Theophylline in oral mucosal transudate. A practical method for monitoring outpatient therapy

We tested the utility of a novel collection system that allows measurement of theophylline in oral mucosal transudate (OMT) to calculate serum theophylline concentrations. In 25 adult patients, theophylline levels in OMT correlated better than expectorated saliva with serum theophylline (r = 0.927 for OMT versus r = 0.831 for expectorated saliva, each p < 0.0001). In a subsequent study of 128 patients (118 adults and 10 children aged 4 to 12 yr), OMT and serum theophylline were measured and polynomial regression analysis performed to allow calculation of serum level for any given OMT level. Theophylline levels calculated from OMT values closely followed measured serum theophylline in two normal subjects after administration of either intravenous or oral theophylline. OMT samples collected by 24 patients at home were mailed to the laboratory for testing. Theophylline values from the home collection samples correlated closely (r = 0.930, p < 0.0001) with serum theophylline levels obtained at the same dose of theophylline. These findings suggest that once the relationship of serum to OMT theophylline is established in a given laboratory, the latter can be used to monitor outpatient theophylline therapy in adults (and possibly children) at times of the day otherwise inaccessible to serum sampling.