ABSTRACT
Theophylline is a useful drug in the treatment of respiratory diseases with bronchospasm but it has very narrow safety margin. The study was carried out in 44 admitted Thai children with plasma theophylline levels > 20 microg/ml to determine the association between blood levels and symptoms of theophylline toxicity. The prevalence of theophylline toxicity (plasma theophylline level > 20 microg/ml) in Thai children is about 11%. Thirty-four percent of the patients who had theophylline levels less than 30 microg/ml and 78% of those who had levels more than 30 microg/ml had symptoms of theophylline toxicity. The symptoms were related to the gastrointestinal tract (34%), cardiovascular system (18.2%), neurological system (6.8%) and metabolism (54.5%). The possible causes of theophylline toxicity were respiratory tract infection, theophylline overdosage, interaction with other drugs, impairment of liver function, congenital heart disease and theophylline usage in neonates. Theophylline is still a useful drug but should be used with caution. Theophylline levels should be checked in every child who receives theophylline.