RESUMEN
The relationship of theophylline concentration in serum and saliva was studied in 10 Thai asthmatic children receiving “Elixir Quibron” and Tablet Aminophylline orally in a cross over design. There was an excellent linear relationship between theophylline concentration in serum and saliva regardless of dosage forms. Proportionality factor that relates saliva to serum concentration obtained in this study was 1.60. Serum Theophylline concentration can be estimated by analysis of saliva concentration multiplied by 1.60. These observations suggest that determination of theophylline concentration in saliva is an effective, convenient, noninvasive, and painless method for routine indirect monitoring of serum theophylline concentration in Thai asthmatic children.