regard to time of day, better results are achieved by using the portable pump and actually scheduling a cancer drug to the body's cycles.

Patients tolerated 40 percent more of the drug, while the number of patients with significant tumor shrinkage doubled and common side effects of chemotherapy, including nausea, mouth sores and fatigue, were all reduced.

"Fewer side effects experienced by the patients meant that it was possible to treat [cancer] more aggressively than if the drugs were given without any consideration for the biological rhythms and tolerance," says Smolensky.

Gaining Ground

While it is not a new concept, chronotherapy has been slow to take off in the United States.

"It's an area that has been in development in the United States with a great amount of research, but American doctors have been more engendered to the concept of homeostasis — that the body is relatively constant in its functioning," says Smolensky.

Chronotherapy has achieved more widespread acceptance overseas. At least 40 cancer clinics in Europe now use the body's circadian rhythm to determine when to administer chemotherapy.

Most American hospitals are waiting for more evidence, which may soon be available. A large-scale survival study of 564 patients funded by INSERM, the French equivalent of the National Institutes of Health, has just been completed and the results are expected next year.

ABCNEWS' Melinda T. Willis contributed to this report.