To prevent chronic problems, it is even more essential to seek medical attention as soon as possible if a significant injury occurs. Each of us has an internal clock that controls the rhythmic secretion of certain hormones as well as fluctuations in blood levels of various chemicals that can have important health effects. Some disorders tend to be worse at certain times of the day, and drugs are more effective if their administration is timed to provide the highest levels during periods when they are needed most. Heart attacks and strokes occur more often during the early morning hours when people awaken and stress hormones increase blood pressure and clotting tendencies. As a result, some medications designed to prevent such problems are given at bedtime, and have an enteric coating that allows peak strength to be reached around 6 A.M. Taking antihistamines at bedtime may provide better protection from hay fever attacks, which are often worse shortly after waking up.
Asthmatic problems are typically more frequent and more severe at night.
A dose of a bronchodilator given in the early evening can significantly reduce nighttime symptoms. Since stomach acid secretion is greatest at night, acid-blocking drugs are also more effective when taken with dinner. Conversely, toxic or side effects of drugs can be more severe during some periods of the day. Researchers are now studying whether giving chemotherapy infusions for colorectal cancer while patients are sleeping would allow them to receive higher doses because of fewer adverse reactions during this period. However, night workers may experience opposite rhythmic fluctuations.