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Acute and chronic theophylline therapy in exercise-induced bronchospasm
Insights
Theophylline effectively reduced exercise-induced bronchospasm (EIB) in children with asthma. No tolerance developed with prolonged use, but responses varied significantly among individuals.
Area of Science:
- Pediatric Pulmonology
- Pharmacology
- Asthma Research
Background:
- Exercise-induced bronchospasm (EIB) is a common condition in children with asthma.
- Theophylline is a bronchodilator used to manage asthma symptoms.
- The effectiveness and tolerance of theophylline for EIB require further investigation.
Purpose of the Study:
- To assess theophylline's efficacy in mitigating EIB in children.
- To determine if tolerance to theophylline develops with continuous, long-term use.
- To explore the relationship between theophylline's effect on EIB and perennial asthma control.
Main Methods:
- A standardized treadmill exercise test was administered to 21 children (7-16 years) with perennial asthma.
- Pulmonary function tests (FEV1, FEF25-75%, PEFR) were measured before and after exercise.
- Tests were conducted before theophylline, 90 minutes after a single dose, and after three weeks of continuous theophylline treatment.
Main Results:
- Theophylline successfully inhibited EIB in 20 out of 21 subjects.
- Significant inter-individual variability in response to theophylline was observed.
- No tolerance to theophylline's anti-EIB effects was noted after three weeks of treatment.
- Theophylline controlled perennial asthma in all subjects, with therapeutic blood levels achieved.
Conclusions:
- Theophylline is effective in reducing EIB in children, though responses vary.
- Prolonged theophylline use does not lead to tolerance for EIB.
- EIB and perennial asthma may have distinct underlying mechanisms.
- Theophylline's effectiveness in controlling perennial asthma does not predict its efficacy for EIB.
Abstract:
This study examined the effectiveness of theophylline therapy in modifying exercise-induced bronchospasm (EIB) in children with perennial asthma and evaluated whether tolerance to theophylline developed with prolonged use. Twenty-one children between 7 and 16 years of age were studied by a standardized treadmill exercise test carried out before administration of theophylline, 90 minutes after administration of theophylline, and again after three weeks of round-the-clock theophylline treatment. Changes in forced expiratory volume at one second, forced expiratory flow between 25% and 75% of vital capacity, and peak expiratory flow rate were measured before and after each exercise test. Theophylline inhibited EIB in 20 of 21 subjects. There was considerable intersubject variation in the response to theophylline, however, ranging from complete inhibition in five subjects to no inhibition at all in one subject, even though theophylline controlled perennial asthma in all subjects, and all but one had theophylline levels between 10 and 22 microgram/ml when tested. On repeated testing after three weeks of therapy, no tolerance developed to theophylline. These findings suggest that EIB and perennial asthma may result from different causes and tha theophylline's ability to control asthma will not predict its effect on EIB. Subjects who have severe EIB should be retested after theophylline pretreatment of evaluate the effectiveness of therapy.