Decreased theophylline clearance in children with acute asthma with concurrent febrile respiratory infection

: Elevated serum levels of theophylline, a first-line anti-asthma drug, are sometimes associated with febrile respiratory infection (FRI). Although it seems to be wellknown, conflicting reports still appear in journals. We studied retrospectively theophylline clearance (th-cl) in 74 episodes of acute asthma (44 with and 30 without FRI, in patients aged 12-mos.-13-yrs.) and tried to reveal the effect of fever or pathogens on th-cl. Th-cl was estimated by a single sample technique during intravenous drip infusion of aminophylline. The results were as follows: 1) Forty four episodes with FRI included 20 viral, 10 bacterial and 2 Mycoplasma pneumoniae infections (Table 2). 2) Th-cl in 44 episodes with FRI was significantly lower than in 30 without FRI (p < 0.001). 3) Decreased tendency of th-cl in episodes with viral infection was observed, but statistically it was not significant (p < 0.1). However, the differences of th-cl among 9 pair-cases with and without viral infection were quite clear (p < 0.01). 4) Th-cl in episodes with 10 bacterial and 2 Mycoplasma infections was reduced significantly (p < 0.01). 5) There was no difference in th-cl between episodes with viral, and bacterial or Mycoplasma infections (p < 0.1). As a result, it is suggested that fever, regardless of its origin, may decrease th-cl in acute asthma with FRI.