In treating asthma, the circadian rhythms of the lung's airways are now taken into consideration when giving the drug theophylline, used to open airways. Researcher Jay Grossman, M.D., of Albany Medical College observed that circadian rhythms may underlie nocturnal asthma. But, while a healthy person's airway openness varies up to only about 8 percent, that of an asthma sufferer can vary up to 50 percent. Grossman theorizes that because asthmatic airways react more strongly to many different stimuli that constrict airways, they also react more strongly to circadian factors responsible for the daily variation in airway openness. This knowledge is beginning to be applied to the way theophylline is given.
Theophylline is a tricky drug.
Because the toxic dose can be close to the therapeutic dose, monitoring the patient's blood levels of the drug is standard practice. Finding a time when a larger dose could be given more safely, or when a smaller dose would be more effective, therefore, would represent an important step forward in therapy. Robert Donohoe, M.D., a consultant to FDA on the approval of theophylline products, says that recent human trials of theophylline formulations have shown that the same dose of the drug given to the same patient may act differently at night than during the day. This information has led some doctors to alter the dosing regimen for sustained-release theophylline from two divided doses daily to one dose in the evening. This is particularly effective for patients whose asthma symptoms wake them in the middle of the night or early in the morning.