[Day-night pattern of bronchial width and dyspnea: basis for selection of optimal dosage schedules for theophylline].

Asthma typically worsens overnight. Although 24-hr variation in environment conditions may contribute to the worsening of dyspnea at night, this does not fully explain day-night patterns of this disease. Circadian (about 24-hr) rhythms in bioprocesses which influence airways patency constitute major contributory factors. The nighttime exacerbation of asthma may represent the influence of circadian bioperiodicities in bronchial patency, airways hyperreactivity to acetylcholine, histamine and house dust, and altered levels of several plasma constituents such as cortisol, adrenaline, histamine and cyclic AMP.