ALTERED TREOPHYLLINE CLEARANCE IN CHILDREN WITH BRONCHIAL ASTHMA WITH AN INFLUENZA VIRUS INFECTION

Theophylline is one of the most frequently administered drug in children with bronchial asthma. But, accumulation of serum theophylline during viral infections or some febril disease has been described.We studied alteration of serum theophylline concentration, theophylline clearance and urinary excretion of theophylline metabolites during influenza virus infection. The results were as follows: 1) During influenza virus infection, the first febrile day, serum theophylline concentrations were two times as much as those in a convalescent state. For the first time, serum theophylline concentrations were normal at the third day since to alleviate fever.2) The first febrile day, theophylline clearances were half as much as those in a convalescent state.3) The urinary excretion of the theophylline metabolites, 1, 3-demethyluric acid, 1-methyluric acid, 3-methylxantine, were decreased during influenza virus infection.The ratios of theophylline metabolites to theophylline in urine were decreased, too.Our study indicates that serum concentrations of theophylline are higher in children with influenza virus infection than in those in a convalescent state. The higher concentrations are due to decreased theophylline clearance. We concluded that it may be the result of depression of the metabolic activity of hepatic cytochrome P-450 enzyme system during influenza virus infection.