Relationship between plasma and stimulated-saliva concentrations of theophylline in asthmatic children.

The trough steady-state concentration of theophylline in plasma and stimulated saliva of 12 asthmatic children receiving an oral slow-release theophylline preparation was determined after 1 week of treatment. Plasma theophylline concentration ranged from 3.6 to 10.8 microgram/ml and saliva concentration ranged from 3.2 to 7.0 microgram/ml. There was an excellent linear relationship between theophylline concentration in plasma and stimulated saliva (r=0.89, p is less than 0.001). These observations suggest that theophylline therapy could be monitored routinely using stimulated saliva. This may be a convenient, painless and non-invasive alternative for routine monitoring of theophylline levels in asthmatic children.